The effect of varying soft and hard segment length on the structure–property relationships of segmented polyurethanes based on a linear symmetric diisocyanate, 1,4-butanediol and PTMO soft segments

Abstract

Thermoplastic segmented polyurethanes which are based on poly(tetramethylene oxide) (PTMO) soft segment, linear symmetric para-phenylene diisocyanate (pPDI), and chain extended with 1,4-butanediol (BD) are discussed. The effect of variation of the soft and hard segment molecular weights as well as the overall hard segment content on structure-property behavior is investigated. Together, atomic force microscopy (AFM) and dynamic mechanical analysis (DMA) clearly establish the presence of a unique ordered thread-like microphase separated structure that displays considerable order. This thread-like microphase structure is similar to that of the "single molecule" hard segment systems reported earlier from our laboratory [1-4]. In addition, small angle X-ray scattering (SAXS), wide angle X-ray scattering (WAXS) and ambient temperature tensile testing results help to better define the nature of the hard and soft domains.