No abstract

Cationic poly(N-isopropylacrylamide) (NIPAM) copolymer latexes have been prepared at 70°C using methylenebisacrylamide ( M B A ) as the crosslinking agent, 2-2'azobis-(2-amidinopropane hydrochloride) (V50) as the initiator and in the presence of 2-aminoethylmethacrylate hydrochloride (AEM). It was found that the concentration of AEM plays a major role in the polymerization kinetics and particle nucleation. However, too high a concentration (2)(3)(4)(5) caused the latex to be polydispersed together with the production of large amounts of polyelectrolytes. The presence of surface amino groups on the final particles under the protected form was revealed both by an ultraviolet spectrometry and nuclear magnetic resonance methods. It was indirectly evidenced through the electrophoretic mobility behavior of the latex particles (below and above the lower critical solubility temperature of the poly(N1PAM)) as well as by their stability against a monovalent electrolyte.

The adsorption characteristics of polyelectrolyte chains on a plane surface are derived. The approach uses the mean-field arguments first developed by de Gennes [Rep. Prog. Phys. 32, 187 (1969)] and Richmond and Jones and Richmond [J. Chem. Soc. Faraday Trans. 73, 1062 (1977)] for the evaluation of the configuration probability of a neutral chain at an interface. Electrostatic interactions among monomers are treated through the linearized Poisson–Boltzmann equation. The treatment is restricted to dilute solutions and to weakly charged polyelectrolytes. Simply analytical expressions are derived for the concentration profile and the adsorption isotherm which are expressed in terms of two characteristic lengths L1 which characterizes the range of surface forces and L2, the Debye–Hückel length, which characterizes the range of electrical forces. Once these variables are fixed, it appears that the adsorption cannot exceed a critical value Γm which is tuned by the temperature.