One-stage photoinitiated RAFT dispersion polymerization – Reaction parameters for achieving high particle size uniformity

One-stage photoinitiated RAFT dispersion polymerization (PRDP) has been studied. It was found that the structure of the RAFT agent has a strong influence on the particle morphology . Carboxyl-functionalized trithiocarbonates, including S,S′-bis(α,α′-dimethyl-α″-acetic acid) trithiocarbonate (BDMAT), S-1-dodecyl-S′-(α,α′-dimethyl-α″-acetic acid) trithiocarbonate (DDMAT), S-1-ethyl-S′-(α,α′-dimethyl-α″-acetic acid) trithiocarbonate (EDMAT), were found to be suitable RAFT agents for preparing highly monodisperse microspheres . GPC traces suggested that the polymerization does not follow the typical controlled/living process due to the low RAFT agent concentration in comparison with photoinitiator concentration. Particle size and uniformity changed very little with a wide range of concentrations of the stabilizer and photoinitiator. Highly monodisperse microspheres were obtained even at low stabilizer concentration (5 wt% PVP). Increasing the monomer concentration led to an increase in particle diameter with an exponent of 0.63, which is similar in scale to conventional dispersion polymerization . The microspheres were monodisperse at monomer concentrations ranging from 5 to 15 wt%.