Influence of Poor Solvents on Radical Polymerization of Styrene

Abstract

Radical polymerizations of styrene were carried out in the presence of poor solvents for polystyrene at 60°C. The 40 vol% addition of 2-propanol caused the solution turbid and precipitation of polystyrene, but no turbidity was observed below the 30 vol% addition. For both hexane and cyclohexane addition, turbidity and precipitate were not observed below the 50 vol%. Kinetic orders of the monomer in hexane, cyclohexane and 2-propanol were 1.6, 1.4 and 1.3, respectively. Kinetic orders of the initiator in these poor solvents were 0.5. The values of k_t/k_p² were derived from the slopes of 1/P_a vs R_p (rate of polymerization)plots. For the homogeneous solution systems k_t/k_p² was proportional to the reciprocal of the viscosity of the system. But at the 2-propanol concentration above 40 vol% the plots deviated from the relation to indicate the increase of termination rates.