Surfactant-free aqueous RAFT polymerization of styrene in the presence of CaCO3 particles

Abstract

A new method to achieve well-controlled surfactant-free aqueous RAFT polymerization of styrene initiated by K2S2O8 in the presence of CaCO3 particles was proposed. It was found that the hydrophobic monomer of styrene was adsorbed on the surface of CaCO3 particles and well-controlled surfactant-free aqueous RAFT polymerization mediated with the RAFT agent of S,S′-bis(α,α′-dimethyl-α″-acetic acid) trithiocarbonate (BDMAT) was achieved. The weight ratio of the feeding CaCO3 to the styrene monomer on the aqueous RAFT polymerization was investigated, and it was found that high CaCO3/styrene weight ratio led to fast aqueous RAFT polymerization. The aqueous RAFT polymerization kinetics was checked, and the fast RAFT polymerization rate at low molar ratio of styrene/BDMAT/K2S2O8, the linear ln([M]o/[M])–time plot, the linear increase in the number–average molecular weight with the monomer conversion, and the relatively low PDI values (1.1∼1.3) were demonstrated. The surfactant-free aqueous RAFT polymerization was compared with the general emulsion RAFT polymerization in the presence of the sodium dodecyl sulfate (SDS) surfactant. It was found that the surfactant-free aqueous RAFT polymerization seemed more valid than the emulsion RAFT polymerization. The proposed method is believed to be a new strategy to achieve well-controlled surfactant-free aqueous RAFT polymerization.