Correlation between Molecular Weight and Chemical Composition of Poly(styrene-co-acrylate) Synthesized by RAFT Copolymerization

Poly(styrene- co -methyl acrylate): SMA, poly(styrene- co -tert butyl acrylate): StBA and poly(styrene- co -methyl methacrylate): SMMA were synthesized by reversible addition-fragmentation chain transfer (RAFT) method. The relationship between the molecular weight and the styrene content was investigated by UV–RI dual detection size-exclusion chromatography. In the SMA and StBA of short polymerization time samples, the styrene content showed a tendency to decrease from the low molecular weight region toward the high molecular weight region. On the other hand, the styrene content tended to increase from the low molecular weight region toward the high molecular weight region in the long polymerization time copolymer samples. The SMMA samples showed no trend of similar changes as SMA and StBA. We have concluded that the phenomenon may be due to the difference in the chain length dependence of the equilibrium constants for the pre-equilibrium and main-equilibrium of the RAFT process.