Solid-state C-13 and Xe-129 NMR study of poly(vinyl alcohol) and poly(vinyl alcohol)/lactosilated chitosan gels

Dry and hydrated poly(vinyl alcohol) (PVA) gels with 55% (a-PVA) and 61% (s-PVA) syndiotacticity and related PVA/lactyl chitosan (LC) blends have been investigated with Xe-129 and cross-polarization/magic-angle-spinning C-13 NMR techniques. Although the dry gels exhibit two broad Xe-129 resonances in the slow-to-intermediate exchange limit, both hydrated gels show three resonances. The corresponding dry blends exhibit two signals, the chemical shifts and line widths of which change with respect to those of pure PVA, whereas one (a-PVA/LC) or two (s-PVA/LC) signals appear in the spectra of the hydrated blends. A comparative analysis of the data demonstrates that LC rearranges the domains of the polymeric matrix in both the dry and hydrated blends according to the syndiotacticity of the PVA chains. Information on the molecular motions of the amorphous and swollen polymeric domains in the kilohertz range has been obtained from an analysis of the spin-lattice relaxation times. These data indicate that the dynamics and arrangement of the PVA chains in the gels are strongly affected by their tacticity and the addition of the copolymer LC. (C) 2003 Wiley Periodicals, Inc.