@article{kalachandra_lin_stejskal_prakki_offenbacher_2005, title={Drug release from cast films of ethylene vinyl acetate (EVA) copolymer: Stability of drugs by H-1 NMR and solid state C-13 CP/MAS NMR}, volume={16}, ISSN={["1573-4838"]}, DOI={10.1007/s10856-005-2529-1}, abstractNote={The study utilizes an oral biocompatible material based on ethylene vinyl acetate copolymer (EVA) designed to release drugs in vitro at therapeutic levels over several days. We examined the drug stability during film casting process using proton and solid state NMR techniques. The drug-loaded EVA films were prepared from the dry sheet obtained by solvent (dichloromethane) evaporation of polymer casting solutions. Drugs tested include chlorhexidine diacetate (CDA), doxycycline hydrochloride (DOH), tetracycline hydrochloride (TTH) and nystatin (NST). Drug release from the films was examined for at least 14 days in 10 ml ddH2O (NST in water/ethanol (4:1)) which was replaced daily. Changes in optical density were followed spectraphotometrically. Effect of temperature on rate measurements was studied and the energies of activation (E*) were calculated using Arrhenius plots. Effect of EVA copolymer composition on CDA release rate was also investigated. The enhanced rates with temperature increase may be attributed to the formation of channels with increased geometry in the polymer. The highest E* observed for CDA compared to DOH and TTH may be related to their average molecular weights. Spectral analyses for CDA and NST revealed that the chemical and physical structures of the drugs remained unaffected during the film casting process.}, number={7}, journal={JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE}, author={Kalachandra, S and Lin, DM and Stejskal, EO and Prakki, A and Offenbacher, S}, year={2005}, month={Jul}, pages={597–605} }
 @article{wachowicz_wolak_gracz_stejskal_jurga_mccord_white_2004, title={Length scales which perturb chain packing in amorphous polymers}, volume={37}, ISSN={["1520-5835"]}, DOI={10.1021/ma049263u}, abstractNote={Direct spectroscopic probes of individual chain conformation and free volume are used to measure the increasing perturbation in the local glass-transition temperature of one polymer chain with decreasing length scale of mixing in binary polyolefin blends. Solid-state 2H and 129Xe NMR experiments reveal a compositional miscibility window in side-chain concentration for polyisobutylene (PIB)/poly(ethylene-co-butene) (PEB) blends. A combination of pulsed-field gradient and chemical shift data for xenon gas absorbed in these polymer blends indicates that the presence of polymer chains within a radius of ∼35 nm of a different chain structure will perturb the intermolecular packing contribution to the total conformational energy of that chain, thereby changing its Tg.}, number={12}, journal={MACROMOLECULES}, author={Wachowicz, M and Wolak, J and Gracz, H and Stejskal, EO and Jurga, S and McCord, EF and White, JL}, year={2004}, month={Jun}, pages={4573–4579} }
 @article{wolak_jia_gracz_stejskal_white_wachowicz_jurga_2003, title={Polyolefin miscibility: Solid-state NMR investigation of phase behavior in saturated hydrocarbon blends}, volume={36}, ISSN={["0024-9297"]}, DOI={10.1021/ma0301449}, abstractNote={Chain-level mixing in polyolefins is investigated for blends of polyisobutylene (PIB) and polyethylene-co-1-butene (PEB). Previous reports suggest that PIB exhibits unusual mixing behavior in certain saturated blends relative to other polyolefins, even though it is immiscible with most. Variable-temperature 1H, 2H, 13C, and 129Xe NMR experiments are used to characterize local PIB chain dynamics in blends with PEB in which the concentration of 1-butene comonomer units is 23 or 66 wt %. Results from 1D and 2D solid-state 13C exchange experiments, 1H relaxation measurements, and 2H line shape analysis indicate that local conformational dynamics of the PIB CH2 group in the polymer backbone increase significantly in blends with PEB copolymers containing 66 wt % butene comonomer (PEB-66). Even though the PEB-66 is a higher Tg polymer than PIB, PIB exhibits a lower effective Tg when the blend is formed relative to its pure state. Similar perturbations are not observed in the PIB/PEB-23 blend, indicating that thi...}, number={13}, journal={MACROMOLECULES}, author={Wolak, J and Jia, X and Gracz, H and Stejskal, EO and White, JL and Wachowicz, M and Jurga, S}, year={2003}, month={Jul}, pages={4844–4850} }
 @article{merkel_toy_andrady_gracz_stejskal_2002, title={Investigation of Enhanced Free Volume in Nanosilica-Filled Poly(1-trimethylsilyl-1-propyne) by 129Xe NMR Spectroscopy}, volume={36}, ISSN={0024-9297 1520-5835}, url={http://dx.doi.org/10.1021/ma0256690}, DOI={10.1021/ma0256690}, abstractNote={The gas permeability of poly[1-(trimethylsilyl)-1-propyne] (PTMSP) containing nanoparticulate fumed silica increases with increasing filler content. This unusual phenomenon is explored using 129Xe NMR spectroscopy to examine the effect of filler on the free volume of the PTMSP host matrix. The 129Xe NMR chemical shift decreases regularly with increasing fumed silica concentration, consistent with an increase in the average size of free volume elements or cavities through which molecular transport can occur. A relationship between the chemical shift and gas permeability in the filled polymer is reported.}, number={2}, journal={Macromolecules}, publisher={American Chemical Society (ACS)}, author={Merkel, T. C. and Toy, L. G. and Andrady, A. L. and Gracz, H. and Stejskal, E. O.}, year={2002}, month={Dec}, pages={353–358} }
 @article{da silva_tavares_stejskal_2000, title={C-13-Detected H-1 spin diffusion and H-1 relaxation study of multicomponent polymer blends}, volume={33}, number={1}, journal={Macromolecules}, author={Da Silva, N. M. and Tavares, M. I. B. and Stejskal, E. O.}, year={2000}, pages={115–119} }
 @article{collins_kim_holton_sierzputowska-gracz_stejskal_2000, title={NMR quantum computation with indirectly coupled gates}, volume={62}, ISSN={1050-2947 1094-1622}, url={http://dx.doi.org/10.1103/PhysRevA.62.022304}, DOI={10.1103/physreva.62.022304}, abstractNote={An NMR realization of a two-qubit quantum gate which processes quantum information indirectly via couplings to a spectator qubit is presented in the context of the Deutsch-Jozsa algorithm. This enables a successful comprehensive NMR implementation of the Deutsch-Jozsa algorithm for functions with three argument bits and demonstrates a technique essential for multi-qubit quantum computation.}, number={2}, journal={Physical Review A}, publisher={American Physical Society (APS)}, author={Collins, David and Kim, K. W. and Holton, W. C. and Sierzputowska-Gracz, H. and Stejskal, E. O.}, year={2000}, month={Jul} }
 @article{morgan_stejskal_andrady_1999, title={129Xe NMR Investigation of the Free Volume in Dendritic and Cross-Linked Polymers}, volume={32}, ISSN={0024-9297 1520-5835}, url={http://dx.doi.org/10.1021/ma9813643}, DOI={10.1021/ma9813643}, abstractNote={129Xe NMR spectroscopy was used to study the free-volume changes associated with cross-linking of linear polymers and extensive chain branching in dendritic tree molecules. Qualitative changes in the free volume in model networks of poly(oxypropylene) and in starburst dendrimers of poly(amidoamine) were studied as a function of the cross-link density and the generation, respectively. Consistent with the present understanding of these end-linked networks, the change in chemical shift of the xenon was found to correlate well with the reciprocal of the average molecular weight between cross-links of the end-linked networks. With dendrimers, the chemical shift of xenon varied linearly with the generation number. A modified form of the chain-end free volume theory applicable to dendritic molecules was used to interpret the data.}, number={6}, journal={Macromolecules}, publisher={American Chemical Society (ACS)}, author={Morgan, D. R. and Stejskal, E. O. and Andrady, A. L.}, year={1999}, month={Mar}, pages={1897–1903} }
 @article{roberts_sierzputowska-gracz_stejskal_osteryoung_1998, title={Determination of Li+ self-diffusion coefficients in an aqueous suspension of sulfonated polystyrene latex by pulsed-field-gradient, spin-echo NMR}, volume={102}, number={40}, journal={Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces & Biophysical}, author={Roberts, J. M. and Sierzputowska-Gracz, H. and Stejskal, E. O. and Osteryoung, J. G.}, year={1998}, pages={7735–7739} }