The branched polystyrenes have been prepared via atom transfer radical polymerization (ATRP) using divinylbenzene (DVB)

triethylene glycol dimethacrylate (tri-EGDMA) or 1

6-bismaleimidohexane (BMIH) as the branching agent.The four-arm star-shaped polystyrene as the reference was prepared through the way of core-first using pentaerythritol tetrakis(-bromoisobutyrate) (4BrBu) as the initiator

in which

the conversion of styrene was studied using gas chromatography (GC).The consumption of the pendent vinyl group of branched polystyrene was analyzed using proton nuclear magnetic resonance (1H-NMR).The molecular weight

polydispersity index

intrinsic viscosity and mean-square radius of gyration of the branched polymers were measured by triple detection size exclusion chromatography (TD-SEC).The results showed that the pendent vinyl groups of the polymer chains were consumed gradually

and the core formation process was not observed in these polymerization systems of DVB

tri-EGDMA or BMIH.During the early stages of polymerizations

the primary chains with pendent vinyl groups and the slightly branched chains were formed

and the molecular weight of the branched polymer increased gradually with the conversion of styrene.In the later stages

owing to further reaction of the reactive species with the pendent vinyl groups of polymeric chains

the coupling reaction between polymeric chains was more obvious

resulting in sharp increase in the molecular weight of branched polymers.The obtained branched polymers prepared using DVB

tri-EGDMA or BMIH as the branching agents were all randomly branched polystyrene.