SYNTHESIS AND PROPERTIES OF MOLECULARLY UNIFORM OLIGOURETHANES WITH CHAIN-FOLDING UNITS IN THE CENTER

The study of a series of molecularly uniform poly(N-alkylurethanes) wi th a systematically varied and tailored chain architecture has shown t hat the packing and superstructure can be controlled by the primary st ructure of the urethane chain and reversibly altered by the sample tre atment, respectively. Depending on the conformation or the stereogeome try of the constitutive unit built in the middle of the otherwise symm etrical oligourethane, chain-extended and/or chain-folded crystallizat ion of the urethane chain can occur. The packing order, i.e., adjacent reentry chain-folding or chain-extended crystallization, and the ther mal properties of the oligourethanes are related to the chemical struc ture of the central constitutive unit.