Synthesis and characterization of core-shell PPY/PU/PMMA latex

Abstract

Polypyrrole/polyurethane/poly(methyl methacrylate) (PPy/PU/PMMA) core-shell particles were successfully synthesized by a three-stage polymerization process. The first stage involved the formation of NCO-terminated prepolymer based on 2,4-toluene diisocyanate and polyester polyol which was synthesized by condensation polymerization based on 1,6-hexanediol, adipic acid, and isophthalic acid. The molecular weight distribution was measured through gel permeation chromatography. Aqueous PU dispersion was then produced by self-emulsification method in which an oil phase containing NCO-terminated prepolymer, the chain extender ethylene diamine (EDA), and the neutralizing agent triethyl amine (TEA), was dispersed in the water phase. The influence of NCO/OH and TEA/DMPA molar ratios on the particle size of PU was investigated. The average particle size of some selected products was measured through dynamic light scattering. The second stage was to produce a core of PU/PMMA via soap free emulsion polymerization technique using tertiary butyl hydroperoxide (TBHP) as the initiator. The effect of the weight ratio of PU/PMMA on its particle size was also studied. The third stage was to synthesize the shell of polypyrrole over the surface of core particles. Ferric chloride and poly (N-vinylpyrrolidone) (PVP) were used as the oxidant and stabilizer, respectively, in the oxidative polymerization of pyrrole. The coverage of PPy onto the core surface was viewed by transmission electron microscopy. All the resulted products were characterized by FTIR spectroscopy. Finally, the electrochemical corrosion tests of iron disks coated with PPy/PU/PMMA films were performed. By using scanning electron microscopy, it was observed that these latex films have good corrosion resistance.