@article{de angelis_merkel_bondar_freeman_doghieri_sarti_2002, title={Gas sorption and dilation in poly(2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxole-co-tetrafluoroethylene): Comparison of experimental data with predictions of the nonequilibrium lattice fluid model}, volume={35}, ISSN={["0024-9297"]}, DOI={10.1021/ma0106090}, abstractNote={The sorption and dilation properties of a series of n-alkanes and the corresponding perfluorinated compounds have been examined in two amorphous copolymers of tetrafluoroethylene (TFE) and 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole (BDD), commercially available under the names Teflon AF1600 and AF2400. The analysis was made at three different temperatures:  25, 35, and 45 °C, to test the effect of temperature on solubility and to evaluate the sorption enthalpies. The partial molar volumes of most penetrants have also been determined in both copolymers. The experimental data have been satisfactorily compared with the sorption isotherms predicted or correlated using the nonequilibrium lattice fluid model.}, number={4}, journal={MACROMOLECULES}, author={De Angelis, MG and Merkel, TC and Bondar, VI and Freeman, BD and Doghieri, F and Sarti, GC}, year={2002}, month={Feb}, pages={1276–1288} }
 @article{digiano_roudman_arnold_freeman_2002, title={Vel block copolymers as nanofiltration materials}, volume={19}, ISSN={["1092-8758"]}, DOI={10.1089/109287502320963463}, abstractNote={The overarching goal of this research was to forge a link between materials science and engineering that may eventually lead to development of new membranes with decreased fouling tendency. Polymer structure influences water transport rates, solute partitioning, and fouling resistance. This article presents the results of testing the first generation of a novel class of nonporous block copolymers for use in nanofiltration (NF) membranes. The block copolymers comprised low surface energy fluoropolymers and highly hydrophilic hydrocarbon-based polymers. The very low surface energy of the fluoropolymer block was intended to resist adhesion of natural organic matter (NOM), a common foulant in drinking water applications of nanofiltration technology. The hydrophilic block was intended to provide channels for water permeation. Thin-film composite membrane tests with a coagulated, settled, and cartridge-filtered drinking water sample showed that the experimental membrane produced comparable water flux to a comme...}, number={6}, journal={ENVIRONMENTAL ENGINEERING SCIENCE}, author={DiGiano, FA and Roudman, A and Arnold, M and Freeman, B}, year={2002}, pages={497–511} }
 @book{baynes_riviere_smith_monteiro-riviere_freeman_2001, title={Dermal absorption cutting fluids}, journal={Annual report 1R010H03669-01A2}, author={Baynes, R. E. and Riviere, J. E. and Smith, C. E. and Monteiro-Riviere, N. A. and Freeman, B.}, year={2001}, month={May} }
 @article{serad_freeman_stewart_hill_2001, title={Gas and vapor sorption and diffusion in poly(ethylene terephthalate)}, volume={42}, ISSN={["1873-2291"]}, DOI={10.1016/S0032-3861(01)00120-3}, abstractNote={Equilibrium sorption of n-butane and acetaldehyde in melt-processed poly(ethylene terephthalate) (PET) microtomed flakes is reported. The n-butane sorption isotherm at 35°C is well described by the dual-mode model with the following parameters: kD=0.017cm3 (STP)/(cm3 amorphous polymer cmHg), C′H=1.3cm3 (STP) (cm3 amorphous polymer) and b=0.029cmHg−1. Acetaldehyde isotherms at 35 and 45°C may be described by the Flory–Huggins sorption model, suggesting that penetrant uptake in the non-equilibrium excess volume associated with the glassy polymer made a negligible contribution to the overall sorption level at the conditions of this study. The heat of sorption was essentially equal to the enthalpy of condensation of pure acetaldehyde. At 45°C and acetaldehyde pressures at or above 40.0 cmHg, acetaldehyde triggers significant crystallization of PET (up to 37 wt%) with increasing concentration. Subsequent sorption experiments at very low penetrant activity reveal solubility coefficients that are markedly higher in the penetrant-crystallized sample than in the initially highly amorphous sample. This result suggests the acetaldehyde-induced formation of microvoids (which act as highly efficient penetrant sorption sites) in the polymer sample. Based on these and literature data, the logarithm of infinite dilution penetrant solubility in amorphous regions of PET was well-correlated with penetrant condensability as characterized by Tc, penetrant critical temperature, or by (Tc/T)2, where T is the experiment temperature. Infinite dilution, amorphous phase penetrant diffusion coefficients in PET decreased according to a power law relation with increasing penetrant critical volume.}, number={16}, journal={POLYMER}, author={Serad, GE and Freeman, BD and Stewart, ME and Hill, AJ}, year={2001}, month={Jul}, pages={6929–6943} }
 @article{yampolskii_korikov_shantarovich_nagai_freeman_masuda_teraguchi_kwak_2001, title={Gas permeability and free volume of highly branched substituted acetylene polymers}, volume={34}, ISSN={["1520-5835"]}, DOI={10.1021/ma000628u}, abstractNote={Gas permeation, sorption, and structural properties of two highly branched polyacetylenes, poly[1-phenyl-2-[p-(triphenylsilyl)phenyl]acetylene] (PPhSiDPA) and poly[1-phenyl-2-[p-(triisopropylsilyl)phenyl]acetylene] (PPrSiDPA), are reported. Structurally, both polymers have much in common; however, their transport properties are quite different. PPhSiDPA has dramatically lower permeability coefficients than PPrSiDPA. For example, the O2 permeability coefficients of PPhSiDPA and PPrSiDPA are 12 × 10-10 and 230 × 10-10 cm3 (STP) cm/(cm2 s cmHg), respectively, at 22 °C. Gas solubility is very high in PPrSiDPA, similar to that observed in poly(1-trimethysilyl-1-propyne) (PTMSP), the most permeable polymer known. Gas solubility coefficients of PPhSiDPA are 2−3 times lower than those of PPrSiDPA. Free volume size and size distribution were characterized using positron annihilation lifetime (PAL) spectroscopy. Results from these studies (i.e., a bimodal size distribution of free volume elements and large free vol...}, number={6}, journal={MACROMOLECULES}, author={Yampolskii, YP and Korikov, AP and Shantarovich, VP and Nagai, K and Freeman, BD and Masuda, T and Teraguchi, M and Kwak, G}, year={2001}, month={Mar}, pages={1788–1796} }
 @article{arnold_nagai_freeman_spontak_betts_desimone_pinnau_2001, title={Gas permeation properties of poly(1,1 '-dihydroperfluorooctyl acrylate), poly(1,1 '-dihydroperfluorooetyl methacrylate), and poly(styrene)-b-poly(1,1 '-dihydroperfluorooctyl acrylate) block copolymers}, volume={34}, ISSN={["0024-9297"]}, DOI={10.1021/ma010355i}, abstractNote={The permeabilities of rubbery poly(1,1‘-dihydroperfluorooctyl acrylate) (PFOA), glassy poly(1,1‘-dihydroperfluorooctyl methacrylate) (PFOMA), and poly(styrene)-b-poly(1,1‘-dihydroperfluorooctyl acr...}, number={16}, journal={MACROMOLECULES}, author={Arnold, ME and Nagai, K and Freeman, BD and Spontak, RJ and Betts, DE and DeSimone, JM and Pinnau, I}, year={2001}, month={Jul}, pages={5611–5619} }
 @article{merkel_gupta_turk_freeman_2001, title={Mixed-gas permeation of syngas components in poly(dimethylsiloxane) and poly(1-trimethylsilyl-1-propyne) at elevated temperatures}, volume={191}, ISSN={["0376-7388"]}, DOI={10.1016/S0376-7388(01)00452-5}, abstractNote={The permeability of poly(dimethylsiloxane) (PDMS) and poly(1-trimethylsilyl-1-propyne) (PTMSP) to a simulated syngas feed containing H2, CO, CO2, and H2S was determined as a function of temperature up to 240°C (464°F). The permeation properties of rarely studied CO and H2S were found to be consistent with their molecular properties (i.e. critical temperature) in both rubbery PDMS and high free volume, glassy PTMSP. At room temperature, PDMS and PTMSP are more permeable to the more condensable gases CO2 and H2S than to H2. However, both polymers become hydrogen selective at elevated temperatures. Activation energies of permeation are highest for H2 in both polymers and decrease regularly with increasing gas condensability. PTMSP exhibits evidence of accelerated physical aging at high temperature.}, number={1-2}, journal={JOURNAL OF MEMBRANE SCIENCE}, author={Merkel, TC and Gupta, RP and Turk, BS and Freeman, BD}, year={2001}, month={Sep}, pages={85–94} }
 @article{sunderrajan_freeman_hall_pinnau_2001, title={Propane and propylene sorption in solid polymer electrolytes based on poly(ethylene oxide) and silver salts}, volume={182}, ISSN={["0376-7388"]}, DOI={10.1016/S0376-7388(00)00569-X}, abstractNote={The sorption of propylene and propane in solid polymer electrolytes based on blends of poly(ethylene oxide) (PEO) and silver nitrate, AgNO3, silver triflate, AgCF3SO3, silver trifluoroacetate, AgCF3CO2, or silver tetrafluoroborate, AgBF4, are reported. These solid polymer electrolytes exhibit preferential sorption for propylene over propane due to complexation of propylene with silver ions in the polymer matrix and reduced propane solubility in the solid polymer electrolyte films relative to that in PEO alone. The order of olefin solubility in blends containing 1 mol of silver ions per mole of ethylene oxide (EO) units is: AgBF4⪢AgCF3SO3>AgCF3CO2>AgNO3. At 35°C and 40 cmHg pressure, a PEO/AgBF4 film containing 1 mol of silver ions per mole of EO sorbed 5.3 g propylene but only 0.083 g propane per 100 g of solid polymer electrolyte. AgBF4 is highly soluble in PEO and completely disrupts polymer crystallinity even at low salt concentration (approximately 10 wt.%) without significantly altering the glass transition temperature. Other silver salts (e.g. AgNO3) do not dissolve completely in PEO and are much less effective at promoting enhanced olefin solubility.}, number={1-2}, journal={JOURNAL OF MEMBRANE SCIENCE}, author={Sunderrajan, S and Freeman, BD and Hall, CK and Pinnau, I}, year={2001}, month={Feb}, pages={1–12} }
 @article{nagai_tanaka_hirata_nakagawa_arnold_freeman_leroux_betts_desimone_digiano_2001, title={Solubility and diffusivity of sodium chloride in phase-separated block copolymers of poly(2-dimethylaminoethyl methacrylate), poly (1,1'-dihydroperfluorooctyl methacrylate) and poly(1,1,2,2-tetrahydroperfluorooctyl acrylate)}, volume={42}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(01)00549-3}, abstractNote={Solubility and diffusivity of sodium chloride were determined in a series of dense films of phase-separated diblock and triblock copolymers composed of poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) and either poly(1,1′-dihydroperfluorooctyl methacrylate (PFOMA) or poly(1,1,2,2-tetrahydroperfluorooctyl acrylate) (PTAN). As the content of hydrophilic PDMAEMA increases in PDMAEMA-b-PFOMA films, total water uptake increases. The salt partition coefficient of these films increases with increasing PDMAEMA content and weight fraction of water in the PDMAEMA domains. In contrast, salt diffusivity is not monotonically correlated with PDMAEMA content and effective hydration. Triblock copolymers exhibit different values of total water uptake, total hydration, salt partition, and diffusion coefficients than those of diblock copolymers (PDMAEMA-b-PFOMA) at the same PDMAEMA concentration. The total water uptake of PFOMA-b-PDMAEMA-b-PFOMA copolymers is lower than that of PDMAEMA-b-PFOMA, while water uptake of PTAN-b-PDMAEMA-b-PTAN films is higher than that of PDMAEMA-b-PFOMA. Salt partition and diffusion coefficients increase monotonically with the amount of freezing water in the hydrophilic domains, suggesting that the state of water in the phase-separated block copolymers is an important factor influencing their salt uptake and transport properties.}, number={25}, journal={POLYMER}, author={Nagai, K and Tanaka, S and Hirata, Y and Nakagawa, T and Arnold, ME and Freeman, BD and Leroux, D and Betts, DE and DeSimone, JM and DiGiano, FA}, year={2001}, month={Dec}, pages={9941–9948} }
 @article{dhoot_freeman_stewart_hill_2001, title={Sorption and transport of linear alkane hydrocarbons in biaxially oriented polyethylene terephthalate}, volume={39}, ISSN={["1099-0488"]}, DOI={10.1002/polb.1092}, abstractNote={Abstract}, number={11}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Dhoot, SN and Freeman, BD and Stewart, ME and Hill, AJ}, year={2001}, month={Jun}, pages={1160–1172} }
 @article{nagai_freeman_hill_2000, title={Effect of physical aging of poly(1-trimethylsilyl-1-propyne) films synthesized with TaCl5 and NbCl5 on gas permeability, fractional free volume, and positron annihilation lifetime spectroscopy parameters}, volume={38}, ISSN={["1099-0488"]}, DOI={10.1002/(SICI)1099-0488(20000501)38:9<1222::AID-POLB14>3.0.CO;2-P}, abstractNote={The effect of physical aging on the gas permeability, fractional free volume (FFV), and positron annihilation lifetime spectroscopy (PALS) parameters of dense, isotropic poly(1-trimethylsilyl-1-propyne) (PTMSP) films synthesized with TaCl5 and NbCl5 was characterized. As-cast films were soaked in methanol until an equilibrium amount of methanol was absorbed by the polymer. When the films were removed from methanol, film thickness initially decreased rapidly and was almost constant after 70 h in air for both catalysts. This timescale was much longer than the timescale for complete methanol desorption (ca. 5 h). From the film-thickness data, the reduction in FFV with time was estimated. For samples prepared with either catalyst, the kinetics of FFV reduction were well-described by a simple model based on the notion either that free-volume elements diffuse to the surface of the polymer film and are subsequently eliminated from the sample or that lattice contraction controls polymer densification. Methane permeability decreased rapidly during the first 70 h, which was the same timescale for the thickness change. The decrease in methane permeability was smaller in films prepared with NbCl5 than with TaCl5. The logarithm of methane permeability decreased linearly as reciprocal FFV increased, in accordance with free-volume theory. The PALS results indicate that the concentration of larger free-volume elements (as indicated by the intensity I4) decreased with aging time and that the other PALS parameters were not strongly influenced by aging. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1222–1239, 2000}, number={9}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Nagai, K and Freeman, BD and Hill, AJ}, year={2000}, month={May}, pages={1222–1239} }
 @article{dixon-garrett_nagai_freeman_2000, title={Ethylbenzene solubility, diffusivity, and permeability in poly(dimethylsiloxane)}, volume={38}, ISSN={["0887-6266"]}, DOI={10.1002/(SICI)1099-0488(20000601)38:11<1461::AID-POLB60>3.0.CO;2-H}, abstractNote={The pure-gas sorption, diffusion, and permeation properties of ethylbenzene in poly(dimethylsiloxane) (PDMS) are reported at 35, 45, and 55 °C and at pressures ranging from 0 to 4.4 cmHg. Additionally, mixed-gas ethylbenzene/N 2 permeability properties at 35 °C, a total feed pressure of 10 atm, and a permeate pressure of 1 atm are reported. Ethylbenzene solubility increases with increasing penetrant relative pressure and can be described by the Flory-Rehner model with an interaction parameter of 0.24 ± 0.02. At a fixed relative pressure, ethylbenzene solubility decreases with increasing temperature, and the enthalpy of sorption is -41.4 ± 0.3 kJ/mol, which is independent of ethylbenzene concentration and essentially equal to the enthalpy of condensation of pure ethylbenzene. Ethylbenzene diffusion coefficients decrease with increasing concentration at 35 °C. The activation energy of ethylbenzene diffusion in PDMS at infinite dilution is 49 ± 6 kJ/mol. The ethylbenzene activation energies of permeation decrease from near 0 to -34 ± 7 kJ/mol as concentration increases, whereas the activation energy of permeation for pure N 2 is 8 ± 2 kJ/mol. At 35 °C, ethylbenzene and N 2 permeability coefficients determined from pure-gas permeation experiments are similar to those obtained from mixed-gas permeation experiments, and ethylbenzene/N 2 selectivity values as high as 800 were observed.}, number={11}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Dixon-Garrett, SV and Nagai, K and Freeman, BD}, year={2000}, month={Jun}, pages={1461–1473} }
 @article{pinnau_freeman_2000, title={Formation and modification of polymeric membranes: Overview}, volume={744}, journal={Membrane formation and modification}, publisher={Washington, D.C.: American Chemical Society}, author={Pinnau, I. and Freeman, B. D.}, editor={I. Pinnau and Freeman, B.D.Editors}, year={2000}, pages={1–22} }
 @article{nagai_toy_freeman_teraguchi_masuda_pinnau_2000, title={Gas permeability and hydrocarbon solubility of poly[1-phenyl-2-[p-(triisopropylsilyl)phenyl]acetylene]}, volume={38}, ISSN={["0887-6266"]}, DOI={10.1002/(SICI)1099-0488(20000601)38:11<1474::AID-POLB70>3.0.CO;2-6}, abstractNote={The effects of film thickness, physical aging, and methanol conditioning on the solubility and transport properties of glassy poly[1-phenyl-2-[p-(triisopropylsilyl) phenyl]acetylene] are reported at 35 °C. In general, the gas permeability coefficients are very high, and this polymer is more permeable to larger hydrocarbons (e.g., C3H8 and C4H10) than to light gases such as H2. The gas permeability and solubility coefficients are higher in as-cast, unaged films than in as-cast films aged at ambient conditions and increase to a maximum in both unaged and aged as-cast films after methanol conditioning. For example, the oxygen permeability of a 20-μm-thick as-cast film is initially 100 barrer and decreases to 40 barrer after aging for 1 week at ambient conditions. After methanol treatment, the oxygen permeabilities of unaged and aged films increase to 430 and 460 barrer, respectively. Thicker as-cast films have higher gas permeabilities than thinner as-cast films. Propane and n-butane sorption isotherms suggest significant changes in the nonequilibrium excess free volume in these glassy polymer films due to processing history. For example, the nonequilibrium excess free volume estimated from the sorption data is similar for as-cast, unaged samples and methanol-conditioned samples; it is 100% higher in methanol-conditioned films than in aged, as-cast films. The sensitivity of permeability to processing history may be due in large measure to the influence of processing history on nonequilibrium excess free volume and free volume distribution. The propane and n-butane diffusion coefficients are also sensitive to film processing history, presumably because of the dependence of diffusivity on free volume and free volume distribution. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1474–1484, 2000}, number={11}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Nagai, K and Toy, LG and Freeman, BD and Teraguchi, M and Masuda, T and Pinnau, I}, year={2000}, month={Jun}, pages={1474–1484} }
 @article{nagai_freeman_cannon_allcock_2000, title={Gas permeability of poly(bis-trifluoroethoxyphosphazene) and blends with adamantane amino/trifluoroethoxy (50/50) polyphosphazene}, volume={172}, number={1-2}, journal={Journal of Membrane Science}, author={Nagai, K. and Freeman, B. D. and Cannon, A. and Allcock, H. R.}, year={2000}, pages={167–176} }
 @article{higuchi_yoshida_imizu_mizoguchi_he_pinnau_nagai_freeman_2000, title={Gas permeation of fullerene-dispersed poly(1-trimethylsilyl-1-propyne) membranes}, volume={38}, ISSN={["0887-6266"]}, DOI={10.1002/1099-0488(20000701)38:13<1749::AID-POLB80>3.0.CO;2-I}, abstractNote={Homogeneously fullerene-dispersed membranes were prepared under the conditions in which a 10 wt % poly(1-trimethylsilyl-1-propyne) solution containing 0.5 wt % fullerene was dried under a reduced pressure of 50 cmHg at 100 °C. UV-vis spectra and microscopic observations of the fullerene membranes indicated that the fullerene was homogeneously dispersed in the membranes. The permeability coefficients of 1-butene were found to be higher than those of n-butane in the fullerene membranes, although the permeability coefficients of olefin gases were nearly equal to those of paraffin gases having the same number of carbon in poly(1-trimethylsilyl-1-propyne) membranes containing no fullerene. Pressure dependence of permeability coefficients was clearly observed for the permeation of carbon dioxide, ethylene, ethane, 1-butene, and n-butane through the fullerene membranes, while no significant dependence was found for poly(1-trimethylsilyl-1-propyne) membranes except for the permeation of 1-butene and n-butane. The pressure dependence of the permeability was explained by the dual-mode sorption model. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1749–1755, 2000}, number={13}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Higuchi, A and Yoshida, T and Imizu, T and Mizoguchi, K and He, ZJ and Pinnau, I and Nagai, K and Freeman, BD}, year={2000}, month={Jul}, pages={1749–1755} }
 @article{merkel_bondar_nagai_freeman_pinnau_2000, title={Gas sorption, diffusion, and permeation in poly(dimethylsiloxane)}, volume={38}, ISSN={["0887-6266"]}, DOI={10.1002/(SICI)1099-0488(20000201)38:3<415::AID-POLB8>3.0.CO;2-Z}, abstractNote={The permeability of poly(dimethylsiloxane) [PDMS] to H2, O2, N2, CO2, CH4, C2H6, C3H8, CF4, C2F6, and C3F8, and solubility of these penetrants were determined as a function of pressure at 35 °C. Permeability coefficients of perfluorinated penetrants (CF4, C2F6, and C3F8) are approximately an order of magnitude lower than those of their hydrocarbon analogs (CH4, C2H6, and C3H8), and the perfluorocarbon permeabilities are significantly lower than even permanent gas permeability coefficients. This result is ascribed to very low perfluorocarbon solubilities in hydrocarbon-based PDMS coupled with low diffusion coefficients relative to those of their hydrocarbon analogs. The perfluorocarbons are sparingly soluble in PDMS and exhibit linear sorption isotherms. The Flory–Huggins interaction parameters for perfluorocarbon penetrants are substantially greater than those of their hydrocarbon analogs, indicating less favorable energetics of mixing perfluorocarbons with PDMS. Based on the sorption results and conventional lattice solution theory with a coordination number of 10, the formation of a single C3F8/PDMS segment pair requires 460 J/mol more energy than the formation of a C3H8/PDMS pair. A breakdown in the geometric mean approximation of the interaction energy between fluorocarbons and hydrocarbons was observed. These results are consistent with the solubility behavior of hydrocarbon–fluorocarbon liquid mixtures and hydrocarbon and fluorocarbon gas solubility in hydrocarbon liquids. From the permeability and sorption data, diffusion coefficients were determined as a function of penetrant concentration. Perfluorocarbon diffusion coefficients are lower than those of their hydrocarbon analogs, consistent with the larger size of the fluorocarbons. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 415–434, 2000}, number={3}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Merkel, TC and Bondar, VI and Nagai, K and Freeman, BD and Pinnau, I}, year={2000}, month={Feb}, pages={415–434} }
 @article{bondar_freeman_pinnau_2000, title={Gas transport properties of poly(ether-b-amide) segmented block copolymers}, volume={38}, ISSN={["0887-6266"]}, DOI={10.1002/1099-0488(20000801)38:15<2051::AID-POLB100>3.0.CO;2-D}, abstractNote={The permeation properties of H2, N2, and CO2 were determined at 35 °C and pressures up to 15 atm in phase-separated polyether-b-polyamide segmented block copolymers. These polymers contain poly(ethylene oxide) [PEO] or poly(tetramethylene oxide) [PTMEO] as the rubbery polyether phase and nylon-6 [PA6] or nylon-12 [PA12] as the hard polyamide phase. Extremely high values of polar (or quadrupolar)/nonpolar gas selectivities, coupled with high CO2 permeability coefficients, were observed. CO2/H2 selectivities as high as 9.8 and CO2/N2 selectivities as high as 56 were obtained in polymers with CO2 permeability coefficients of approximately 220 × 10−10 cm3(STP) cm/(cm2 s cmHg). As the amount of polyether increases, permeability increases. Gas permeability is higher in polymers with less polar constituents, PTMEO and PA12, than in those containing the more polar PEO and PA6 units. CO2/N2 and CO2/H2 selectivities are higher in polymers with higher concentrations of polar groups. These high selectivity values derive from large solubility selectivities in favor of CO2. Because CO2 is larger than H2 and has, therefore, a lower diffusion coefficient than H2, the weak size-sieving ability of the rubbery polyether phase, which is the locus of most of the gas permeation, also contributes to high CO2/H2 selectivity. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2051–2062, 2000}, number={15}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Bondar, VI and Freeman, BD and Pinnau, I}, year={2000}, month={Aug}, pages={2051–2062} }
 @article{higuchi_agatsuma_uemiya_kojima_mizoguchi_pinnau_nagai_freeman_2000, title={Preparation and gas permeation of immobilized fullerene membranes}, volume={77}, ISSN={["0021-8995"]}, DOI={10.1002/(SICI)1097-4628(20000718)77:3<529::AID-APP8>3.0.CO;2-Y}, abstractNote={Fullerene-dispersed membranes were homogeneously prepared under the conditions in which a 10 wt % polystyrene solution containing 1 wt % fullerene was dried under a reduced pressure of 50 cmHg at room temperature. The fullerene membranes prepared with 1,2-dichlorobenzene were found to have the darkest color, and showed no evidence of fullerene crystals in their photomicrographs. UV-visible and infrared absorption spectra of the fullerene membranes showed fullerene bands, which indicated that the fullerene was homogeneously dispersed in the membranes. The permeability coefficients of pure nitrogen, oxygen, carbon dioxide, ethane, and ethylene were found to increase significantly in the fullerene membranes compared to those in the polystyrene membranes, although the ideal separation factors for oxygen/nitrogen and ethylene/ethane in the fullerene membranes (i.e., 4.3 and 1.7, respectively) were slightly less than the separation factors in the polystyrene membranes. The permeability increase originated from the increase in diffusion coefficients in the fullerene membranes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 529–537, 2000}, number={3}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, author={Higuchi, A and Agatsuma, T and Uemiya, S and Kojima, T and Mizoguchi, K and Pinnau, I and Nagai, K and Freeman, BD}, year={2000}, month={Jul}, pages={529–537} }
 @article{toy_nagai_freeman_pinnau_he_masuda_teraguchi_yampolskii_2000, title={Pure-gas and vapor permeation and sorption properties of poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]acetylene] (PTMSDPA)}, volume={33}, ISSN={["1520-5835"]}, DOI={10.1021/ma991566e}, abstractNote={The pure-gas permeation and sorption properties of poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]acetylene] [PTMSDPA] are presented and compared to those of poly(1-trimethylsilyl-1-propyne) [PTMSP], poly(4-methyl-2-pentyne) [PMP], and poly(1-phenyl-1-propyne) [PPP]. PTMSDPA is more permeable to large, condensable vapors (e.g., n-butane) than to small, permanent gases (e.g., hydrogen). Such behavior is also observed in PTMSP and PMP but not in PPP. PTMSDPA has lower fractional free volume (0.26) and gas permeabilities than PTMSP and PMP. However, relative to conventional glassy polymers, PTMSDPA is a highly permeable, high free volume, glassy material. For example, the oxygen permeability coefficient of PTMSDPA is 1200 × 10-10 cm3(STP)·cm/(cm2·s·cmHg) at 25 °C. As temperature increases, the permeability in PTMSDPA increases for light gases (helium, hydrogen, and nitrogen) and decreases for more condensable gases. In contrast, the permeabilities of PTMSP and PMP decrease with increasing temperature for both lig...}, number={7}, journal={MACROMOLECULES}, author={Toy, LG and Nagai, K and Freeman, BD and Pinnau, I and He, Z and Masuda, T and Teraguchi, M and Yampolskii, YP}, year={2000}, month={Apr}, pages={2516–2524} }
 @article{merkel_bondar_nagai_freeman_2000, title={Sorption and transport of hydrocarbon and perfluorocarbon gases in poly(1-trimethylsilyl-1-propyne)}, volume={38}, ISSN={["0887-6266"]}, DOI={10.1002/(SICI)1099-0488(20000115)38:2<273::AID-POLB1>3.0.CO;2-X}, abstractNote={Pure gas solubility and permeability of H2, O2, N2, CO2, CH4, C2H6, C3H8, CF4, C2F6, and C3F8 in poly(1-trimethylsilyl-1-propyne) (PTMSP) were determined as a function of pressure at 35°C. Permeability coefficients of the perfluorinated penetrants are approximately an order of magnitude lower than those of their hydrocarbon analogs, and lower even than those of the permanent gases. In striking contrast to hydrocarbon penetrants, PTMSP permeability to fluorocarbon penetrants decreases with increasing penetrant size. This unusual size-sieving behavior in PTMSP is attributed to low perfluorocarbon solubilities in PTMSP coupled with low diffusion coefficients relative to those of their hydrocarbon analogs. In general, perfluorocarbon penetrants are less soluble than their hydrocarbon analogs in PTMSP. The difference in hydrocarbon and perfluorocarbon solubilities in high free volume, hydrocarbon-rich PTMSP is much smaller than in hydrocarbon liquids and liquidlike polydimethylsiloxane. The low solubility of perfluorocarbon penetrants is ascribed to the large size of the fluorocarbons, which inhibits their dissolution into the densified regions of the polymer matrix and reduces the number of penetrant molecules that can be accommodated in Langmuir sites. From the permeability and sorption data, diffusion coefficients were calculated as a function of penetrant concentration. With the exception of H2 and the C3 analogs, all of the penetrants exhibit a maximum in their concentration-dependent diffusion coefficients. Resolution of diffusion coefficients into a mobility factor and a thermodynamic factor reveals that it is the interplay between these two terms that causes the maxima. The mobility of the smaller penetrants (H2, O2, N2, CH4, and CO2) decreases monotonically with increasing penetrant concentration, suggesting that the net free volume of the polymer–penetrant mixture decreases as additional penetrant is added to PTMSP. For larger penetrants mobility either: (1) remains constant at low concentrations and then decreases at higher penetrant concentrations (C2H6, CF4, and C2F6); (2) remains constant for all concentrations examined (C3H8); or (3) increases monotonically with increasing penetrant concentration (C3F8). Presumably these results reflect the varying effects of these penetrants on the net free volume of the polymer–penetrant system. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 273–296, 2000}, number={2}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Merkel, TC and Bondar, V and Nagai, K and Freeman, BD}, year={2000}, month={Jan}, pages={273–296} }
 @article{dixon-garrett_nagai_freeman_2000, title={Sorption, diffusion, and permeation of ethylbenzene in poly(1- trimethylsilyl-1-propyne)}, volume={38}, DOI={10.1002/(SICI)1099-0488(20000415)38:8<1078::AID-POLB8>3.0.CO;2-2}, abstractNote={The solubility, diffusivity, and permeability of ethylbenzene in poly(1-trimethylsilyl-1-propyne) (PTMSP) at 35, 45 and 55 °C were determined using kinetic gravimetric sorption and pure gas permeation methods. Ethylbenzene solubility in PTMSP was well described by the generalized dual-mode model with χ = 0.39 ± 0.02, b = 15 ± 1, and C′H = 45 ± 4 cm3 (STP)/cm3 PTMSP at 35 °C. Ethylbenzene solubility increased with decreasing temperature; the enthalpy of sorption at infinite dilution was −40 ± 7 kJ/mol and was essentially equal to the enthalpy change upon condensation of pure ethylbenzene. The diffusion coefficient of ethylbenzene in PTMSP decreased with increasing concentration and decreasing temperature. Activation energies of diffusion were very low at infinite dilution and increased with increasing concentration to a maximum value of 50 ± 10 kJ/mol at the highest concentration explored. PTMSP permeability to ethylbenzene decreased with increasing concentration. The permeability estimated from solubility and diffusivity data obtained by kinetic gravimetric sorption was in good agreement with permeability determined from direct permeation experiments. Permeability after exposure to a high ethylbenzene partial pressure was significantly higher than that observed before the sample was exposed to a higher partial pressure of ethylbenzene. Nitrogen permeability coefficients were also determined from pure gas experiments. Nitrogen and ethylbenzene permeability coefficients increased with decreasing temperature, and infinite dilution activation energies of permeation for N2 and ethylbenzene were −5.5 ± 0.5 kJ/mol and −74 ± 11 kJ/mol, respectively. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1078–1089, 2000}, number={8}, journal={Journal of Polymer Science. Part B, Polymer Physics}, author={Dixon-Garrett, S. V. and Nagai, K. and Freeman, B. D.}, year={2000}, pages={1078–1089} }
 @article{kwak_aoki_toy_freeman_masuda_2000, title={Synthesis, characterization, and oxygen permeability of homo- and copolymers from p-[tris(trimethylsilyl)silyl]- phenylacetylene}, volume={45}, number={3}, journal={Polymer Bulletin (Berlin, Germany) (Online)}, author={Kwak, G. and Aoki, T. and Toy, L. G. and Freeman, B. D. and Masuda, T.}, year={2000}, pages={215–221} }
 @article{yampol'skii_berezkin_popova_korikov_freeman_bondar_merkel_2000, title={Thermodynamics of gas and vapor sorption by amorphous glassy AF teflons}, volume={42}, number={6}, journal={Polymer Science. Series A}, author={Yampol'skii, Y. P. and Berezkin, V. G. and Popova, T. P. and Korikov, A. P. and Freeman, B. D. and Bondar, V. I. and Merkel, T. C.}, year={2000}, pages={679–688} }
 @article{mcdowell_partin_freeman_mcneely_1999, title={Acetone solubility and diffusivity in poly(ethylene terephthalate) modified with low levels of 2,6-naphthalene dicarboxylic acid, isophthalic acid, and 2,5-bis-(4-carboxyphenyl)-1,3,4-oxadiazole}, volume={163}, ISSN={["0376-7388"]}, DOI={10.1016/S0376-7388(99)00151-9}, abstractNote={A series of random copolyesters was prepared by replacing up to 10 wt.% of the dimethyl terephthalate (DMT) in poly(ethylene terephthalate) (PET) with dimethyl 2,6-naphthalene dicarboxylate (NDC), isophthalic acid (IPA), or 2,5-bis-(4-carboxyphenyl)-1,3,4-oxadiazole (ODCA). Solution cast films of the resulting copolymers were prepared and characterized. Modification of PET with NDC and ODCA led to copolymers with glass transition temperatures higher than that of PET, while modification with IPA decreased the glass transition temperature. Copolymerization decreased crystallinity levels in all cases. The acetone solubility and acetone diffusion coefficient were determined by integral kinetic gravimetric sorption experiments at 35°C and 5.4 cm Hg acetone pressure. PET containing low levels of NDC had lower amorphous phase acetone diffusivity and solubility than PET, while PET modified with IPA had amorphous phase acetone diffusivity and acetone solubility similar to that of PET. PET modified with 5% ODCA had amorphous phase acetone diffusivity similar to that of PET, while PET modified with 10% ODCA had an amorphous phase acetone diffusivity value slightly lower than that of PET. Copolymers containing ODCA had somewhat higher acetone solubilities that PET, due mainly to the lower levels of crystallinity in the ODCA-containing polymers than in PET.}, number={1}, journal={JOURNAL OF MEMBRANE SCIENCE}, author={McDowell, CC and Partin, JM and Freeman, BD and McNeely, GW}, year={1999}, month={Oct}, pages={39–49} }
 @article{mcdowell_freeman_mcneely_1999, title={Acetone sorption and uptake kinetic in poly(ethylene terephthalate)}, volume={40}, ISSN={["1873-2291"]}, DOI={10.1016/S0032-3861(98)00403-0}, abstractNote={The sorption and kinetics of acetone uptake in solvent cast films of poly(ethylene terephthalate) are reported at 35°C for acetone pressures ranging from 0 to 7.3 cm Hg. The equilibrium sorption isotherm is well described by the dual-mode sorption model with the following parameters: kD=61 cm3(STP)/(cm3·atm), C′H=7.2cm3(STP)/cm3, and b=50 atm−1. Sorption kinetics are described using a two-stage model which incorporates both Fickian diffusion and protracted polymer structural relaxation. The characteristic time associated with the relaxation process is essentially independent of acetone concentration and has an average value of approximately 15 hours. The fraction of sorption associated with polymer relaxation increases linearly with acetone concentration in the equilibrium-densified matrix of the polymer. Acetone diffusion coefficients increase with increasing acetone concentration. The concentration dependence of the acetone diffusion coefficient is well described by the dual-mobility model if the assumption of constant diffusion coefficients in the two modes is relaxed.}, number={12}, journal={POLYMER}, author={McDowell, CC and Freeman, BD and McNeely, GW}, year={1999}, month={Jun}, pages={3487–3499} }
 @article{freeman_1999, title={Basis of permeability/selectivity tradeoff relations in polymeric gas separation membranes}, volume={32}, ISSN={["0024-9297"]}, DOI={10.1021/ma9814548}, abstractNote={Gas separation properties of polymer membrane materials follow distinct tradeoff relations:  more permeable polymers are generally less selective and vice versa. Robeson1 identified the best combinations of permeability and selectivity for important binary gas pairs (O2/N2, CO2/CH4, H2/N2, etc.) and represented these permeability/selectivity combinations empirically as αA/B = βA/B , where PA and PB are the permeability coefficients of the more permeable and less permeable gases, respectively, αA/B is selectivity (=PA/PB), and λA/B and βA/B are empirical parameters. This report provides a fundamental theory for this observation. In the theory, λA/B depends only on gas size. βA/B depends on λA/B, gas condensability, and one adjustable parameter.}, number={2}, journal={MACROMOLECULES}, author={Freeman, BD}, year={1999}, month={Jan}, pages={375–380} }
 @article{sunderrajan_freeman_hall_1999, title={Fourier transform infrared spectroscopic characterization of olefin complexation by silver salts in solution}, volume={38}, ISSN={["0888-5885"]}, DOI={10.1021/ie9900667}, abstractNote={Complex formation between 1-hexene and silver salts in chloroform solution has been characterized using Fourier transform infrared spectroscopy. Silver tetrafluoroborate, AgBF4, and silver triflate, AgCF3SO3, form 1:2 Ag+:1-hexene complexes in solution. The olefinic CC vibrational stretching frequency at 1640 cm-1 in 1-hexene shifts to approximately 1580 cm-1 upon complexation with these silver salts. Silver trifluoroacetate, AgCF3CO2, exhibits limited complexation and silver nitrate, AgNO3, exhibits no measurable complexation. Salts with the larger BF4- and CF3SO3- anions have a much stronger tendency to form complexes than those with the smaller NO3- and CF3CO2- anions. The tendency of these salts to form complexes in solution was most strongly correlated with anion size and was not well-correlated with measures of anion-donor electron density or softness parameter. The effect of ether-containing compounds, such as triethylene glycol (TEG) and poly(ethylene glycol) (PEG), on the silver−olefin interactio...}, number={10}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Sunderrajan, S and Freeman, BD and Hall, CK}, year={1999}, month={Oct}, pages={4051–4059} }
 @article{singh_ghosal_freeman_lozano_campa_abajo_1999, title={Gas separation properties of pendent phenyl substituted aromatic polyamides containing sulfone and hexafluoroisopropylidene groups}, volume={40}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(98)00800-3}, abstractNote={The synthesis and gas transport properties of aromatic polyisophthalamides (PIPAs) based on isophthaloyl chloride (IPC) derivatives bearing a pendent phenyl group and a hexafluoroisopropylidene (6F) linkage in the main chain are reported. The properties of these polymers are compared with the properties of similar PIPAs containing sulfonyl (SO2) rather than 6F in the main chain. Polymers containing a phenyl pendent group at the five position of the isophthaloyl linkage are more permeable than those bearing only a hydrogen atom at this position, although increases in permeability are generally accompanied by decreases in selectivity. In the SO2-bearing polymer, the addition of a phenyl pendent group hinders chain packing more than in the 6F containing PIPAs. Consequently, permeability coefficients increase more upon addition of a pendent phenyl group in SO2-containing rather than 6F-containing PIPAs. The effect of amide linkage reversal on the gas transport properties of a polymer containing 6F linkages in the chain backbone and a hydrogen atom at the five position of the isophthaloyl linkage was minimal. All the PIPAs considered in this study were more permeable to nitrogen than to methane, some with nitrogen/methane selectivities of more than two.}, number={20}, journal={POLYMER}, author={Singh, A and Ghosal, K and Freeman, BD and Lozano, AE and Campa, JG and Abajo, J}, year={1999}, month={Sep}, pages={5715–5722} }
 @article{bondar_freeman_pinnau_1999, title={Gas sorption and characterization of poly(ether-b-amide) segmented block copolymers}, volume={37}, DOI={10.1002/(SICI)1099-0488(19990901)37:17<2463::AID-POLB18>3.3.CO;2-8}, abstractNote={The solubilities of He, H2, N2, O2, CO2, CH4, C2H6, C3H8, and n-C4H10 were determined at 35°C and pressures up to 27 atmospheres in a systematic series of phase separated polyether–polyamide segmented block copolymers containing either poly(ethylene oxide) [PEO] or poly(tetramethylene oxide) [PTMEO] as the rubbery polyether phase and nylon 6 [PA6] or nylon 12 [PA12] as the hard polyamide phase. Sorption isotherms are linear for the least soluble gases (He, H2, N2, O2, and CH4), convex to the pressure axis for more soluble penetrants (CO2, C3H8, and n-C4H10) and slightly concave to the pressure axis for ethane. These polymers exhibit high CO2/N2 and CO2/H2 solubility selectivity. This property appears to derive mainly from high carbon dioxide solubility, which is ascribed to the strong affinity of the polar ether linkages for CO2. As the amount of the polyether phase in the copolymers increases, gas solubility increases. The solubility of all gases is higher in polymers with less polar constituents, PTMEO and PA12, than in polymers with more polar PEO and PA6 units. CO2/N2 and CO2/H2 solubility selectivity, however, are higher in polymers with higher concentrations of polar repeat units. The sorption data are complemented with physical characterization (differential scanning calorimetry, elemental analysis, and wide angle X-ray diffraction) of the various block copolymers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2463–2475, 1999}, number={17}, journal={Journal of Polymer Science. Part B, Polymer Physics}, author={Bondar, V. I. and Freeman, B. D. and Pinnau, I.}, year={1999}, pages={2463–2475} }
 @article{merkel_bondar_nagai_freeman_yampolskii_1999, title={Gas sorption, diffusion, and permeation in poly(2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole-co-tetrafluoroethylene)}, volume={32}, ISSN={["0024-9297"]}, DOI={10.1021/ma990685r}, abstractNote={The solubility and permeability of H2, O2, N2, CO2, CH4, C2H6, C3H8, CF4, C2F6, and C3F8 in TFE/BDD87, a random copolymer prepared from 87 mol % 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole [BDD] and 13 mol % tetrafluoroethylene [TFE], are reported as a function of temperature and pressure. Sorption isotherms of all penetrants except hydrogen are concave to the pressure axis and are well-described by the dual-mode model. Hydrogen exhibits linear sorption isotherms. In contrast to previous results in hydrocarbon-rich polymers, the solubility of perfluorocarbon penetrants is higher in TFE/BDD87 than that of their hydrocarbon analogues. The solubility of all penetrants in TFE/BDD87 decreases with increasing temperature. Enthalpies of sorption become more negative as penetrant size increases. Fluorocarbon enthalpies of sorption at infinite dilution are significantly more exothermic than those of their hydrocarbon analogues, suggesting more favorable interactions between fluorocarbon penetrants and perflu...}, number={25}, journal={MACROMOLECULES}, author={Merkel, TC and Bondar, V and Nagai, K and Freeman, BD and Yampolskii, YP}, year={1999}, month={Dec}, pages={8427–8440} }
 @article{de angelis_merkel_bondar_freeman_doghieri_sarti_1999, title={Hydrocarbon and fluorocarbon solubility and dilation in poly(dimethylsiloxane): Comparison of experimental data with predictions of the Sanchez-Lacombe equation of state}, volume={37}, ISSN={["0887-6266"]}, DOI={10.1002/(SICI)1099-0488(19991101)37:21<3011::AID-POLB11>3.0.CO;2-V}, abstractNote={Sorption and dilation isotherms are reported for a series of gases (N2, O2, CO2), hydrocarbon vapors (CH4, C2H6, C3H8), and their fluorocarbon analogs (CF4, C2F6, C3F8) in poly(dimethylsiloxane) (PDMS) at 35°C and pressures up to 27 atmospheres. The hydrocarbons are significantly more soluble in hydrocarbon-based PDMS than their fluorocarbon analogs. Infinite dilution partial molar volumes of both hydrocarbons and fluorocarbons in PDMS were similar to their partial molar volumes in other hydrocarbon polymers and in organic liquids. Except for C2H6 and C3H8, partial molar volume was independent of penetrant concentration. For these penetrants, partial molar volume increased with increasing concentration. The Sanchez–Lacombe equation of state is used to predict gas solubility and polymer dilation. If the Sanchez–Lacombe model is used with no adjustable parameters, solubility is always overpredicted. The extent of overprediction is more substantial for fluorocarbon penetrants than for hydrocarbons. Very good fits of the model to the experimental sorption and dilation data are obtained when the mixture interaction parameter is treated as an adjustable parameter. For the hydrocarbons, the interaction parameter is approximately 0.96, and for the fluorocarbons, it is approximately 0.87. These values suggest less favorable interactions between the hydrocarbon-based PDMS matrix and the fluorocarbon penetrants than between PDMS and hydrocarbons. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3011–3026, 1999}, number={21}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={De Angelis, MG and Merkel, TC and Bondar, VI and Freeman, BD and Doghieri, F and Sarti, GC}, year={1999}, month={Nov}, pages={3011–3026} }
 @article{merkel_bondar_nagai_freeman_1999, title={Hydrocarbon and perfluorocarbon gas sorption in poly(dimethylsiloxane), poly(1-trimethylsilyl-1-propyne), and copolymers of tetrafluoroethylene and 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole}, volume={32}, ISSN={["0024-9297"]}, DOI={10.1021/ma9814402}, abstractNote={Sorption of a series of gases, perfluorocarbon vapors (CF4, C2F6, and C3F8) and their hydrocarbon analogues in poly(dimethylsiloxane) [PDMS], poly(1-trimethylsilyl-1-propyne) [PTMSP], and two random copolymers of tetrafluoroethylene [TFE] and 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole [BDD] are reported as a function of penetrant pressure at 35 °C. Sorption isotherms for all penetrants in rubbery PDMS are linear or slightly convex to the pressure axis, while those in the glassy polymers are concave and are well described by the dual mode model. Fluorocarbon sorption levels are lower than sorption levels of their hydrocarbon analogues in the hydrocarbon-based PDMS and PTMSP matrixes, while the reverse is true in the fluorinated TFE/BDD copolymers. Exceptionally low fluorocarbon solubilities in PDMS are ascribed to poor penetrant/polymer energetic interactions.}, number={2}, journal={MACROMOLECULES}, author={Merkel, TC and Bondar, V and Nagai, K and Freeman, BD}, year={1999}, month={Jan}, pages={370–374} }
 @article{mcdowell_freeman_mcneely_1999, title={Interval kinetic gravimetric sorption of acetone in random copolymers of poly(ethylene terephthalate) and poly(ethylene 2,6-naphthalate)}, volume={37}, ISSN={["0887-6266"]}, DOI={10.1002/(SICI)1099-0488(19991101)37:21<2973::AID-POLB7>3.0.CO;2-M}, abstractNote={Interval sorption kinetics of acetone in solvent cast films of random poly(ethylene terephthalate)-co-(ethylene 2,6-naphthalate) (PET-co-PEN) are reported at 35°C and at acetone pressures ranging from 0 to 7.3 cm Hg. Polymer composition is varied systematically from 0% to 50% poly(ethylene 2,6-naphthalate). Equilibrium sorption is well described by the dual-mode sorption model. Interval sorption kinetics are described using a two-stage model that incorporates both Fickian diffusion and protracted polymer structural relaxation. The incorporation of low levels of PEN into PET significantly reduces the excess free volume associated with the glassy state and, for these interval acetone sorption experiments in ∼ 5 μm-thick films, decreases the fraction of acetone uptake controlled by penetrant-induced polymer structural relaxation.}, number={21}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={McDowell, CC and Freeman, BD and McNeely, GW}, year={1999}, month={Nov}, pages={2973–2984} }
 @article{coker_allen_freeman_fleming_1999, title={Nonisothermal model for gas separation hollow-fiber membranes}, volume={45}, ISSN={["0001-1541"]}, DOI={10.1002/aic.690450709}, abstractNote={Abstract}, number={7}, journal={AICHE JOURNAL}, author={Coker, DT and Allen, T and Freeman, BD and Fleming, GK}, year={1999}, month={Jul}, pages={1451–1468} }
 @book{freeman_pinnau_1999, title={Polymer membranes for gas and vapor separation: Chemistry and materials science}, volume={733}, ISBN={0841236054}, journal={ACS Symposium Series}, publisher={Washington, DC: American Chemical Society: distributed by Oxford University Press}, author={Freeman, B. D. and Pinnau, I.}, year={1999} }
 @article{bondar_freeman_yampolskii_1999, title={Sorption of gases and vapors in an amorphous glassy perfluorodioxole copolymer}, volume={32}, ISSN={["0024-9297"]}, DOI={10.1021/ma9817222}, abstractNote={Gas and vapor sorption properties of a random copolymer of 87 mol % 2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole and 13% tetrafluoroethylene (AF2400) are reported. Using both pressure decay and inverse gas chromatography (IGC) methods, a wide range of solutes was studied:  He, N2, O2, CO2, C1−C13 n-alkanes, CF4, C2F6, C6F6, and C6F5CF3. These solutes have critical temperatures ranging from 5 to 677 K. AF2400 has very large solubility coefficients, S, relative to other glassy and rubbery polymers. Only poly(1-trimethylsilyl-1-propyne), the most permeable polymer known, exhibits higher solubility coefficients. The large solubility coefficients in AF2400 are mainly due to high Henry's law solubility coefficients. Fluorocarbon solutes exhibit higher solubility than their hydrocarbon analogues. A novel linear correlation between the logarithm of S and Tc2, where Tc is the solute critical temperature, was observed. On the basis of IGC results, the microcavity size in this perfluoropolymer is larger than in...}, number={19}, journal={MACROMOLECULES}, author={Bondar, VI and Freeman, BD and Yampolskii, YP}, year={1999}, month={Sep}, pages={6163–6171} }
 @article{yampolskii_motyakin_wasserman_masuda_teraguchi_khotimskii_freeman_1999, title={Study of high permeability polymers by means of the spin probe technique}, volume={40}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(98)00395-4}, abstractNote={The spin probe technique was systematically applied to study a family of high permeability and high free volume glassy polymers. Rotation correlation times τc or frequencies ν=1/τc of 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO) were measured in amorphous teflons — random copolymers of tetrafluoroethylene and 2,2-bistrifluoromethyle-4,5-difluoro-1,3-dioxole, polyacetylenes and polynorbornenes. Polymers distinguished by unusually high, for the glassy state, permeability and free volume exhibit large rotational mobility of TEMPO. The correlation times correspond to fast rotation of the spin probe previously observed only in rubbery polymers. Correlations between the frequency ν and gas permeability and diffusion coefficients were observed. However, in some polymers, the spin probe's rotation rate is also sensitive to side-chain local mobility, which does not affect translational diffusion coefficients of gas molecules in polymers.}, number={7}, journal={POLYMER}, author={Yampolskii, YP and Motyakin, MV and Wasserman, AM and Masuda, T and Teraguchi, M and Khotimskii, VS and Freeman, BD}, year={1999}, month={Mar}, pages={1745–1752} }
 @article{havelka-rivard_nagai_freeman_sheares_1999, title={Synthesis and characterization of poly[[1,1 '-biphenyl]-4,4 '- diyl[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]]}, volume={32}, number={20}, journal={Macromolecules}, author={Havelka-Rivard, P. A. and Nagai, K. and Freeman, B. D. and Sheares, V. V.}, year={1999}, pages={6418–6424} }
 @article{cantrell_mcdowell_freeman_noel_1999, title={The influence of annealing on thermal transitions in a nematic copolyester}, volume={37}, DOI={10.1002/(SICI)1099-0488(19990315)37:6<505::AID-POLB3>3.0.CO;2-9}, abstractNote={Thermal transitions of a glassy, main chain, liquid crystalline, random copolyester, HIQ-40, have been characterized. HIQ-40 is made from 40 mol percent p-hydroxybenzoic acid (HBA) and 30 mol % each of p-hydroquinone (HQ) and isophthalic acid (IA). This polymer is soluble in organic solvents, permitting the preparation of thin, solution-cast films that are in a glassy, metastable, optically isotropic state. On first heating of an isotropic HIQ-40 film in a calorimeter, one glass transition is observed at low temperature (approximately 42°C), and is ascribed to the glass/rubber transition of the isotropic polymer. A cold crystallization exotherm centered near 150°C is observed. This is associated with the development of low levels of crystalline order. A broad melting endotherm is centered at about 310°C; this endotherm marks the melting of crystallites and the transformation to a nematic fluid. A nematic to isotropic transition was not observed by calorimetry. After quenching from the nematic melt, a T g is observed in the range of 110-115°C and is associated with the glass/rubber transition of the nematically ordered polymer. Annealing optically isotropic films at temperatures above the isotropic glass transition results in the systematic development of axial order. In these annealed samples, T g increases rapidly until it is near the annealing temperature, then T g increases more slowly at longer annealing times. In as-cast films annealed at 120-135°C, the light intensity transmitted through a sample held between crossed polarizers in an optical microscope (a qualitative measure of birefringence and, in turn, axial order) initially increases rapidly and uniformly throughout the sample and, at longer annealing times, approaches asymptotic values that are higher at higher annealing temperatures. The increase in transmitted intensity is ascribed to the development of axial order. The uniform increase in transmitted intensity suggests that ordering occurs by a rather global process and not via a nucleation and growth mechanism.}, number={6}, journal={Journal of Polymer Science. Part B, Polymer Physics}, author={Cantrell, G. R. and McDowell, C. C. and Freeman, B. D. and Noel, C.}, year={1999}, pages={505–522} }
 @article{mcdowell_coker_freeman_1998, title={An automated spring balance for kinetic gravimetric sorption of gases and vapors in polymers}, volume={69}, ISSN={["0034-6748"]}, DOI={10.1063/1.1148456}, abstractNote={A method for automation of a McBain-type spring balance using a charge coupled device camera, a computer equipped with a frame-grabber card, and National Institutes of Health Image software is presented. This balance is used to study the sorption and transport of small molecules in polymeric materials. Kinetic gravimetric sorption data of acetone uptake in a random copolymer of 50 wt % poly(ethylene terephthalate) and 50 wt % poly(ethylene 2,6-naphthalate) at 35 °C are provided to illustrate the utility of the method. The diffusion coefficients determined from the cathetometer and camera experiments are 1.1±0.2×10−12 and 1.0±0.2×10−12 cm2/s, respectively. At an acetone partial pressure of 5.4 cm Hg, the equilibrium acetone uptake was 1.47±0.15 g acetone/100 g polymer using the cathetometer to determine spring extension and 1.52±0.15 g acetone/100 g polymer when the camera was used to determine mass uptake of acetone by the polymer. The camera-based balance was determined to be sensitive to weight changes as small as ±1 μg.}, number={6}, journal={REVIEW OF SCIENTIFIC INSTRUMENTS}, author={McDowell, CC and Coker, DT and Freeman, BD}, year={1998}, month={Jun}, pages={2510–2513} }
 @article{coker_freeman_fleming_1998, title={Modeling multicomponent gas separation using hollow-fiber membrane contactors}, volume={44}, ISSN={["0001-1541"]}, DOI={10.1002/aic.690440607}, abstractNote={Abstract}, number={6}, journal={AICHE JOURNAL}, author={Coker, DT and Freeman, BD and Fleming, GK}, year={1998}, month={Jun}, pages={1289–1302} }
 @article{huang_durning_freeman_1998, title={Modeling weakly non-linear two-stage sorption kinetics in glassy polymer films}, volume={143}, ISSN={["0376-7388"]}, DOI={10.1016/S0376-7388(97)00291-3}, abstractNote={A model for non-Fickian gradient diffusion in polymer–penetrant systems is studied to assess its capability in predicting experimental results in weakly non-linear differential vapor sorption experiments at conditions where “two-stage” sorption kinetics occur. The effects of six dimensionless parameters in the model on predictions of sorption kinetics are evaluated systematically by numerical simulations. The model predicts a number of observable trends. The predictions are compared successfully with sorption data of acetone vapor in VECTRA®, a glassy random copolyester of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (HBA/HNA). The results are relevant to the application of VECTRA® and related polymers as barrier materials.}, number={1-2}, journal={JOURNAL OF MEMBRANE SCIENCE}, author={Huang, SJ and Durning, CJ and Freeman, BD}, year={1998}, month={May}, pages={1–11} }
 @article{singh_freeman_pinnau_1998, title={Pure and mixed gas acetone/nitrogen permeation properties of polydimethylsiloxane [PDMS]}, volume={36}, ISSN={["0887-6266"]}, DOI={10.1002/(SICI)1099-0488(19980130)36:2<289::AID-POLB8>3.0.CO;2-M}, abstractNote={The permeability of polydimethylsiloxane [PDMS] to acetone, nitrogen, and acetone/nitrogen mixtures has been determined at 28°C. In pure gas experiments, the permeability of PDMS to nitrogen was 245 × 10−10 cm3(STP) · cm/cm2 · s · cmHg and was independent of pressure. The permeability of PDMS to acetone vapor increased exponentially with increasing acetone pressure. PDMS is much more permeable to acetone than to nitrogen; acetone/nitrogen selectivity increases from 85 to 185 as acetone partial pressure in the feed increases from 0 to 67% of saturation. In mixed gas permeation experiments, the nitrogen permeability coefficient is independent of acetone relative pressure and is equal to the pure gas permeability coefficient. The acetone permeability coefficient has the same value in both mixed gas and pure acetone permeation experiments. Average acetone diffusivity in PDMS, determined as the ratio of permeability to solubility, decreases with increasing acetone concentration due to mild clustering of acetone in the polymer (because acetone is a poor solvent for PDMS) and changes in the polymer–penetrant thermodynamic interactions which influence diffusion coefficients. A Zimm–Lundberg analysis of the acetone sorption isotherm is also consistent with acetone clustering in PDMS. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 289–301, 1998}, number={2}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Singh, A and Freeman, BD and Pinnau, I}, year={1998}, month={Jan}, pages={289–301} }
 @article{mcdowell_freeman_mcneely_haider_hill_1998, title={Synthesis, physical characterization, and acetone sorption kinetics in random copolymers of poly(ethylene terephthalate) and poly(ethylene 2,6-naphthalate)}, volume={36}, ISSN={["1099-0488"]}, DOI={10.1002/(SICI)1099-0488(19981130)36:16<2981::AID-POLB13>3.0.CO;2-N}, abstractNote={Random copolymers of poly(ethylene terephthalate) (PET) and poly(ethylene 2,6-naphthalate) (PEN) were synthesized by melt condensation. In a series of thin, solvent cast films of varying PEN content, acetone diffusivity and solubility were determined at 35°C and an acetone pressure of 5.4 cm Hg. The kinetics of acetone sorption in the copolymer films are well described by a Fickian model. Both solubility and diffusivity decrease with increasing PEN content. The acetone diffusion coefficient decreases 93% from PET to PET/85PEN, a copolymer in which 85 weight percent of the dimethyl terephthalate in PET has been replace by dimethyl naphthalate 2,6-dicarboxylate. The acetone solubility coefficient in the amorphous regions of the polymer decreases by approximately a factor of two over the same composition range. The glass/rubber transition temperatures of these materials rise monotonically with increasing PEN content. Copolymers containing 20 to 80 wt % PEN are amorphous. Samples with 80% PEN contain measurable levels of crystallinity. Estimated fractional free volume in the amorphous regions of these samples is lower in the copolymers than in either of the homopolymers. Relative free volume as probed by positron annihilation lifetime spectroscopy (PALS) decreases systematically with increasing PEN content. Acetone diffusion coefficients correlate well with PALS results. Infrared spectroscopy suggests an increase in the fraction of ethylene glycol units in the trans conformation in the amorphous phase as the concentration of PEN in the copolymer increases. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2981–3000, 1998}, number={16}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={McDowell, CC and Freeman, BD and McNeely, GW and Haider, MI and Hill, AJ}, year={1998}, month={Nov}, pages={2981–3000} }
 @article{toy_freeman_spontak_morisato_pinnau_1997, title={Gas permeability and phase morphology of poly(1-(trimethylsilyl)-1-propyne)/poly(1-phenyl-1-propyne) blends}, volume={30}, ISSN={["0024-9297"]}, DOI={10.1021/ma970091t}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTGas Permeability and Phase Morphology of Poly(1-(trimethylsilyl)-1-propyne)/Poly(1-phenyl-1-propyne) BlendsLora G. Toy, Benny D. Freeman, Richard J. Spontak, Atsushi Morisato, and Ingo PinnauView Author Information Departments of Chemical Engineering and Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 Membrane Technology and Research, Inc., 1360 Willow Road, Suite 103, Menlo Park, California 94025 Cite this: Macromolecules 1997, 30, 16, 4766–4769Publication Date (Web):August 11, 1997Publication History Received22 January 1997Revised19 May 1997Published online11 August 1997Published inissue 1 August 1997https://doi.org/10.1021/ma970091tCopyright © 1997 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views362Altmetric-Citations29LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (146 KB) Get e-AlertsSUBJECTS:Colloids,Interface engineering,Permeability,Selectivity,Transmission electron microscopy Get e-Alerts}, number={16}, journal={MACROMOLECULES}, author={Toy, LG and Freeman, BD and Spontak, RJ and Morisato, A and Pinnau, I}, year={1997}, month={Aug}, pages={4766–4769} }
 @article{pinnau_casillas_morisato_freeman_1997, title={Long-term permeation properties of poly(1-trimethylsilyl-1-propyne) membranes in hydrocarbon-vapor environment}, volume={35}, ISSN={["0887-6266"]}, DOI={10.1002/(SICI)1099-0488(19970730)35:10<1483::AID-POLB2>3.0.CO;2-T}, abstractNote={Poly(1-trimethylsilyl-1-propyne) (PTMSP), a high free-volume glassy di-substituted polyacetylene, has the highest gas permeabilities of all known polymers. The high gas permeabilities in PTMSP result from its very high excess free volume and connectivity of free volume elements. Permeability coefficients of permanent gases in PTMSP decrease dramatically over time due to loss of excess free volume. The effects of aging on gas permeability and selectivity of PTMSP membranes continuously exposed to a 2 mol % n-butane/98 mol % hydrogen mixture over a period of 47 days are reported. The permeation properties of PTMSP membranes are quite stable when the polymer is continuously exposed to a gas mixture containing a highly sorbing organic vapor such af n-butane. The n-butane/hydrogen selectivity was essentially constant for the 47-day test period at a value of 29, or 88% of the initial value of the as-cast film of 33. Condensable gases such as n-butane may serve as a “filler” in the nonequilibrium free volume of the polymer, thereby preserving the high level of excess free volume. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1483–1490, 1997}, number={10}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Pinnau, I and Casillas, CG and Morisato, A and Freeman, BD}, year={1997}, month={Jul}, pages={1483–1490} }
 @article{smith_hall_freeman_1997, title={Molecular dynamics for polymeric fluids using discontinuous potentials}, volume={134}, ISSN={["0021-9991"]}, DOI={10.1006/jcph.1996.5510}, abstractNote={Molecular dynamics simulation techniques for systems interacting with discontinuous potentials are discussed. Optimization and efficiency techniques are summarized for performing discontinuous molecular dynamics on serial computers with direct application to polymer-like fluids. Comparisons are presented for two algorithms: (1) single-event scheduling, and (2) multiple-event scheduling. The single-event scheduling algorithm is approximately 75% faster than the multiple-event scheduling algorithm for molecular fluids but yields equivalent performance for atomic fluids. For the single-event scheduling method, a combination of link lists and neighbor lists are used when searching for possible particle interactions. The combination of efficiency techniques permits multibillion time step simulations for relatively large systems on desktop workstations. Both discontinuous molecular dynamics codes for single and multiple-event scheduling algorithms are available on the Internet. The utility of the method is demonstrated for entangled chains, tethered chains, and heteronuclear chain mixtures.}, number={1}, journal={JOURNAL OF COMPUTATIONAL PHYSICS}, author={Smith, SW and Hall, CK and Freeman, BD}, year={1997}, month={Jun}, pages={16–30} }
 @article{smith_freeman_hall_1997, title={Pressure-dependent photon correlation spectroscopic investigation of poly(propylene oxide) near the glass transition}, volume={30}, ISSN={["0024-9297"]}, DOI={10.1021/ma960408+}, abstractNote={The effect of pressure on structural relaxations in poly(propylene oxide) (PPO; MW = 4000) near the glass transition has been determined using photon correlation spectroscopy. Experimental results are reported for pressures ranging from 2.5 to 3.9 kbar at 253 K. The structural relaxation exhibits two distinct processes separated by ∼3 orders of magnitude in time. This observation is consistent with results of dielectric relaxation studies of PPO. The faster relaxation is associated with local segmental motions important in the glass-rubber transition. The mean relaxation time for the faster process exhibits an exponential dependence on pressure.}, number={7}, journal={MACROMOLECULES}, author={Smith, SW and Freeman, BD and Hall, CK}, year={1997}, month={Apr}, pages={2052–2057} }
 @article{sunderrajan_hall_freeman_1997, title={Sorption isotherms for spherical penetrants in facilitating polymeric media using Monte Carlo simulations}, volume={92}, ISSN={["0026-8976"]}, DOI={10.1080/002689797170671}, abstractNote={Grand canonical ensemble Monte Carlo simulations of penetrant sorption in polymeric media have been used to predict sorption isotherms as a function of polymer–penetrant interactions. The polymer is modelled as a collection of hard chains and as a collection of square-well chains, while the penetrant is modelled as hard spheres and as square-well spheres. Partition coefficients have been compared for the different potentials of interaction for stationary and moving polymeric media. Partition coefficients are found to increase with increasing reservoir penetrant pressure and to be higher in moving polymeric media than in stationary polymeric media. Partitioning was studied also as a function of concentration of facilitating sites which have an increased affinity for penetrants. Partition coefficients increased with increasing concentration of facilitating sites. The presence of a second penetrant species of normal affinity is found to affect the partitioning of species with a special affinity for facilitat...}, number={1}, journal={MOLECULAR PHYSICS}, author={Sunderrajan, S and Hall, CK and Freeman, BD}, year={1997}, month={Sep}, pages={109–116} }