Solid‐state ¹³C nuclear magnetic resonance characterization of MDI‐based polyurethanes

Abstract 13 C solid‐state nuclear magnetic resonance (NMR) experiments on linear polyurethanes and poly(ether‐urethane) block copolymers demonstrate that 13 C spin‐lattice relaxation experiments in the laboratory [ T 1 ( C )] and rotating [ T 1 p ( C )] frames provide the most information about domain morphology in these microphase‐separated polymer systems. T 1 ( H ) T CH , and T 1 p ( 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 T 1 ( C and T 1 p ( C ) times fall in characteristic ranges for crystalline, amorphous, interfacial, and dissolved species. BD methylene carbons have short T 1 p ( C ) for crystalline and long T 1 p ( C ) for amorphous hard‐segment aggregates. The distinct T 1 p ( C ) and T 1 ( C ) fractins observed are attributed to the presence of several crystalline polymorphs. Both T 1 ( 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.