Application of the "strathclyde route" to branched vinyl polymers in suspension polymerization: architectural, thermal, and rheological characterization of the derived branched products

Copolymerizations of methyl methacrylate (MMA) and ethyl acrylate (EA), both monofunctional monomers, with ethylene glycol diacrylate (EGDA) as the brancher (a difunctional monomer) have been carried out via free-radical solvent-free suspension polymerization using 2,2′-azobis(isobutyronitrile) (AIBN) as the source of radicals, in the presence of a chain transfer agent (CTA) to avoid cross-linking and produce only branched polymers. Investigation of various CTAs led to the choice of 1-dodecanethiol (DDT) mainly due to its low volatility and hydrophobicity. Typically, EGDA/DDT mole ratios of ≤0.7 ensure that cross-linking is avoided. The molar mass and the branching architecture of the polymers have been characterized by MALS/SEC and the thermal and rheological behavior by DSC and melt rheology, respectively. The results confirm earlier indications from solution and emulsion polymerizations of the versatility of the 'Strathclyde methodology' in producing branched polymers, in this instance in the form of free-flowing spherical particulates and have allowed demonstration of the differences in the thermal and rheological behavior of the branched products relative to their linear analogues