Internal Structure of Latex Particles Formed by Two-stage Feed Polymerization

Abstract

The internal structure of the latex particles of the carboxylated poly(ethyl acrylate) formed by two-stage feed polymerization was investigated in order to obtain indirect imformation about the core-shell morphology formation by the above polymerization of two types of monomers or monomer mixtures of the same or closely similar hydrophilicity. The latex was prepared by polymerization of ethyl acrylate (EA) containing ¹⁴4C-labeled EA-methacrylic acid (MAA) (91.3: 8.7 mixture in weight) in the presence of EA-MAA copolymer seeds (same composition as in monomer mixture) or in an inversed procedure, and then dissolved progressively from the particle surfaces by increasing pH. The dissolved polymer was separated by ultracentrifigation from the undissolved particles and analyzed by a liquid scintillation counte and the acid titration method. The analytical results showed that ¹⁴C-labeled EA was distributed homogeneously from the surfaces of the particles to the centers, whereas the concentration of MAA was highest at the surfaces and decreased towards inside. This tendency was confirmed for the two samples ment