Incorporation of Alkoxysilanes into Model Latex Systems: Vinyl Copolymerization of Vinyltriethoxysilane and n-Butyl Acrylate

The increase in industrial interest in the incorporation of alkoxysilanes in organic polymer coatings arises from their ability to form self-cross-linkable films at room temperature. In the past few years, many patents were published, offering solutions for avoiding premature cross-linking of alkoxysilane-containing latexes and for obtaining good film-forming properties without using organic solvents. The present paper proposes a miniemulsion approach for the incorporation of alkoxysilanes into acrylate latex systems in order to protect the silane moieties from hydrolysis and premature cross-linking by reducing their contact with water. Vinyltriethoxysilane (VTES)/n-butyl acrylate (BA) copolymer latexes were synthesized by both conventional emulsion and miniemulsion procedures. The amount of coagulum and conversion were determined by gravimetry. Differences in coagulum levels were observed with respect to the copolymerization procedure (1.1−32.7 wt % based on monomers in conventional systems vs 1.2−5.5 wt % on monomers in miniemulsion systems for a VTES feed of 1−50 mol %) and acrylate/alkoxysilane molar ratio. Gas chromatography was used to determine the reactivity ratios of VTES/BA pairs by analyzing the evolution of unreacted comonomers during copolymerization. The reactivity ratios between the alkoxysilane and acrylate differed by 2 orders of magnitude for VTES (monomer 1) and BA (monomer 2), where r1 = 0.044 and r2 = 8.56. These results were confirmed by FT-IR analysis of the copolymer composition (r1 = 0.086, r2 = 8.51).