Hyperbranched polymers from divinylbenzene and 1,3-diisopropenylbenzene through anionic self-condensing vinyl polymerization

Hyperbranched polymers were synthesized using anionic self-condensing vinyl polymerization (ASCVP) by forming ‘inimer’ (initiator within a monomer) in situ from divinylbenzene (DVB) and 1,3-diisopropenylbenzene (DIPB) using anionic initiators in THF at −40 °C. The reaction of equimolar amounts of DVB and nBuLi results in the formation of hyperbranched poly(divinylbenzene) through self-condensing vinyl polymerization (SCVP). The hyperbranched polymers were invariably contaminated with small amount of gel (<15%). No gelation was observed when using DIBP with anionic initiators. The presence of monomer–polymer equilibrium in the SCVP of DIPB restricts the growth of hyperbranched poly(DIPB). The inimer synthesized from DIPB at 35 °C undergoes intermolecular self-condensation to different extent depending on the nature of anionic initiator at −40 °C. The molecular weight of the hyperbranched polymers was higher when DPHLi was used as initiator. A small amount of styrene ([styrene]/[Li+]=1) was used to promote the chain growth by inducing cross-over reaction with styrene, and subsequent reaction of styryl anion with isopropenyl groups of inimer/hyperbranched oligomer. The hyperbranched polymers were soluble in organic solvents and exhibited broad molecular weight distribution (2<Mw/Mn<17).