Date of Completion

January 1981


Chemistry, Polymer




Polystyrene latices containing only surface sulfonate groups have been synthesized using the initiator disodium bis (4-sulfomethyl benzoyl) peroxide in the absence of added emulsifiers. The initiator was synthesized through a sequence of reactions involving six steps starting from para-toluic acid.^ The initiator was used for the emulsion polymerization of styrene in the absence of added surfactants. The effect of the variation of monomer concentration, initiator concentration and ionic strength on the final number and diameter of particles was investigated.^ The latices, after purification by ion-exchanging with a mixed bed resin, were characterized by HOTS for particle size, by conductometric and potentiometric titrations for surface acid concentration and by ISS for the nature of the surface atoms. Only strong acid groups were found to be present on the surface, attributed to sulfonic acid.^ To study the hydrolysis of sucrose by strong sulfonic acid groups present on the surface of polystyrene latices, two types of latices were synthesized. One of the latices (27-4-L6) was prepared by using a Fe('3+)/HSO(,3)('-) redox initiator system and sodium dodecyl sulfonate as the emulsifier. Latex 10-5-L15, containing sulfonate and sulfate surface groups, was heated to effect the auto-catalyzed hydrolysis of the sulfate groups. After complete hydrolysis, this latex had both sulfonate and hydroxyl surface groups.^ The hydrolysis of sucrose was studied using these two latices at various initial sucrose concentrations and at different temperatures. The second order rate constants were compared with literature values for sucrose inversion by ion-exchange resins (in the H('+) form), H(,2)SO(,4), polystyrene sulfonic acid (solution in water). Rate enhancements of about 50 to 80% over H(,2)SO(,4) and about 30% over homogeneous polystyrene sulfonic acid were observed. The second order rate constants compared to ion-exchange resins in the sulfonic acid form were nearly 50 to 60 times higher. The energies of activation for the two latices were approximately 16,000 cal/mole, comparable to ion-exchange resins and much lower than those for homogeneously catalyzed reactions.^ The higher rates observed are possibly due to the high activity of the H('+) ions in the vicinity of the surface of polystyrene latex particles. Under these circumstances, it is quite possible that besides the H('+) ion, the sulfonate anions and the undissociated sulfonic acid molecules present in the Stern layer take part in the catalysis.^ No appreciable difference in the rate of hydrolysis were noticed for the two latices used, thus suggesting that the hydroxyl groups do not affect the kinetics of the hydrolysis of sucrose significantly. ^