Monday, January 07, 2008

Hiyam's Journal Update

Chem. Mater., 20 (1), 287–293 10.1021/cm071822z Web Release Date: December 6, 2007 Copyright © 2008 American Chemical Society
Nanoheterogeneity of a Polymer Blend and the Effect of Humidity as Characterized by Solid-State NMR
Stuart A. Brewer,*† David C. Apperley,‡ and Corinne A. Stone†

A material that potentially displays both breathability and chemical barrier properties has been the center of this study. This material is based on a hydrogel formed between polyvinyl alcohol, polyethyleneimine, and water. An important aspect of this study has been a need to obtain a greater understanding of the solid-state structure adopted by the material. Consequently, a detailed investigation of the polymer blend was conducted by solid-state NMR. A combination of high-resolution carbon-13 cross-polarization and fast-recycle direct-polarization experiments, together with 1H wide-line measurements, has yielded a wealth of information on the domain structure of the material and the characteristics of those domains. The effects of environmental humidity on the polymer blend have also been studied.

Chem. Mater., 20 (1), 294–302 10.1021/cm0716598 Web Release Date: December 5, 2007 Copyright © 2008 American Chemical Society
Solid-State NMR Study of the Role of H and Na in AB-Type Carbonate Hydroxylapatite
Harris E. Mason,*†‡ Andrew Kozlowski,†§ and Brian L. Phillips†‡

Solid-state nuclear magnetic resonance (NMR) techniques, combined with Fourier transform infrared (FT-IR) spectroscopy, were used to study synthetic AB-type carbonate hydroxylapatite (CHAp). 13C{1H} heteronuclear correlation (HetCor) experiments indicate that the two carbonate environments represented by the peaks at δC = 169.8 and 170.8 ppm are associated with three H environments with one environment represented by a peak centered about δH = 0.0 ppm and two additional peaks located at 1.3 and 5.5 ppm. The peaks near δH = 0.0 ppm correspond to hydroxyl environments within the channels of the CHAp, whereas those at 1.3 and 5.5 exhibit spectral characteristics consistent with bicarbonate ions that donate moderate to weak hydrogen bonds. Possible methods by which bicarbonate incorporation can be accommodated by the apatite structure are discussed. The Na/carbonate ratio and 23Na NMR spectroscopy indicate that Na plays an important role in the carbonate incorporation in these materials.

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