Emulsifier‐free polymerization in aqueous media

Abstract

The polymerization in solution of a variety of water‐soluble monomers with a variety of water‐soluble redox initiators is described and a detailed study is reported on the polymerization, in aqueous solution, of methyl vinyl ketone and of methyl methacrylate under the influence of potassium sulfate‐silver nitrate. Keeping the persulfate concentration constant and varying the silver nitrate or, conversely, keeping the silver nitrate constant and varying the persulfate, it is found that, except at very high concentration of catalyst, both the rate of polymerization and the molecular weight of the polymer bear a linear relation to the square root of the catalyst concentration, in harmony with the general theory of catalyzed bulk and emulsion polymerization. The molecular weight of the polymer formed diminishes with increase in the temperature of polymerization. The study of redox polymerization in water, without emulsifier, has been extended to the case of a mixture of a water‐soluble and a water‐insoluble monomer, and it has been found that copolymerization proceeds at a reasonable rate and frequently forms a stable latex. The copolymerization of styrene and 5 or 10 per cent of its weight of methacrylonitrile in water under the influence of a water‐soluble persulfate‐bisulfite redox pair has been examined with some closeness. Polymerization is apparently initiated in the aqueous solution, since, contrary to the state of affairs in emulsion polymerization, water‐soluble retarders are more effective than oil‐soluble ones, when the retarder is added at the outset. If the retarder is added at a later stage of polymerization, oil‐soluble reagents are more effective than water‐soluble ones. The water‐soluble monomer enters into the polymer at a greater rate than the water‐insoluble one, but it appears that, even at the earliest stage at which it is practicable to take samples co‐polymerization occurs. The influence of catalyst concentration on the rate of polymerization, the molecular weight of the polymer, and the latex particle size was examined.

Aqueous polymerization of methacrylamide initiated by potassiumpersulfate-L-cystein hydrochloride redox system

“…It clearly indicates that the rate increases up to a certain limit of activator concentration and thereafter the maximum conversion and initial rate of polymerization decreases. Such a trend has earlier been reported in serveral other redox initiated polymerizations [3,17].…”

Vinyl polymerization: Kinetics of Ce(IV)–acetophenone‐initiated polymerization of acrylonitrile in acetic–sulfuric acid mixtures

“…(9) and (10). (11) kP2/kt values were obtained from the reciprocal of the product (intercept X [Ce(IV)] X [AP]), and ko/ki values were obtained from (slope/intercept) X [Ce(IV)]. Correlation of these composite rate constants in the case of substituted acetophenones with substituent parameters will be reported in subsequent papers.…”

Methacrylic Polymers

“…Polymerization takes place within the monomer droplets and, therefore, follows a course consistent with the behavior of a bulk polymerization (65,73). Ideally, there are no transfer processes taking place between the aqueous continuum and the monomer droplets during these polymerizations.…”