MULTIPHASE MATERIALS WITH LIGNIN .2. STARLIKE COPOLYMERS WITH CAPROLACTONE

Multiphase starlike copolymers have been prepared using polycaprolactone as hard, arm segments and hydroxypropyl lignin as the core of the star. Copolymer architecture differed in terms of the average number of arms per core, which ranged between 2 and 7; and in terms of hydroxypropyl lignin molecular size and T-g, which ranged between 2100 and 6400 D and -7 and +85 degrees C, respectively. The copolymers, which had;nearly uniform but broad molecular weight distributions, were analyzed with regard to solution properties, thermal characteristics, and crystallinity. The Mark-Houwink-Sakurada exponential factor remained virtually constant (i.e., ca. 0.66) for all copolymer types. The thermal characteristics were all in support of multiphase morphology, and they differed with copolymer architecture. Copolymers having hydroxypropyl lignin with T-g's greater than the T-m of caprolactone resulted in significant T-m depression, whereas this could not be observed for copolymers with low T-g cores. T-m increased with arm length as the degree of polymerization of the caprolactone rose to 50. Crystallinity was established for all copolymers, even those with arms shorter than 10 caprolactone units in length.