Molecular level structural heterogeneity in poly(ether-ester)/poly(vinyl chloride) blend characterized by cross-polarization magic angle spinning C-13 nuclear magnetic resonance spectroscopy

Abstract

A blend of poly(ether-ester) and poly(vinyl chloride) (PVC) was examined by dynamic mechanical analysis and cross-polarization/magic angle spinning (CP/MAS) C-13 NMR spectroscopy. The presence of structural heterogeneity in the solid blend was identified by the temperature dependence of its frequency-swept viscoelastic behavior. In the CP/MAS C-13 NMR experiment, analysis of the magnetization decay of specific carbons as a function of delay time determined the proton spin-lattice relaxation times in the laboratory frame, T-1, and the rotating frame, T-1 rho, for the two polymers in their respective pure states and in the 50/50 blend. This analysis provided more precise information pertaining to the microheterogeneity and the molecular state of mixing in the blend. The single-exponential decay of T-1 relaxation of the blend confirmed a homogeneity on a characteristic length of 26 nm estimated from the spin diffusion process. The double decompositions in the T-1 rho relaxation of component polymers in the blend indicated a coexistence of a mixed and two structurally heterogeneous phases which corresponded to poly(ether-ester) hard segments and PVC microcrystallites. The maximum size of the microheterogeneous phases was estimated to be ca. 24 Angstrom.