SYNTHESIS AND CHARACTERIZATION OF CORE/SHELL IONOMERIC LATEXES .1. LATEX AND FILM PROPERTIES

This research work involved studies on the synthesis and characterization of core/shell ionomeric latexes in order to understand the process of ionic aggregate formation. The core/shell structure of the ionomeric latexes prepared in this study confines the ionic domains to the copolymeric matrix within the shell polymer, and in addition, benefits from the ionomeric properties and core/shell structure simultaneously. Core/shell ionomeric latexes with polystyrene cores and styrene/n-butyl acrylate/methacrylic acid terpolymer shells were synthesized by a semicontinuous seeded emulsion copolymerization process. The distribution of the methacrylic acid in the core/shell latexes was determined using conductometric titration techniques. The results of the conductometric titration analysis indicate that the principal locus of the carboxyl groups in the core/shell latexes is at the particle surface, but specific information about the differences in the distribution of methacrylic acid inside the latex particles could not be obtained. Mechanical characterization of the core/shell ionomeric latex films was carried out to understand the structure-property relationships using Dynamic Mechanical Analysis (DMA) and tensile testing. It was discovered that the core/shell latexes exhibited significantly different properties, owing to the differences in the overall carboxyl content and surface loading. Extensive studies were carried out to study the effect of water plasticization on the mechanical behavior of the core/shell ionomeric latex films; water adsorption causes the solvation of ionic aggregates. A preliminary investigation of the effect of the type of counterion used for the neutralization of carboxyl groups on the properties of core/shell ionomeric latex films was also carried out. (C) 1995 John Wiley & Sons, Inc.