GLOBAL CONFORMATIONS OF CHIRAL POLYISOCYANATES IN DILUTE-SOLUTION

Global conformations of chiral polyisocyanates were discussed in terms of light scattering and viscosity data collected for stereospecifical ly deuterated poly(hexyl isocyanate)s, poly((R)-2,6-dimethylheptyl iso cyanate) (PNIC), and copolymers of hexyl isocyanate (HIC) with (R)-2,6 -dimethylheptyl isocyanate (NIC). The light scattering data and viscos ity data obtained were analyzed consistently in the framework of the w orm-like chain model. The persistence length q was the same for PHIC a nd deuterated PHIC, but increased with the mole fraction of MC in the HIC-NIC copolymers, e.g. from 41 to 56 nm in hexane at 25 degrees C. T he results were not detailed enough to substantiate the broken worm mo del in line with the helix reversal model of Lifson et al. Gel permeat ion chromatographic behavior of the polyisocyanates was also examined, so that it could be used for the determination of the molecular weigh t distribution of a sample with a very minute amount (at most 1 mg or less). (C) 1998 Elsevier Science Ltd. All rights reserved.