SURFACE CHARACTERIZATION OF AMINE-CONTAINING LATEXES BY CHARGE TITRATION AND CONTACT-ANGLE MEASUREMENTS

Surface properties of cationic amino-containing latexes, as obtained b y emulsifier-free emulsion copolymerisation of styrene with vinyl benz yl amine hydrochloride using 2,2'-azobis (2-amidinopropane) dihydrochl oride (V50) as initiator, were investigated. Surface charge density wa s first examined using H-1 NMR, conductometry and two spectroscopic me thods (UV, fluorescence). Whereas the first two methods only provide s emi-quantitative information on the overall surface density, the latte r two were more accurate and suitable for discriminating amidine (issu ed from the initiator) and amine (brought by the cationic monomer) sur face groups. In addition, it was possible to show differences in the n ature of surface groups according to the mode of polymerisation proces s (batch versus shot-growth). Latex surface polarity was examined thro ugh contact angle measurements which allowed one to determine surface tension using the mean harmonic approximation method. Such amino latex es were found to exhibit a much lower surface polarity than sulphate-c harged ones. (C) 1998 Elsevier Science B.V.