Branched styrene–acrylic resin for coating via radical polymerization in the presence of chain transfer monomer

Branched styrene–acrylic resins were prepared through radical polymerization using cheap 2-(3-mercaptopropionyloxy) ethyl methacrylate (MPOEM) as the chain transfer monomer (CTM). The monomers were added dropwise into the reaction vessel containing xylene at 135°C to obtain styrene–acrylic resins. The formation of branching and the molecular weight were analyzed using triple detection size exclusion chromatography (TD-SEC). The viscosities of the resins were characterized using rotational rheometer and Grignard tube viscometer. By adjusting the dosage of MPOEM and the initiator, a series of branched styrene–acrylic resins were obtained. Generally, the viscosity and the flow ability of the resin were improved evidently when branching was introduced. At the mole ratio of monomer to MPOEM of 100/0.1, the branched styrene–acrylic resin showed 51% decrease in zero-shear viscosity and 62% increase in flow ability, compared with the linear analogues with similar molecular weight at 70% solid content.