Radical emulsion polymerization in the presence of 3-mercapto hexyl methacrylate (MHM) as the chain transfer monomer has been carried out in this study.Potassium persulfate was used as the initiator

and sodium dodecyl benzene sulfate was used as the emulsifier.The obtained polymers were characterized using 1H-NMR and triple-detection size exclusion chromatography.The primary chain length and the average MHM content per primary chain can be adjusted by the polymerization parameters.At the same feed ratio of monomer/branching agent

the molecular weight of the primary chain and its average MHM content will be increased with increase of emulsifier concentration and decrease of polymerization temperature or initiator concentration

which is beneficial to preparing branched vinyl polymers with high molecular weights and relatively narrow polydispersities because of high conversion of the primary chain into branched molecules.Excess high emulsifier concentration

low polymerization temperature or low initiator concentration will result in gelation because of excess coupling reaction between branched molecules.Compared with results reported in the literature

branched polymers with considerably higher molecular weights and relatively narrower polydispersities have been obtained without gelation at high monomer conversions because no primary chains remain.