Sequence distribution of segmented polyurethane-urea

Abstract

Segmented polyurethane-urea (SPU) elastomer was prepared from polytetramethyleneglycol (PTMG), 4,4′-diphenylmethane diisocyanate (MID), and ethylenediamine (EDA). The SPU is a kind of block copolymer composed of soft and hard segments. 13C NMR spectra of the SPU were measured and the mean sequence lengths of polyurethane block and polyurea block were estimated from the signals of aromatic carbons. The mean polyurea sequence length was shorter than the hard segment as estimated by X-ray diffraction (Kimura et al.) or by other methods (Suzuki et at.). This polymer was found to be almost a random copolymer. The reactivity of the isocyanate group in MDI decreases slightly when the other side of isocyanate has reacted. The hard segment observed by X-ray diffraction or by other methods might only be the longer fraction of polyurea sequences.