Photopolymerization of styrene ( St ) with benzyl N

N-diethyldithio carbamylacetate( BzDCA) was studied.It was found that the number-average molecularweight(Mn)of polystyrene and the conversion increase with the increasing ofreaction time

respectively. The conversion also increased with the concentration of BzDCA

while Mndecreased with the increasing of BzDCAconcentration . When [ St]/[BzDCA] = 874

the Mn of PS had alinear relationship with the conversion

and agreed well with that calculated from the initial St and BzDCA concentrations and the conversions. The mechanism of the polymerization was proposed and the polymerization proceeded via a "living" radical polymerization mechanism. Under Uv irradiation

BzDCA dissociates into two kinds of radicals:carbon-Centered radical and sulfur-centered radical.The primary carbon-centered radical can initiate monomer polymerization and the sulfur-centered radical can reversibly terminate with propagating radical and form a diethyldithiocarbamate(DC) end group.