In-situ and real-time observation of living anionic polymerization process and polymerization-induced self-assembly of polyisoprene-b-polystyrene-d8

Zhao, Y.; Miyamoto, Nobuyoshi; Koizumi, Satoshi; Hashimoto, Takeji

The simultaneous living anionic copolymerization of isoprene (I) and styrene-d8 (S) monomers, initiated by sec-butyllithium in benzene-d6, was investigated by means of time-resolved SANS, UV-Vis spectroscopy, SEC, and NMR. The results revealed the 3 time regions. In region 1, random copolymers rich in isoprene (80 wt%) were synthesized. SANS intensity was weak and almost time-independent, and UV-vis absorbance at 450 nm was very weak. In region 2, styrene-d8-rich random block sequences were formed to result in the block copolymers. A broad scattering peak appeared in SANS, aggregation number changed from 4 to 2 at the end of this region. In region 3, the remaining S underwent a rapid polymerization into polystyrene (PS), leading to the formation of P(I-ran-S)-block-P(S-ran-I)-block-PS. Polymerization-induced disorder-to-order transition and order-to-order transition from hex-cylinder to lamella occurred.