Hyperbranched and Hyperstar Polybutadienes via Anionic Self-Condensing Vinyl Copolymerization

We synthesized highly branched polybutadienes by anionic self-condensing vinyl copolymerization (ASCVCP) of a butyllithium/divinylbenzene (DVB)-based initiator monomer (inimer) and butadiene. The molecular structure of polybutadienes was evaluated by SEC with MALLS and viscosity detection. SEC/viscosity measurements confirmed the branched structure of the obtained polymers. Examination of polymerization of two isomers of divinylbenzene, i.e., para- and meta-DVB, revealed differences in the mechanism. MALDI-ToF mass spectrometric analysis in the case of p-divinylbenzene indicates macroinimer formation as the first step, followed by condensation of the macroinimers into a highly branched polymer with narrowly distributed polybutadiene segments. The living nature of the polymerization allowed further amino-functionalization of the hyperbranched polybutadienes or subsequent growth of (meth)acrylate arms leading to hyperstar molecules. The reactivity of the primary amino groups in the amino-functionalized copolymers was used in the grafting-onto reaction, i.e., amide formation with w-carboxy-poly(N-isopropylacrylamide), leading to another type of hyperstar. To the best of our knowledge, these are the first examples of hyperstars with a polybutadiene copolymer core described to date.

Automated summary

Highly branched polybutadienes were successfully synthesized via ASCVCP method, with SEC/viscosity measurements confirming the branched structure of the obtained polymers. Differences in mechanism were observed in the polymerization of two isomers of divinylbenzene. The living nature of the polymerization allowed further amino-functionalization or growth of (meth)acrylate arms, leading to hyperstar molecules.