Subglass and Glass Transitions of Poly(di-n-alkylitaconate)s with Various Side-Chain Lengths: Solid-State NMR Investigation

Variable-temperature high-resolution solid-state 13 C NMR experiments were performed on poly-(di-n-alkylitaconate)s in bulk. Temperature-dependent line broadenings resulting from either motional modulation of the 13 C- 1 H dipolar coupling or motional modulation of the chemical shift anisotropy were observed for each carbon atom of the polymer main chain and side chains. Similarly, independent determinations of the 13 C- 1 H dipolar couplings and 13 C chemical shift anisotropies demonstrated the existence of local motions in solid poly-(di-n-alkylitaconate)s. All of these measurements led to a direct identification of the moving units that are involved in the various relaxations, which were previously investigated by using dielectric relaxation experiments.