The role of carboxylic acid comonomers in morphology control of synthetic latex particles – batch reactions

Abstract

Carboxylic acid monomers are commonly added to synthetic latices to provide colloidal stability, but they are also known to affect the physical structure of composite particles. We present a systematic study of the effects of various levels of methacrylic acid (MAA) copolymerized in a styrene/butyl acrylate (S/BuA) seed latex on the morphology of composite particles when methyl methacrylate (MMA) and butyl methacrylate (BMA) are separately polymerized as second stage monomers under batch processing conditions. We find that adding up to 10wt% MAA to the S/BuA seed polymer resulted in the particle morphology changing dramatically from the base, non-acid, case. The changes were very different for the MMA and BMA second stage reactions and this was ascribed to the different polarities for these polymers as they contrast to those of the seed polymers. Thermodynamic equilibrium morphology predictions agreed quite well with the experimental results except in the MMA experiment when the MAA level in the seed polymer was 10%. This caused an apparent state of significant miscibility between the first and second stage polymers.

Acknowledgement We would like to thank the Asahi Chemical Industry Co., Ltd for its personnel and financial support of this work, Ola Karlsson and Jeffrey Stubbs for critical discussions, and the UNH Latex Morphology Industrial Consortium (AtoFina, Mitsubishi Chemicals, NeoResins, and UCB Chemicals) for partial financial support.