The role of itaconic and fumaric acid in the emulsion copolymerization of methyl methacrylate and n-butyl acrylate Maurı ´cio P. Oliveira, Domingos S. Giordani, Amilton M. Santos * Laboratory of Polymer, Department of Chemical Engineering, Chemical Engineering College of Lorena, Faenquil CP 116, 12607-970 Lorena, Sa ˜o Paulo, Brazil Received 9 March 2005; received in revised form 12 October 2005; accepted 14 November 2005 Available online 4 January 2006 Abstract The effect of itaconic (IA) and fumaric (FA) acids, in the emulsion copolymerization of methyl methacrylate (MMA) with n-butyl acrylate (BA) is presented in this work. The effect of functional monomers on the overall conversion, on the colloidal properties of the latexes as well as on the distribution of the carboxylic groups (buried, particle surface and serum) was examined. The effect of the pH on the partitioning of IA and FA on the copolymerizations was also examined in order to better understand the role of these functional monomers. The carboxylic groups present in the cleaned latexes were analyzed using conductimetry and manual titration with a solution of sodium hydroxide in methanol. The results of these analyses showed that it was possible to determine the distribution profile of the carboxylic groups in the latexes (bur- ied, particle surface and serum). It was demonstrated that IA and FA were distributed differently throughout the three phases of the emulsion, with these differences depending on the solubility of the corresponding monomer. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Functionalized latex; Methyl methacrylate; Butyl acrylate; Fumaric, itaconic, acrylic and methacrylic acids; Partitioning 1. Introduction Functionalized latexes can be produced from the emulsion polymerization of a base hydrophobic monomer and a small amount of carboxylic mono- mers. Carboxylic monomers are typically incorpo- rated in formulations of emulsion polymerization to improve the colloidal stability of the latexes used for instance as bonding agents in latex-based paper coating and surface treatments for paper products. These carboxylic monomers enhance the adhesive characteristics of the latexes on different substrates, improve the mechanical properties of the films formed from the polymer latex, improve compatibil- ity with pigments and allow the introduction of reactive groups on the particle surface for posterior reactions of chemical modification [1–3]. Common carboxylic acids are partially or totally soluble in water, and their partitioning between the organic phase (monomer droplets and/or polymer particles) and the continuous phase (water) depends on the degree of ionization of functional monomer, which in turn is a function of pH of the reaction. Moreover, the distribution of the carboxylic groups 0014-3057/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2005.11.016 * Corresponding author. Fax: +55 12 3153 3133. E-mail address: amsantos@dequi.faenquil.br (A.M. Santos). European Polymer Journal 42 (2006) 1196–1205 www.elsevier.com/locate/europolj EUROPEAN POLYMER JOURNAL