Polymers and polymerization processes
Emulsion polymerizations are described in which the monomers include an ethylenically unsaturated ammonium phosphate ester monomer. The processes may be conducted with high total solids, to produce a polymer latex having a solids content in the range 20 to 60%, for instance in the range 25 to 50% by weight. Preferably comonomers include lower alkyl and higher alkyl methacrylate selected to give desirable glass transition temperatures and coalescing films, zwitterionic comonomers, polyethoxylated comonomers to confer desired biocompatibility and latex stability as well as good wetting for a film formed of the polymer and may contain crosslinking monomers, reactive monomers, anionic monomers and/or cationic monomers. The latexes are stable, even when the process is carried out in the substantial absence of non-polymerizable emmulsifier. Coatings formed from the latexes containing zwitterionic comonomer have good biocompatibilizing properties.
1. A coating process in which a dispersion of polymer particles in an aqueous continuous phase, having a polymer concentration in the range 20 to 60% by weight, based on total weight of dispersion, an average particle diameter of less than 1 μm, the polymer being formed from radical polymerised ethylenically unsaturated monomers comprising water-insoluble monomer and ammonium phosphate ester zwitterionic monomer is coated onto a substrate to form a liquid coating on a surface thereof, and water is removed from the liquid coating to form a stable solid polymer coating on the said surface.
2. A coating process according to claim 1 in which the water is removed by evaporation and the polymer particles coalesce during the evaporation of water to form a solid polymer film on the surface.
3. A coating process according to claim 1 in which the surface bearing the solid polymer coating is contacted with an aqueous biological liquid.
4. A coating process according to claim 3 in which the biological liquid is selected from blood and serum.
5. A biocompatibilising process in which a substrate is biocompatibilised by coating it with a dispersion of polymer particles in an aqueous continuous phase, having a polymer concentration in the range 20 to 60% by weight, based on total weight of dispersion, an average particle diameter of less than 1 μm, the polymer being formed from radical polymerised ethylenically unsaturated monomers comprising water-insoluble monomer and ammonium phosphate ester zwitterionic monomer to form a liquid coating thereon and removing the water from the liquid coating to leave a stable coating of solid polymer on the surface, whereby the coated surface of the substrate has improved biocompatibility as compared to the uncoated surface.