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 ω-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.