Radical Polymerization Of Methyl Acrylate Research Articles

Monolayers of Poly(methyl acrylate) Saponified Partially in Homogeneous and Heterogeneous Systems

Abstract Poly (methyl acrylate) prepared by radical polymerization of methyl acrylate was saponified partially in acetone-water mixtures (5 : 2 and 100 : 1 by volume), using sodium hydroxide as the catalyst. Saponification in an acetone-water mixture of a 5 : 2 ratio by volume proceeded in a homogeneous state, but the reaction solution of a 100 :1 ratio by volume was in a white-turbid state, in which saponification proceeded in a heterogeneous state. The properties of the monolayers of polymers saponified in different states were studied at the air/water interface by measuring the surface pressure. The limiting areas obtained on distilled water for each polymer saponified in these two systems decreased linearly with an increase in the degree of saponification. However, the monolayers of polymer saponified in a homogeneous system were more stable on sodium chloride solution than those obtained in a heterogeneous system, and gave the limiting areas on solutions above 5% corresponding with the theoretical values calculated from the areas per methyl acrylate and acrylic acid residue and the degree of saponification. This can be explained by the fact that some of the hydrophilic parts of the saponified polymers submerged into the water phase were squeezed out onto the water surface by the salting out effect. On the other hand, those values obtained in a heterogeneous system neither corresponded to the theoretical values nor gave reproducible areas at high concentrations. These facts may be due to the differences in the states of the saponified polymers.

PHOTO-INITIATED FREE RADICAL POLYMERIZATION OF METHYL ACRYLATE IN AQUEOUS SOLUTION

Photo-initiated free radical polymerization of methyl acrylate in aqueous solution is described. Using mainly light of wavelength 3650 Å and the ion pairs Fe3+OH− and Fe3+Cl− as photosensitizers the kinetics of polymerization were investigated by studying the effect of the variation of (i) intensity of light, (ii) concentration of monomer, (iii) fraction of light absorbed by the ion pair, and (iv) ferrous ion accumulating in, or initially added to, the system on (a) molecular weight of polymer, (b) the rate of disappearance of monomer, and (c) the rate of production of ferrous ion. The results have been analyzed in the light of a reaction scheme involving (1) a primary photochemical process and a dark back reaction, (2) initiation of polymerization by the primary product Fe2+OH or Fe2+Cl, (3) dissociation of the primary product, (4) a secondary dark back reaction, (5) initiation by a free radical, (6) propagation, and (7) termination. Examination of the experimental results in the light of the reaction scheme indicated that the initiation of polymerization was due to OH or Cl free radicals formed by the dissociation of the primary product and that termination occurred by combination of growing polymer chains. Some expressions involving specific rate constants have been evaluated.