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In a previous paper [1], the synthesis of various polystyrenepoly[NIPAM] core-shell latexes bearing cationic amidino and/or amino charges has been described. Several colloidal properties of these cationic latexes have been characterized such as: particle size, surface charge density, electrophoretic mobility and finally colloidal stability. Due to the poly[NIPAM]-rich layer in the shell, it was found that temperature played a significant role on all these properties, a LCST around 33°C being exhibited. In addition, ionic strength was also found to affect the colloidal behavior of these latexes, the largest effect being observed with latexes having both amidino and amino surface charges. The critical coagulation concentrations (CCC) of the various latexes above and below the LCST were determined, highlighting the contribution of electrostatic and steric repulsive forces to the stability of these particles.

ABSTRACT:The colloidal and surface properties of copolymer latex particles prepared by batch emulsifier-free emulsion polymerization of styrene with two different aminocontaining monomers (Amino Ethyl Methacrylate Hydrochloride (AEMH) and Vinyl Benzyl Amine Hydrochloride (VBAH)), and 2,2-azobis(2-amidinopropane) dihydrochloride (V50) as initiator were investigated. The final particle size was found to decrease with increasing the functional monomer concentration. Different titration methods were used to quantify the surface amino (brought by the monomer) and amidino groups (originated from the initiator) on the latex particles. The same behavior was observed on both type of latexes: increasing the functional monomer concentration caused the surface amino groups density to increase from 0 to a plateau value at 8.2 mC/cm 2 , whereas the surface amidino groups density decreased from 18.5 to 2 mC/cm 2 . These results were confirmed by electrophoretic measurements and they corroborated those obtained in a previous kinetic study (Part 1) concerning the role of functional monomers as transfer agents.