Synthesis Of SMA-g-MPEG And Use As Surfactant In Emulsion Polymerization

Amphiphilic copolymer (SMA-g-MPEG) was prepared by grafting methoxy poly (ethylene glycol) (MPEG) onto copolymers of maleic anhydride and styrene (SMA). Hydrolysis of the remaining anhydride residues gave graft copolymers carrying a number of carboxylic acid groups along the main chain. The kinetics of styrene emulsion polymerization stabilized by the graft copolymer was studied. The effect of the amount of initiator, surfactant and the reaction temperature on the kinetics of the emulsion polymerization was investigated. The results show that the polymerization rate (RP) increased with increasing graft copolymer concentration, initiator concentration and temperature. When AIBN was used as the initiator, RP and NP were proportional to 0.36 and 0.55 power of the surfactant concentration, respectively. The deviation from the Smith-Ewart caseⅡkinetics is attributed to the slow desorption rate of AIBN from the oil phase. When KPS was used as the initiator, RP and NP were proportional to 0.98 and 0.99 power of surfactant concentration, respectively. The deviation is attributed to the low efficiency in stabilizing the system because of their relatively low diffusion capability in the reaction system. The RP was proportional to 0.48 power of initiator concentration (AIBN). The particle size should decrease with increasing T. Therefore, the DDLS data obtained from the series of styrene emulsion polymerizations in decreasing order are D65℃>D70℃>D75℃≈D80℃When the temperature is above 75℃, the DDLS decreases slightly, the reason is the hydrogen bonds are weaker and CMC value decreases slightly at high temperature, so no more aggregates are available for particle nucleation. The evolution of the particle size during the polymerization was measured. The final latex distribution was bimodal because the droplet nucleation and monomolecular aggregates nucleation coexisted in the polymerization.