SOLID-STATE C-13 NUCLEAR-MAGNETIC-RESONANCE CHARACTERIZATION OF MDI-BASED POLYURETHANES

C-13 solid-state nuclear magnetic resonance (NMR) experiments on linear polyurethanes and poly(ether-urethane) block copolymers demonstrate that C-13 spin-lattice relaxation experiments in the laboratory [T1 (C)] and rotating [T1rho(C)] frames provide the most information about domain morphology in these microphase-separated polymer systems. T1 (H), T(CH), and T1rho(H) data are less useful. In a 4,4'-methylene bis (p-phenyl isocyanate) -1,4-butanediol (MDI/BD) hard-segment material, the MDI bridging methylene and the MDI urethane carbonyl T1 (C) and T1rho(C) times fall in characteristic ranges for crystalline, amorphous, interfacial, and dissolved species. BD methylene carbons have short T1rho(C) for crystalline and long T1rho(C) for amorphous hard-segment aggregates. The distinct T1rho(C) and T1(C) fractions observed are attributed to the presence of several crystalline polymorphs. Both T1(C) results and DSC endotherms indicate that the crystalline polymorphs present in the poly(ether-urethane) are less ordered than the types seen in the pure hard-segment material. (C) 1993 John Wiley & Sons, Inc.