@article{jayarathna_zhang_novak_2021, title={Cyclopolymerization of 1,2-Dicarbodiimides}, volume={54}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.1c00477}, abstractNote={Intramolecular cyclopolymerizations have been achieved by the polymerization of 1,2-dicarbodiimides using a CpTiCl2OCH2CF3 catalyst. Here, we have extended the living polymerization approach of monocarbodiimide polymerization using Ti(IV)-based initiators into dicarbodiimide polymerization. Polymerization occurs via an alternating intra-intermolecular cyclization and monomer addition to form polymers with this new architecture. Cyclopolymerization was carried out by tethering two neighboring carbodiimide functional groups with two- and three-carbon linkers in order to favor the intramolecular cyclization within the backbone. Linkers greater than three carbons lead to cross-linked networks. We believe these cyclopolymers contain both five- and seven-membered rings. Using enantiomerically pure monomers, e.g., trans-1,2 cyclohexyl linkers, cyclopolycarbodiimides that possess chiral conformations can be synthesized. With imparting cyclic structures along the polymer backbone, these cyclopolymers possess significant contrast compared to their acyclic polymers of carbodiimides.}, number={15}, journal={MACROMOLECULES}, author={Jayarathna, Chamni U. and Zhang, Ying and Novak, Bruce M.}, year={2021}, month={Aug}, pages={7134–7139} }
 @article{kennemur_kilgore_novak_2011, title={Adjusting Conformational Switching Behavior of Helical Polycarbodiimides Through Substituent Induced Polarity Effects}, volume={49}, ISSN={["1099-0518"]}, DOI={10.1002/pola.24484}, abstractNote={Abstract}, number={3}, journal={JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY}, author={Kennemur, Justin G. and Kilgore, Chris A. and Novak, Bruce M.}, year={2011}, month={Feb}, pages={719–728} }
 @article{kennemur_novak_2011, title={Advances in polycarbodiimide chemistry}, volume={52}, ISSN={["1873-2291"]}, DOI={10.1016/j.polymer.2011.02.040}, abstractNote={Over the last 15 years, large strides have been taken with regards to synthesis, catalysis, structural control, and functional application of polycarbodiimides (polyguanidines); a unique class of helical macromolecules that are derived from the polymerization of carbodiimide monomers using transition metal catalysis. This manuscript will provide a summary of the synthesis and characterization studies in addition to the large variety of properties discovered for these systems and potential applications associated with these properties. In large part, it is the chiral helical backbone coupled with synthetically selective pendant groups which has allowed creation of polycarbodiimides spanning a large range of potential applications. Such applications include cooperative chiral materials, liquid crystalline materials, optical sensors and display materials, tunable polarizers, sites for asymmetric catalysis, and recyclable polymers. Manipulation of the two pendant groups that span away from the amidine backbone repeat unit has allowed solubility of these polymers in solvents ranging from cyclohexane to water, maximizing the potential application of these polymers in various media.}, number={8}, journal={POLYMER}, author={Kennemur, Justin G. and Novak, Bruce M.}, year={2011}, month={Apr}, pages={1693–1710} }
 @misc{kennemur_novak_2011, title={Hierarchical Chirality in Polycarbodiimides}, volume={51}, ISSN={["1869-5868"]}, DOI={10.1002/ijch.201100030}, abstractNote={Abstract}, number={10}, journal={ISRAEL JOURNAL OF CHEMISTRY}, author={Kennemur, Justin G. and Novak, Bruce M.}, year={2011}, month={Nov}, pages={1041–1051} }
 @article{peng_desousa_su_novak_nevzorov_garland_melander_2011, title={Inhibition of Acinetobacter baumannii biofilm formation on a methacrylate polymer containing a 2-aminoimidazole subunit}, volume={47}, number={17}, journal={Chemical Communications (Cambridge, England)}, author={Peng, L. L. and DeSousa, J. and Su, Z. M. and Novak, B. M. and Nevzorov, A. A. and Garland, E. R. and Melander, C.}, year={2011}, pages={4896–4898} }
 @article{kennemur_desousa_martin_novak_2011, title={Reassessing the Regioregularity of N-(1-Naphthyl)-N '-(n-octadecyl)polycarbodiimide Using Solution Infrared Spectroscopy}, volume={44}, ISSN={["0024-9297"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79959426990&partnerID=MN8TOARS}, DOI={10.1021/ma2005052}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVNoteReassessing the Regioregularity of N-(1-Naphthyl)-N′-(n-octadecyl)polycarbodiimide Using Solution Infrared SpectroscopyJustin G. Kennemur, Joseph D. DeSousa, James D. Martin, and Bruce M. Novak*View Author Information Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695, United StatesE-mail: [email protected]Cite this: Macromolecules 2011, 44, 12, 5064–5067Publication Date (Web):May 25, 2011Publication History Received7 March 2011Revised11 May 2011Published online25 May 2011Published inissue 28 June 2011https://doi.org/10.1021/ma2005052Copyright © 2011 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views819Altmetric-Citations5LEARN 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 (2 MB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Absorption,Monomers,Polymer solutions,Polymers,Thin films Get e-Alerts}, number={12}, journal={MACROMOLECULES}, author={Kennemur, Justin G. and DeSousa, Joseph D. and Martin, James D. and Novak, Bruce M.}, year={2011}, month={Jun}, pages={5064–5067} }
 @article{walker_budhathoki-uprety_novak_muddiman_2011, title={Stable-Isotope Labeled Hydrophobic Hydrazide Reagents for the Relative Quantification of N-Linked Glycans by Electrospray Ionization Mass Spectrometry}, volume={83}, ISSN={["1520-6882"]}, url={http://dx.doi.org/10.1021/ac201376q}, DOI={10.1021/ac201376q}, abstractNote={This study presents the development of stable-isotope labeled hydrophobic, hydrazide reagents for the relative quantification of N-linked glycans. The P2GPN "light" ((12)C) and "heavy" ((13)C(6)) pair are used to differentially label two N-linked glycan samples. The samples are combined 1:1, separated using HILIC, and then mass differentiated and quantified using mass spectrometry. These reagents have several benefits: (1) impart hydrophobic character to the glycans affording an increase in electrospray ionization efficiency and MS detection; (2) indistinguishable chromatographic, MS, and MS/MS performance of the "light" and "heavy" reagents affording relative quantification; and (3) analytical variability is significantly reduced due to the two samples being mixed together after sample preparation. Obtaining these analytical benefits only requires ~4 h of sample preparation time. It is shown that these reagents are capable of quantifying changes in glycosylation in simple mixtures, and the analytical variability of the reagents in pooled plasma samples is shown to be less than ±30%. Additionally, the incorporation of an internal standard allows one to account for the difference in systematic error between the two samples due to the samples being processed in parallel and not mixed until after derivatization.}, number={17}, journal={ANALYTICAL CHEMISTRY}, author={Walker, S. Hunter and Budhathoki-Uprety, Januka and Novak, Bruce M. and Muddiman, David C.}, year={2011}, month={Sep}, pages={6738–6745} }
 @article{budhathoki-uprety_novak_2011, title={Synthesis of Alkyne-Functionalized Helical Polycarbodiimides and their Ligation to Small Molecules using 'Click' and Sonogashira Reactions}, volume={44}, ISSN={["0024-9297"]}, url={http://dx.doi.org/10.1021/ma200960e}, DOI={10.1021/ma200960e}, abstractNote={New terminal alkyne side chain functionalized polycarbodiimides, have been synthesized and “alkyne” ligation tools—“click” (copper-catalyzed Huisgen 1,3-dipolar cycloaddition reaction) and Sonogashira couplings—were utilized to create functional polymers in one step postpolymerization modifications. Polycarbodiimides are interesting synthetic, helical, nanodimensional scaffolds that are capable of presenting a variety of functional groups in highly regular periodic fashion. Herein, we report the synthesis of the first alkyne substituted polycarbodiimides, Poly-1, Poly-2, and Poly-3 and the quantitative coupling of functional azides to the alkyne repeat units of these polymers, as evidenced by IR and 1H NMR and 13C NMR spectra. We are able to couple benzyl azide, carboxylic acid azide, and N-Boc amine azide by “click” and N-Boc-l-phenylalanine by Sonogashira reactions to the alkyne side chain of Poly 1 to provide Poly-1a, -1b, -1c and -1phe, respectively. Poly-1b and Poly-1c provide peptide-coupling sites ...}, number={15}, journal={MACROMOLECULES}, author={Budhathoki-Uprety, Januka and Novak, Bruce M.}, year={2011}, month={Aug}, pages={5947–5954} }
 @article{kennemur_clark_tian_novak_2010, title={A New, More Versatile, Optical Switching Helical Polycarbodiimide Capable of Thermally Tuning Polarizations +/- 359 degrees}, volume={43}, ISSN={["1520-5835"]}, DOI={10.1021/ma902657d}, abstractNote={An in depth study of newly synthesized polycarbodiimides containing asymmetric aryl pendant groups has been performed. The focus of this study was to create new polymers capable of the low-energy, reversible, solvo-, and thermocontrollable conformational switching phenomenon previously discovered. Of the polymers synthesized, one polymer, N-(1-naphthyl)-N′-(n-octadecyl) polycarbodiimide, Poly-5, has been found to undergo reversible optical switching in various solvents, each of which alter the temperature at which the switching is observed. The switching is not due to helical inversions, but instead due to synchronous rearrangement of polyarene pendant groups around the helical backbone. This is further shown by anisotropic changes of the aromatic chemical shifts using variable temperature 1H NMR through the observed thermal switching range in THF-d8. The net change in specific optical rotation reaches a remarkable 1700° and changes in the direction of rotation. The polymer system is tunable and capable o...}, number={4}, journal={MACROMOLECULES}, author={Kennemur, Justin G. and Clark, J. B. and Tian, Gonglu and Novak, Bruce M.}, year={2010}, month={Feb}, pages={1867–1873} }
 @article{budhathoki-uprety_novak_2010, title={Synthesis of a pyridine substituted polycarbodiimide and its use as a solid support for chemical reagents}, volume={51}, ISSN={["1873-2291"]}, url={http://dx.doi.org/10.1016/j.polymer.2010.03.011}, DOI={10.1016/j.polymer.2010.03.011}, abstractNote={Abstract Optically active, polycarbodiimides 3(a, b & c) with pyridine pendant groups were synthesized using [(R) – 2,2′- binaphthoxy] (di-isopropoxy) titanium(IV) catalyst. The polymers were characterized by 1H and 13C NMR, and IR. Thermal stability of these polymers (up to 162 °C by TGA), allows thermally demanding chemical transformations on their side chains without decomposition. Advantages include fine-tunability of the other pendant group of the carbodiimide monomer. This allows one to optimize the properties of the polymer without undergoing copolymerization or further post-polymerization modifications. Borane (BH3) was coordinated to poly 3 (a & b) to prepare the functional polymers 4 (a & b) respectively. A strong IR signature peak at 2368 cm−1 supports BH3 coordination. Gravimetric analysis indicates 97–99% borane complexation of the pyridine units. In addition, the thermal stability increased to 194 °C in poly 4a is consistent with the incorporation of BH3 to the pendant pyridine of the helical polycarbodiimide 3a. Poly 4 (a & b) can be used as supported reagents and successfully reduced the carbonyl compounds (5 a–e) in moderate to excellent yields (60–100%) and are shown to be efficient, non-volatile, stable, and mild supported-reducing reagents. Upon completion of the reduction reaction, the polymer support was quantitatively recycled as required for a green solid catalyst support.}, number={10}, journal={POLYMER}, author={Budhathoki-Uprety, Januka and Novak, Bruce M.}, year={2010}, month={May}, pages={2140–2146} }
 @misc{novak_tang_2009, title={Devices containing chiroptical switching materials and methods of making and using the same}, volume={7,485,740}, number={2009 Feb. 3}, author={Novak, B. M. and Tang, H. Z.}, year={2009} }
 @article{jeong_an_kang_nguyen_lee_novak_2008, title={Synthesis of polylactide using a zinc complex containing (S)-N-ethyl-N-phenyl-2-pyrrolidinemethanamine}, volume={27}, ISSN={["0277-5387"]}, DOI={10.1016/j.poly.2007.09.021}, abstractNote={The reaction between ZnCl2 and (S)-N-ethyl-N-phenyl-2-pyrrolidinemethanamine (S-EPP) as a chiral ligand affords [ZnCl2(S-EPP)], whose structure has been determined by X-ray crystallography. [ZnEt2(S-EPP)] has demonstrated high activity toward the polymerization of rac-lactide with a maximum turnover frequency (TOF) of 121. Despite the intended stereocontrol by employing a chiral ligand, however, the observed heterotacticity was limited to under 0.6. The MWDs of the PLAs were found to be modulated by changing the solvent or controlling the concentration of the monomer in the solution. The glass transition temperature (Tg) was critically dependent on the MW within the narrow MWD regime, but the dependence became significantly shallow when the MWD was broadened.}, number={1}, journal={POLYHEDRON}, author={Jeong, Jong Hwa and An, Young Hun and Kang, Youn K. and Nguyen, Quang Trung and Lee, Hyosun and Novak, Bruce M.}, year={2008}, month={Jan}, pages={319–324} }
 @article{tang_garland_novak_he_polavarapu_sun_sheiko_2007, title={Helical polyguanidines prepared by helix-sense-selective polymerizations of achiral carbodiimides using enantiopure binaphthol-based titanium catalysts}, volume={40}, ISSN={["1520-5835"]}, DOI={10.1021/ma0618777}, abstractNote={The polymerization of N-(n-hexyl)-N‘-phenylcarbodiimide was studied using a number of homochiral catalysts based on binaphthol derivatives. All polymers showed optical activity due to the formation of a predominant screw sense controlled by the chirality of the catalyst. The helicity and chirality of these materials were studied by VCD, ECD, and polarimetry. Structures calculated using density functional theory were used to compare with their simulated VCD and experimental VCD, thus allowing the absolute screw sense to be determined. AFM imaging showed epitaxial ordering of these rigid chains on graphite surfaces and single chains measuring nearly 3 mm were observed in spin-cast samples on silicon.}, number={10}, journal={MACROMOLECULES}, author={Tang, Hong-Zhi and Garland, Eva R. and Novak, Bruce M. and He, Jiangtao and Polavarapu, Prasad L. and Sun, Frank Chen and Sheiko, Sergei S.}, year={2007}, month={May}, pages={3575–3580} }
 @article{kwark_kim_novak_2007, title={Titanium complexes: A possible catalyst for controlled radical polymerization}, volume={15}, DOI={10.1007/BF03218749}, number={1}, journal={Macromolecular Research}, author={Kwark, Y. J. and Kim, J. and Novak, B. M.}, year={2007}, pages={31–38} }
 @article{seto_novak_2006, title={Circumventing pericyclic reactions to realize insertion polymerization of cyclobutene derivatives}, volume={39}, ISSN={["0024-9297"]}, DOI={10.1021/ma0616413}, abstractNote={ADVERTISEMENT RETURN TO ISSUECommunication to the...Communication to the EditorNEXTCircumventing Pericyclic Reactions To Realize Insertion Polymerization of Cyclobutene DerivativesKeitaro Seto and Bruce M. NovakView Author Information Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695 Cite this: Macromolecules 2006, 39, 20, 6785–6788Publication Date (Web):August 31, 2006Publication History Received20 July 2006Revised14 August 2006Published online31 August 2006Published inissue 1 October 2006https://doi.org/10.1021/ma0616413Copyright © 2006 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views484Altmetric-Citations2LEARN 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 (54 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Catalysts,Hydrocarbons,Monomers,Polymerization,Polymers Get e-Alerts}, number={20}, journal={MACROMOLECULES}, author={Seto, Keitaro and Novak, Bruce M.}, year={2006}, month={Oct}, pages={6785–6788} }
 @misc{kuwahara_novak_2006, title={Stereoregular polar vinyl polymers and methods of making the same}, volume={7,091,293}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Kuwahara, H. and Novak, B.}, year={2006} }
 @article{tang_novak_he_polavarapu_2005, title={A thermal and solvocontrollable cylindrical nanoshutter based on a single screw-sense helical polyguanidine}, volume={44}, ISSN={["1521-3773"]}, DOI={10.1002/anie.200501977}, abstractNote={Helix-sense-selective polymerization of an achiral carbodiimide using a chiral titanium catalyst yields the regioregular, stereoregular poly[N-(1-anthryl)-N′-n-octadecylguanidine] (poly-1). A reversible thermo- and solvent-driven switching phenomena is exhibited by poly-1 (see scheme) in electronic circular dichroism and optical rotation studies. Furthermore, the helicity of poly-1 is assigned and the mechanism of this switching process is elucidated. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2005/z501977_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.}, number={44}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Tang, HZ and Novak, BM and He, JT and Polavarapu, PL}, year={2005}, pages={7298–7301} }
 @article{tang_boyle_novak_2005, title={Chiroptical switching polyguanidine synthesized by helix-sense-selective polymerization using [(R)-3,3 '-dibromo-2,2 '-binaphthoxy](di-tert-butoxy)titanium(IV) catalyst}, volume={127}, ISSN={["1520-5126"]}, DOI={10.1021/ja0453533}, abstractNote={A series of chiral binaphthyl titanium alkoxide complexes were synthesized. Among them, chiral titanium complex [(R)-3,3'-dibromo-2,2'-binaphthoxy](di-tert-butoxy)titanium(IV) (R-3) exists as a crystallographic C2 dimer in the solid state but a monomer in solution at room temperature. Application of R-3 in the helix-sense-selective polymerization of achiral carbodiimide, N-(1-anthryl)-N'-octadecylcarbodiimide (1), yielded a well-defined regioregular, stereoregular poly[N-(1-anthryl)-N'-octadecylguanidine] (poly-1b) with a relatively narrow polymer dispersity index of 2.7. Full racemization of poly-1b at +80 degrees C in toluene requires more than 100 h. Interestingly, poly-1b was found to undergo fast reversible chiroptical switching at +38.5 degrees C in toluene. Furthermore, at room temperature, poly-1b shows a positively signed Cotton effect in toluene, but negative ones in THF and chloroform, respectively. The chiroptical switching takes place around the toluene content of 90% (vol) in the mixed toluene/THF solvents. This is the first example of chiroptical switching phenomenon occurring in a helical polymer possessing no chiral moieties in the polymer chains. We believe this reversible chiroptical switching phenomenon occurs by reorientation of anthracene rings relative to the chain director.}, number={7}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Tang, HZ and Boyle, PD and Novak, BM}, year={2005}, month={Feb}, pages={2136–2142} }
 @article{goury_jhurry_bhaw-luximon_novak_belleney_2005, title={Synthesis and characterization of random and block copolypeptides derived from gamma-methylglutamate and leucine N-carboxyanhydrides}, volume={6}, ISSN={["1526-4602"]}, DOI={10.1021/bm049219m}, abstractNote={The synthesis of random and block copolypolyeptides derived from gamma-methylglutamate and leucine N-carboxyanhydrides using Al-Schiff's base complexes and allylamine as initiators is here reported. The copolymer structures were confirmed by (1)H and (13)C NMR. The calculation of the statistical average block lengths reveals the presence of longer methylglutamate units in the copolymer. The determination of the reactivity ratios indicated a slightly higher reactivity of gamma-methylglutamateNCA as compared to leucineNCA. Block copolypeptides containing glutamate and leucine units were obtained by sequential polymerization of the two NCAs using Al-Schiff's base complexes or allylamine in dioxane as solvent. Based on (13)C NMR spectra of copolymers exhibiting two signals corresponding to peptide linkages, we confirmed the block structure and concluded that the copolymerization proceeds by attack of an amino group present on a glutamate chain end onto a LeuNCA. The copolymerization with allylamine was also shown, from calculation of the average block lengths of sequences, to exhibit living behavior. Viscometry analysis further showed that molar masses of the copolypeptides obtained with Al-Schiff's base were quite close to those derived from allylamine, supporting the proposed mechanism of copolymerization.}, number={4}, journal={BIOMACROMOLECULES}, author={Goury, V and Jhurry, D and Bhaw-Luximon, A and Novak, BM and Belleney, J}, year={2005}, pages={1987–1991} }
 @article{kwark_novak_2004, title={Determination of the kinetic parameters of atom transfer radical polymerizations}, volume={37}, ISSN={["1520-5835"]}, DOI={10.1021/ma049627i}, abstractNote={In an attempt to find a novel catalyst system for atom transfer radical polymerization (ATRP), a parameter estimation method based on nonlinear regression was developed to evaluate various catalyst systems by determining kinetic parameters of polymerization. From our model system considering small molecular atom transfer addition reaction, we found that equilibrium constant of atom transfer reaction could be successfully determined using our parameter estimation method. However, the each value of activation rate constant and deactivation reaction constant is hard to be determined ubiquitously because of the poor sensitivities of them and the local minima trapping. By applying second minimization algorithm, the parameter estimation algorithm achieves higher propensity to reach global minimum, yet not all the time. The simulation results using kinetic rate constants determined by our method shows better agreement with the experimental data than that using literature values. This is because the current method uses fewer assumptions than other literature methods in determining rate constants. We also demonstrated the determination of kinetic constants in the polymerization of styrene and MMA using various metal catalysts, and the simulations using these kinetic constants agree well with the experimental data.}, number={25}, journal={MACROMOLECULES}, author={Kwark, YJ and Novak, BM}, year={2004}, month={Dec}, pages={9395–9401} }
 @article{nodono_novak_boyle_2004, title={Ethylene polymerization catalyzed by neutral nickel(II) complex with ON-chelating ligand}, volume={36}, ISSN={["0032-3896"]}, DOI={10.1295/polymj.36.140}, abstractNote={We have achieved the synthesis of neutral nickel catalyst with the modified O^N-chelating ligand for the ethylene polymerization. The activity of the catalyst, and the molecular weight and the branching structure of the polymer obtained strongly depend on the ligand structure as well as the presence of Ni(COD)2 which is used as an activator. The crystal structure of the catalyst was determined and the long nickel–phosphine bond length seems to play an important role for increasing the polymerization activity.}, number={2}, journal={POLYMER JOURNAL}, author={Nodono, M and Novak, BM and Boyle, PT}, year={2004}, pages={140–145} }
 @article{tian_lu_novak_2004, title={Helix-sense selective polymerization of carbodiimides: Building permanently optically active polymers from achiral monomers}, volume={126}, ISSN={["1520-5126"]}, DOI={10.1021/ja049548m}, abstractNote={The helix-sense selective polymerization of achiral monomers by homochiral catalysts was investigated. Polymerization of chiral carbodiimides (N-(R)-2,6-(dimethylheptyl)-N'-phenylcarbodiimide) by achiral catalysts yields polymers that undergo mutorotation at elevated temperatures, thus illustrating that these chains are formed under kinetic rather than thermodynamic control. Building on this observation, the polymerization of achiral carbodiimides by (S-BINOL)Ti(OiPr)2, I, was studied. Monomers (N-hexyl-N'-(X)carbodiimide, where X = isopropyl (3), hexyl (4) or phenyl (5)), N-methyl-N'-(2-methyl-6-isopropylphenyl)carbodiimide, 6, and N-dodecyl-N'-(1-naphthyl)carbodiimide, 7, were all polymerized with I in good yields (86-95%), and all showed varying degrees of asymmetric induction. Poly-3, -4, and -5 racemized upon heating at elevated temperatures, but poly-6 and poly-7, bearing nonsymmetric phenyl groups, yielded optically active polymers that could not be racemized even at elevated temperatures. Thin films of poly-7 were found to be highly opalescent.}, number={13}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Tian, GL and Lu, YJ and Novak, BM}, year={2004}, month={Apr}, pages={4082–4083} }
 @article{kim_novak_waddon_2004, title={Liquid crystalline properties of polyguanidines}, volume={37}, ISSN={["1520-5835"]}, DOI={10.1021/ma0493527}, abstractNote={Modified polyguanidines were prepared, and their liquid crystalline properties were studied using optical polarizing microscopy and X-ray diffraction. Parameters examined include chirality, the uniformity of the lengths of side chains, and attached side-chain mesogens. If the side chains on the repeat units are identical, then polymer has a more ordered structure in both solution and the solid state. Uniform lengths of the side chains are also important. Poly(N,N'-di-n-hexylguanidine), poly-I, exhibited a lyotropic smectic texture in contrast to a nematic texture of poly(N-(rac)-2-phenylethyl)-N'- methylguanidine) (poly-(rac-II)). Optically pure poly(N-((R)-2-phenylethyl)-N'-methylguanidine) (poly- (R-II)) formed a cholesteric texture, whereas the corresponding racemic polyguanidine, poly-(rac-II), formed a nematic texture. Additionally, poly-(R-II) displayed a mesophase at a lower critical concentration than either poly-I or poly-(rac-II), implying that poly-(R-II) is stiffer than these two other derivatives. Poly(N-6-((4'-methoxyphenylazo)phenyl-4-oxy)hexyl-N'-n-hexylguanidine) (poly-IV), one of combined liquid crystalline structures (liquid crystalline backbone plus liquid crystalline side chains), displayed a lyotropic nematic texture presumably due to the strong dipolar-dipolar interaction between the main chain and side chains that folds the appendages parallel to the molecular axis. Poly(N-12-((4'-methoxybiphenyl-4- oxy)dodecyl-N'-n-dodecylguanidine) (poly-V) and poly(N,N'-di-n-dodecylguanidine) (poly-VI) exhibited thermotropic liquid crystalline behavior.}, number={22}, journal={MACROMOLECULES}, author={Kim, J and Novak, BM and Waddon, AJ}, year={2004}, month={Nov}, pages={8286–8292} }
 @article{kim_novak_waddon_2004, title={Lyotropic liquid crystalline properties of poly(N,N '-di-n-hexylguanidine)}, volume={37}, ISSN={["1520-5835"]}, DOI={10.1021/ma035135e}, abstractNote={Stiff-chain polymers are of interest because of their unusual properties. An important subset of this class is the helical macromolecules, which encompass both natural1 (e.g., R-helical polypeptides, cellulosics, and the polynucleic acids) and synthetic polymers (e.g., polyisocyanates,2 polyisocyanides,3 and poly(cis-acetylenes)4). Not only is the intrachain conformation of the stiff helical polymers important, but also is their interchain ordering and packing. The importance of the latter manifests itself in their liquid crystalline behaviors1b and has ramifications in the design of supramolecular hierarchical structures. Within the synthetic helical systems, the lyotropic liquid crystalline properties of poly(n-hexyl isocyanate) have been studied in detail.5 Generally, and like many other stiff-chain polymers, poly(n-hexyl isocyanate) is known to display lyotropic nematic mesophases. Recently, in our group, the synthesis of a new class of related helical polymers, the polycarbodiimides (or polyguanidines), has been developed through a living route using a number of organometallic complexes as catalysts.6 Like the polyisocyanates, the rigidity of the polyguanidine backbone results from the combination of the coplanarity of the guanidinyl repeat units and the steric hindrance of adjacent side chains.2,7,8 By way of comparison, the polyguanidines possess two side chains per repeat while the polyisocyanates possess just one. One of our goals in synthesizing the polyguanidines was to increase their chain stiffness and helix inversion barriers, vis-à-vis the polyisocyanates, by increasing the intramolecular steric interactions through these added side chains. This also gives us an opportunity to explore how the side chain density influences the intermolecular solution and solid-state structures of these polymers. To this end, the lyotropic liquid crystalline properties of poly(N,N′-di-n-hexylguanidine), poly-I, were investigated using small-angle X-ray diffraction and optical polarizing microscopy.}, number={4}, journal={MACROMOLECULES}, author={Kim, J and Novak, BM and Waddon, AJ}, year={2004}, month={Feb}, pages={1660–1662} }
 @article{charvet_novak_2004, title={One-pot, one-catalyst synthesis of graft copolymers by controlled ROMP and ATRP polymerizations}, volume={37}, ISSN={["1520-5835"]}, DOI={10.1021/ma049244k}, abstractNote={Because of tremendous progress made in the development of living and stereoselective polymerization processes,1 complex polymeric molecules with well-defined architectures2 can now be readily prepared. This provides avenues to obtaining precise structure-property relationships and engineer materials with new and controllable properties. Of the various architectures known, graft copolymers are attractive materials for a wide range of applications3 due to their numerous structural variables that can be modified. A common route to well-defined graft copolymers relies on macromonomer polymerization that initially requires the preparation of a well-defined polymeric chain functionalized at one end by a polymerizable monomer.4 To simplify the overall preparation procedure, a one-step approach would be desirable. Here we report the first example of a one-pot synthesis of graft copolymers based on a metathesis skeleton with poly(methyl methacrylate) (PMMA) grafts using a single catalyst.}, number={23}, journal={MACROMOLECULES}, author={Charvet, R and Novak, BM}, year={2004}, month={Nov}, pages={8808–8811} }
 @article{tang_lu_tian_capracotta_novak_2004, title={Stable helical polyguanidines: Poly{N-(1-anthryl)-N '-[(R)- and/or (S)-3,7-dimethyloctyl]guanidines}}, volume={126}, ISSN={["1520-5126"]}, DOI={10.1021/ja049937g}, abstractNote={Using chiral catalysts of (R)- and/or (S)-BINOL-Ti, the asymmetrical polymerization of achiral monomer, N-(1-anthryl)-N'-n-octadecylcarbodiimide, yielded soluble nonregioregular polyguanidines of Poly-R1 and Poly-S1. A racemization process occurred when the toluene solution of Poly-R1 was annealed at elevated temperatures (70-80 degrees C). Kinetic studies reveal this to be a slow process with an activation energy of ca. 36 kcal/mol. On the other hand, using titanium(IV) trifluoroethoxide catalyst, the polymerization of N-(1-anthryl)-N'-[(R)- and/or (S)-3,7-dimethyloctyl]carbodiimides afforded highly regioregular polyguanidines of Poly-R2 and Poly-S2. These polymers adopt stable helices in various solvents and elevated temperatures, whose kinetically controlled conformations and thermodynamically controlled conformations are essentially the same.}, number={12}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Tang, HZ and Lu, YJ and Tian, GL and Capracotta, MD and Novak, BM}, year={2004}, month={Mar}, pages={3722–3723} }
 @misc{novak_tanaka_2003, title={Method for producing a polymer by coordination polymerization}, volume={6,579,956}, number={2003 June 17}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Novak, B. and Tanaka, H.}, year={2003} }
 @article{tian_boyle_novak_2002, title={Synthesis and crystal structure of a dinuclear palladium complex containing C,O-bridging ester-enolato moieties}, volume={21}, ISSN={["1520-6041"]}, DOI={10.1021/om010968j}, abstractNote={Palladium ester enolates have been prepared and characterized using IR, NMR, and single-crystal X-ray diffraction techniques. The X-ray diffraction established a dimeric crystal structure for complex {[N∧N]PdCH2C(O)OCH3}2 (N∧N = 1-[1-(5-methylpyrrole-2-yl)ethylidne]amino-2,6-diisopropylbenzene), 2, which contains C,O-bridging enolato groups. Upon reaction with donor molecules (acetonitrile, phosphines), the dimeric 2 cleaves to form monometallic C-bound enolate complexes, 3‘ and 4.}, number={7}, journal={ORGANOMETALLICS}, author={Tian, GL and Boyle, PD and Novak, BM}, year={2002}, month={Apr}, pages={1462–1465} }
 @article{lim_novak_2001, title={Helix conformation in helical polycarbodiimides studied by solid state C-13 NMR}, volume={272}, ISSN={["0301-0104"]}, DOI={10.1016/S0301-0104(01)00476-1}, abstractNote={Abstract The helix conformation in helical polycarbodiimides as a function of the side chains were studied by 13 C CP/MAS NMR. From these results, the structures of the all polycarbodiimides were defined, and the 13 C spin–lattice relaxation times in the rotating frame were measured. We discuss the mobility, the correlation time, and the activation energy for each carbon of the polycarbodiimides as a function of the side chains. The activation energies of main-chain carbons are strongly dependent on the side chains. From these results, the activation energies of the main-chain carbons for polycarbodiimides with directly bonded aromatic rings are distinctly different from those for polycarbodiimides with non-bonded aromatic rings. Based on our findings, we know that the polycarbodiimides with directly bonded aromatic rings have high activation energy and high helix reversal barriers.}, number={2-3}, journal={CHEMICAL PHYSICS}, author={Lim, AR and Novak, BM}, year={2001}, month={Oct}, pages={199–212} }
 @article{novak_cafmeyer_2001, title={Meta-stable enamines: Synthesis of simple enamines via catalytic isomerization of allylic amine substrates and their polymerization behavior}, volume={123}, DOI={10.1021/jo011609i}, number={44}, journal={Journal of the American Chemical Society}, author={Novak, B. M. and Cafmeyer, J. T.}, year={2001}, pages={11083–11084} }
 @article{tian_boone_novak_2001, title={Neutral palladium complexes as catalysts for olefin-methyl acrylate copolymerization: A cautionary tale}, volume={34}, ISSN={["0024-9297"]}, DOI={10.1021/ma010857w}, abstractNote={Neutral palladium complexes bearing pyrrole−imine ligands (I−III) have been synthesized, and their use as catalysts for olefin and vinyl monomer (co)polymerizations was investigated. Methyl acrylate (MA) has been homopolymerized in excellent yields (>95%) using these complexes. Copolymerizations of MA with norbornene or 1-hexene in the presence of these catalysts produce acrylate-enriched copolymers. Hypothesizing that metal enolates are potential intermediates in some of these polymerizations, palladium enolate complexes (IV−VII) containing ligand 1 were tested for their catalytic activity. Surprisingly, these complexes proved inactive toward acrylate and/or olefin polymerizations. Further mechanistic studies have shown that the homo- and copolymers obtained using these complexes arise from a radical mechanism rather than the anticipated metal-mediated process.}, number={22}, journal={MACROMOLECULES}, author={Tian, GL and Boone, HW and Novak, BM}, year={2001}, month={Oct}, pages={7656–7663} }
 @article{charvet_novak_2001, title={New functional monomers for well-controlled ROMP polymerizations}, volume={34}, ISSN={["0024-9297"]}, DOI={10.1021/ma0109875}, abstractNote={The ring-opening metathesis polymerization of cyclobutene-containing monomers based on the endo-tricyclo[4.2.2.02,5]deca-3,9-diene structure bearing cyclic anhydride and N-alkyl- or N-phenyl-substituted succinimides at the 7- and 8-positions was investigated. Well-defined molybdenum and ruthenium complexes were used as catalysts. Cl2Ru(CHPh)(PCy3)2 (III) was shown to be the most suitable catalyst as a well-controlled and even living polymerization was observed. Mainly cis stereochemistry (≈75%) was observed in the main chain. Kinetic studies with different substituted succinimide moieties indicated that the polymerization rate depended on electronic effects in the monomer. 19F NMR of fluorinated polymers suggests that through-space interactions between fluorine groups and the main polymer chain occur. These new polymers have a good thermal stability (304 °C < Td < 344 °C). Upon hydrogenation, the N-methylsuccinimide functionalized polymer exhibited a Tg at 285 °C, and the thermal stability increased by ab...}, number={22}, journal={MACROMOLECULES}, author={Charvet, R and Novak, BM}, year={2001}, month={Oct}, pages={7680–7685} }
 @article{aoyama_novak_2001, title={Pyridine rings as protected 2(circle) amines: Facile hydrogenation of heterocyclic aromatic polymers}, volume={34}, ISSN={["1520-5835"]}, DOI={10.1021/ma011013f}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTPyridine Rings as Protected 2° Amines: Facile Hydrogenation of Heterocyclic Aromatic PolymersYoko Aoyama and Bruce M. NovakView Author Information Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, and Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695 Cite this: Macromolecules 2001, 34, 20, 6842–6844Publication Date (Web):August 18, 2001Publication History Received11 June 2001Published online18 August 2001Published inissue 1 September 2001https://doi.org/10.1021/ma011013fCopyright © 2001 American Chemical SocietyRequest reuse permissionsArticle Views384Altmetric-Citations5LEARN 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 (49 KB) Get e-AlertscloseSUBJECTS:Amines,Catalysts,Hydrogenation,Polymers,Pyridines Get e-Alerts}, number={20}, journal={MACROMOLECULES}, author={Aoyama, Y and Novak, BM}, year={2001}, month={Sep}, pages={6842–6844} }
 @article{goodson_novak_2001, title={Synthesis and characterization of wormlike three-arm poly(n-hexyl isocyanate) star polymers}, volume={34}, ISSN={["0024-9297"]}, DOI={10.1021/ma991692i}, abstractNote={We have previously reported the use of titanium alkoxide complexes as initiators for the living polymerization of isocyanates. In this paper, we present the synthesis of a trimetallic initiator, 2, comprised of three titanium alkoxides connected to a central organic core and the use of this catalyst to form three-arm star polymers which contain rigid polyisocyanate arms. Kinetic and molecular weight experiments confirm that the trimetallic complex 2, like its monometallic analogue, 6, initiates the living polymerization of n-hexyl isocyanate and that the three-arm stars obtained from 2 are completely symmetrical. The number-average molecular weight of polymer obtained from 2 increases linearly with the monomer-to-catalyst ratio used, which indicates a lack of chain transfer during polymerization. A comparison of the rates of polymerization of n-hexyl isocyanate by 2 and 6 at fixed initial monomer and titanium concentrations (k 2 = (3.99 ± 0.2) x 10 -3 M min -1 , k 6 = (3.84 ± 0.1) x 10 -3 M min -1 ) demonstrates that all three titanium centers in 2 are active and propagate independently of one another. The solution properties of these new three-arm star polymers were examined through tandem GPC/light scattering and solution viscometry experiments. Light scattering shows that there is a 55% reduction in the mean-square radius of gyration (g = star / linear = 0.45 ± 0.05) of the three-arm star polyisocyanate from that of a linear polyisocyanate of the same molecular weight. The experimental value of g approaches the rod limit of g that indicates that the arms of the three-arm star can be construed as stiff, wormlike chains. Additionally, there is a 28% reduction in the intrinsic viscosity of three-arm polyisocyanate star from that of its linear equivalent. Finally, a 30% w/w solution of three-arm star polyisocyanate displays a nematic, lyotropic liquid crystalline mesophase.}, number={12}, journal={MACROMOLECULES}, author={Goodson, SH and Novak, BM}, year={2001}, month={Jun}, pages={3849–3855} }
 @article{lim_chang_kim_novak_2000, title={Carbon-13 T-1 rho investigation in two polycarbodiimides}, volume={115}, ISSN={["0038-1098"]}, DOI={10.1016/S0038-1098(00)00129-0}, abstractNote={The molecular motions of carbons in two polycarbodiimides were studied by 13C cross-polarization, magic angle spinning nuclear magnetic resonance. From these results, the 13C spin-lattice relaxation times in the rotating frame were measured. In this paper we discuss the molecular motions for each carbon of the two polycarbodiimides. The main-chain carbon of polycarbodiimide (I) with methyl has higher activation energy, 23.12 kJ/mol, than that of polycarbodiimide (II) with the methoxy side chain, 10.47 kJ/mol. From these results, we surmise that polycarbodiimide (I) has a bigger steric interaction with the main-chain carbon since the methyl group is located in the meta-position of the aromatic ring.}, number={1}, journal={SOLID STATE COMMUNICATIONS}, author={Lim, AR and Chang, JH and Kim, JH and Novak, BM}, year={2000}, pages={23–28} }
 @misc{boffa_novak_2000, title={Copolymerization of polar monomers with olefins using transition-metal complexes}, volume={100}, ISSN={["1520-6890"]}, DOI={10.1021/cr990251u}, abstractNote={Transition-metal catalysts long ago made it from the laboratory bench to the polymerization reactor. Indeed, they are being used around the world to make more than 70 million tons of polyethylene and polypropylene a year. Transition-metal catalysts give polyolefin producers unprecedented flexibility in process and polymer design. However, there are still new worlds for catalysts to conquer. One of the most challenging targets is the controlled copolymerization of simple olefins with polar functional monomers. Success in this area would mark a quantum advance in polyolefin field.}, number={4}, journal={CHEMICAL REVIEWS}, author={Boffa, LS and Novak, BM}, year={2000}, month={Apr}, pages={1479–1493} }
 @article{lim_kim_novak_2000, title={Solid state C-13 nuclear magnetic resonance for polyguanidines}, volume={41}, ISSN={["0032-3861"]}, DOI={10.1016/S0032-3861(99)00431-0}, abstractNote={The structure and variations in dynamic motions of three polyguanidines possessing different side chains were studied by 13C CP/MAS NMR. From these results, the structures of the polyguanidines were confirmed, and the 13C spin–lattice relaxation times in the rotating frame were measured. The polyguanidine backbone mobilities were measured as a function of size and chemical make up (aliphatic vs. aromatic). The main-chain carbon of polyguanidine (II) with aromatic side chains has a higher activation energy, 23.12 kJ/mol, than the polyguanidine (I) with aliphatic side chains, 19.76 kJ/mol. Also, the activation energy of the main-chain carbons of polyguanidine (II) and (III) with aromatic side chains was found to depend on the size of side chains.}, number={7}, journal={POLYMER}, author={Lim, AR and Kim, JH and Novak, BM}, year={2000}, month={Mar}, pages={2431–2438} }
 @article{jin_novak_2000, title={Synthesis of beta-iminoaminate zirconium complexes and their application in ethylene polymerization}, volume={33}, ISSN={["1520-5835"]}, DOI={10.1021/ma0000428}, abstractNote={ADVERTISEMENT RETURN TO ISSUECommunication to the...Communication to the EditorNEXTSynthesis of β-Iminoaminate Zirconium Complexes and Their Application in Ethylene PolymerizationXin Jin and Bruce M. NovakView Author Information Polymer Science and Engineering Department, University of Massachusetts, Amherst, Massachusetts 01003, and Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695 Cite this: Macromolecules 2000, 33, 17, 6205–6207Publication Date (Web):August 3, 2000Publication History Received11 January 2000Revised11 July 2000Published online3 August 2000Published inissue 1 August 2000https://doi.org/10.1021/ma0000428Copyright © 2000 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views369Altmetric-Citations32LEARN 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 (60 KB) Get e-AlertsSUBJECTS:Aromatic compounds,Catalysts,Hydrocarbons,Ligands,Polymerization Get e-Alerts}, number={17}, journal={MACROMOLECULES}, author={Jin, X and Novak, BM}, year={2000}, month={Aug}, pages={6205–6207} }
 @article{lim_novak_1999, title={C-13 NMR study on helix inversion barrier in polyguanidines}, volume={112}, ISSN={["0038-1098"]}, DOI={10.1016/s0038-1098(99)00324-5}, abstractNote={The activation energy of the main-chain carbons for copolymerization of both enantiomers in polyguanidines has been studied using measurements of 13C T1ρ relaxation times. The activation energies of main-chain carbons depend on the ratios for copolymerization of both enantiomers. The activation energies of the carbons in three polyguanidines are distinctly different from those in pure [R] and [S] polyguanidines previously reported. It is worth noting that the carbon of 24.6% EE has a larger activation energy than 48.8 and 81.7%EE polymers. This large activation energy means that the backbone mobility is hindered; we think that this prevents a smooth precession of the chain around the helix axis.}, number={8}, journal={SOLID STATE COMMUNICATIONS}, author={Lim, AR and Novak, BM}, year={1999}, pages={459–464} }
 @article{schueneman_lesser_hobbs_novak_1999, title={Evaluation of short term-high intensity thermal degradation of graphite fiber reinforced laminates via ultrasonic spectroscopy}, volume={37}, ISSN={["1099-0488"]}, DOI={10.1002/(SICI)1099-0488(19990915)37:18<2601::AID-POLB5>3.0.CO;2-Z}, abstractNote={In certain fire situations, a structural or load-bearing polymer matrix composite (PMC) may be exposed to excessive thermal loads that degrade the matrix. In this paper, we report the results of a study to assess the utility of ultrasonic spectroscopy as a means of assessing the residual physical and mechanical characteristics of PMCs exposed to excessive thermal loads. We show that the measured power spectra of ultrasonic energy correlates with performance of graphite fiber epoxy matrix composites exposed to thermal degradation. Unidirectional composites were exposed to short term-high intensity thermal loads at one end of the specimen. Thus, inducing a thermal gradient along the length of the specimen. Simultaneous thermogravimetric analysis - differential scanning calorimetry (TGA/DSC) and Fourier transform infrared spectroscopy (FTIR) analysis of the aged specimens revealed a gradient in thermal degradation. The thermal loads induced substantial degradation of the composite. However, the amplitude of the power spectra is observed to increase gradually then sharply prior to its complete attenuation due to delaminations. Mode I fracture toughness tests correlate with the observed changes in the ultrasonic spectra. FTIR, TGA/ DSC, fracture toughness, and ultrasonic spectral analysis all indicate the same critical temperature at which thermally induced damage sharply increased.}, number={18}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Schueneman, GT and Lesser, AJ and Hobbs, TR and Novak, BM}, year={1999}, month={Sep}, pages={2601–2610} }
 @article{lim_kim_novak_1999, title={Rigidity of the backbone for poly(bis(4-butoxycarbonylphenyl))carbodiimide and poly(bis(4-butylphenyl))carbodiimide studied by solid state C-13 T-1p measurements}, volume={246}, ISSN={["0301-0104"]}, DOI={10.1016/S0301-0104(99)00126-3}, abstractNote={Abstract The structure and rigidity of the backbone of two polycarbodiimides as a function of the side chains were studied by 13 C CP/MAS NMR. From these results, the structures of the polycarbodiimides were determined, and the 13 C spin–lattice relaxation times in the rotating frame were measured. Based on our findings, we discuss the mobility for the backbone of the two polycarbodiimides with and without ester linkage between the aromatic and aliphatic side chains. The backbone carbon of polycarbodiimide I with ester linkage has a lower activation energy, 18.63 kJ/mol, than the polycarbodiimide II without ester linkage, 23.20 kJ/mol. Also, the activation energies of the aliphatic side chains show gradually increasing values. We think that this increase results from the greater mobility of the alkyl chain toward its free end.}, number={1-3}, journal={CHEMICAL PHYSICS}, author={Lim, AR and Kim, JH and Novak, BM}, year={1999}, month={Jul}, pages={373–380} }
 @article{lim_schueneman_novak_1999, title={Solid state NMR of SiO2 nanotube coated ammonium tartrate crystal}, volume={110}, ISSN={["0038-1098"]}, DOI={10.1016/S0038-1098(99)00046-0}, abstractNote={Ammonium tartrate crystal and SiO2 nanotube coated ammonium tartrate crystal were studied by 13C CP/MAS NMR, and the structure of two samples were verified using the 13C NMR spectrum. The spin–lattice relaxation times for the carbons in the rotating frame, T1ρ, have been measured as a function of temperature. All relaxation times of the carbons in the two materials undergo slow motions, i.e. motions on the slow side of the T1ρ minimum. From these relaxation times, we determine the activation energy for the ammonium tartrate crystal and SiO2 nanotube coated ammonium tartrate crystal, respectively. The activation energies for the SiO2 nanotube coated ammonium tartrate crystal were found to be generally higher than those of ammonium tartrate crystal. We think that the higher activation energy for the hydrocarbon in the SiO2 nanotube coated ammonium tartrate crystal is because of the bonding between the oxygen in the SiO2 nanotube and the hydroxyl group of the ammonium tartrate crystal.}, number={6}, journal={SOLID STATE COMMUNICATIONS}, author={Lim, AR and Schueneman, GT and Novak, BM}, year={1999}, pages={333–338} }
 @article{lim_novak_1999, title={The C-13 spin-lattice relaxation time for poly (di-N-hexyl)}, volume={109}, number={1}, journal={Solid State Communications}, author={Lim, A. R. and Novak, B. M.}, year={1999}, pages={29–34} }
 @article{lim_stewart_novak_1999, title={The T-1 rho C-13 spin-lattice relaxation time of helical polyguanidines}, volume={110}, ISSN={["0038-1098"]}, DOI={10.1016/S0038-1098(99)00038-1}, abstractNote={The solid state dynamics of three helical polyguanidines differing only in their stereochemistry was investigated by 13C CP/MAS NMR. From these studies, the structures of the polyguanidines were confirmed, and the 13C spin–lattice relaxation times in the rotating frame were measured. The relaxation times of all the polyguanidines indicated that they undergo fast motions, i.e. motions on the fast side of the T1ρ minimum. The main chain carbon of polyguanidine I-(R/S), with equal amounts of (R) and (S) chiral side chains, has higher activation energy, 10.7 kJ/mol, than the analogous polymers with enantiomerically pure side chains (I-(R) and I-(S)), 5.1 kJ/mol.}, number={1}, journal={SOLID STATE COMMUNICATIONS}, author={Lim, AR and Stewart, JR and Novak, BM}, year={1999}, pages={23–28} }
 @article{lim_schueneman_novak_1999, title={The T-l rho C-13 spin-lattice relaxation time of interpenetrating networks by solid state NMR}, volume={109}, ISSN={["0038-1098"]}, DOI={10.1016/S0038-1098(98)00576-6}, abstractNote={Poly (2-hydroxyethyl methacrylate) (PHEMA) and poly(2-hydroxyethyl methacrylate) interpenetrated with 5% SiO2 (PHEMA-IPN) were studied by 13C CP/MAS NMR. From these results, the structure of two polymers were verified by 13C NMR. Spin-lattice relaxation times for the polymer carbons in the rotating frame, T1ρ, have been measured as a function of temperature. The T1ρ spin-lattice relaxation times of the α-quarternary and carbonyl in the PHEMA and PHEMA-IPN undergo slow motions, i.e., motions on the slow side of the T1ρ minimum, while those of the 1-,2-, β-methylene, and 3-methyl undergo fast motions, i.e., motions on the fast side of the T1ρ minimum. From these T1ρ spin-lattice relaxation times, we discuss the mobility, the correlation time, and activation energy for the PHEMA and PHEMA-IPN, respectively. The activation energies for the PHEMA-IPN were found to be generally higher than those of PHEMA. The higher activation energy for the side-chain 2-methylene in the PHEMA-IPN is attributed to bonding between the SiO2 and the hydroxyl group of the PHEMA.}, number={7}, journal={SOLID STATE COMMUNICATIONS}, author={Lim, AR and Schueneman, GT and Novak, BM}, year={1999}, pages={465–470} }