The initial phase of styrene solution polymerizations was studied in detail for cyanoisopropyl dithiobenzoate (CyP-DB) or phenylethyl dithiobenzoate as RAFT agents. The transformation of the RAFT agent into oligomeric RAFT species and the main equilibrium of the polymerization are characterized by two chain transfer constants. The kinetic analysis is based on the measurements of the RAFT agent concentration and the molecular weight distribution by means of size exclusion chromatography with high molecular weight resolution. As shown in the plot the initialization period is ideal for temperatures ranging from 60 to 110 �C: to each cyanoisopropyl dithiobenzoate molecule one monomer molecule is added.In the case of cyanoisopropyl dithiobenzoate already after 0.6 % of monomer conversion the initial RAFT agent is consumed completely. Total transformation of phenylethyl dithiobenzoate is achieved at a slightly higher monomer conversion of 1.5 %. Employing Monte Carlo methods the chain length distributions were modeled as a function of monomer conversion to derive the chain transfer constants for the pre- and main equilibria. For example, the chain transfer constant of the main equilibrium is 1330 at 80 �C using cyanoisopropyl dithiobenzoate as RAFT agent.

Detailed experimental and Monte Carlo investigations into the early stage of RAFT polymerizations

248th National Meeting (2014)

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