ELECTROSTERIC STABILIZATION OF POLYMER COLLOIDS

Four electrostatic surfactants, CmH2m+1O(CH2CH2O)nSO3Na, with m averaging between 12 and 15 and n, the ethylene oxide chain length, being 3, 7, 9, or 15, were used to investigate the steric chain length effect in the stabilization of model latices and in emulsion polymerization of styrene. It was found that during polymerization, the number of particles stabilized and the rate of reaction decreased with increasing ethylene oxide chain length in the surfactant. The addition of an electrolyte to the polymerization system caused a decrease in the rate of polymerization. This electrolyte effect decreased with increasing ethylene oxide chain length. Coagulation tests of latices stabilized by these four surfactants indicated a switch in stabilization mechanism from primarily electrostatic to steric stabilization between 9 and 15 ethylene oxide units.