Experimental Determination of Sequence Length Distribution of Hard Segments in Polyester-Polyurethanes

Abstract

A new analytical procedure based on selective acid hydrolysis was developed to measure the chain length distribution of hard segmenta (HSCLD) of polyester-polyurethanes. It was tested with polymers made from 4,4'-methylenebis(phenyl isocyanate), 1,6-hexanediol, and α,ω-dihydroxypoly(hexamethylene adipate) with molecular weight M n 2200. Heating samples with 0.25 M HCl solution in DMSO with 8.2% water for 36 h leads to nearly complete hydrolysis of the ester groups, leaving the urethanes largely unaffected. The resulting mixture of oligomers can be analyzed by SEC, using DMF at room temperature as the solvent. Experimentally measured HSCLDs were most often very different from those theoretically predicted for homogeneous reaction