SYNTHESIS AND PROPERTIES OF SEGMENTED POLY(ETHER-URETHANES) WITH SPECIALLY DESIGNED AND SYMMETRICALLY CHAIN-FOLDING POLY(N-ALKYLURETHANE) HARD SEGMENTS

The study of a series of segmented poly(ether-urethanes) with highly f lexible poly(oxytetramethylene) soft segments and especially designed, molecularly uniform poly(N-alkylurethane) hard segments based on pipe razine and 1,4-butanediol bischloroformate has shown that size, shape and perfection of the hard domains can be varied by both the primary s tructure of the urethane chain and the sample history. Depending on th e conformation or the stereogeometry of the built-in central constitut ive hard segment unit, chain-extended or chain-folded hard segment cry stallization, i. e., the formation of cylindrical or lamellar shaped h ard domains can be achieved. These thermoplastic elastomers exhibit di stinctly different properties which correlate systematically with the supermolecular structure and the corresponding hard segment architectu re, respectively.