Synthesis and crystallization behavior of poly[5-(N,N-dimethylamino)-isoprene]

Anionic polymerization of N,N-dimethyl-2-methylene-3-buten-1-amine (5-(N,N- dimethylamino)-isoprene, DMAi) in toluene yields highly regio- and stereore gular polymers. The polymerization proceeds fast compared to non-polar dien es like butadiene or isoprene and polymers with almost exclusive trans-conf iguration are obtained. The amount of tuans-connected monomer units is foun d to rise with decreasing polymerization temperature and with increasing mo lecular weight to a limiting value of about 95% at 25 kg/mol. Kinetic inves tigations reveal a polymerization behavior which does not follow simple fir st- or second-order kinetics with respect to monomer concentration. Poly[5- (N,N-dimethylamino)-isoprene] (PDMAi) synthezised in this way is semicrysta lline with a degree of crystallinity of 55-60%. It shows a broad melting in terval at 70 degrees C besides a glass transition at -30 degrees C. With th e help of DSC, WAXS as well as cross-polarized light microscopy, the existe nce of two different crystal modifications is proven. The observed polymorp hism is very similar to the one known from structurally related trans-polyi soprene (TPI). (C) 2000 Elsevier Science Ltd. All rights reserved.