Mechanism of Soap-Free Emulsion Polymerization of Styrene and 4-Vinylpyridine: Characteristics of Reaction in the Monomer Phase, Aqueous Phase, and Their Interface

Abstract

The characteristics of reactions in the monomer phase, aqueous phase, and the interface of monomer/aqueous phase of soap-free emulsion polymerization of 4-vinylpyridine (4VP) and styrene (St) system were evaluated by using the different types of initiators, addition of organic solvents, and changes of agitation rate. The oil-soluble initiators 2,2‘-azobis(2,4-dimethylvaleronitrile) (ADVN), benzoyl peroxide (BPO), and 2,2‘-azobis(isobutyronitrile) (AIBN), the organic water-soluble initiator, 2,2‘-azobis(2-amidinopropane) dihydrochloride (V50), and the inorganic water-soluble initiator, potassium persulfate (KPS), were used. 1H NMR and scanning electronic microscopy (SEM) were employed for the characterizations. As a result, the mechanism of interfacial particle formation was supported. Namely, the minimonomer droplets were generated by the disturbance in the interface of monomer/aqueous phase due to the agitation. The minimonomer droplets were stabilized by the adsorption of surface-active oligomer generat...