Syntheses And Properties Of High Solids Polyacrylate Microemulsions Based On Gemini Surfactants

Polymer microemulsion has a lot of excellent performances,such as small particle size(10~100 nm),narrow distribution,high stability,transparent and dense coating film.Microemulsion polymerization has considerable application value in the field of new materials preparation because by which the particles in a set size range could be obtained effectively.At present,the conventional microemulsion polymerization system has some defects such as high emulsifier dosage,low monomer concentration and poor water resistance and therefore limits its applications in industry.In this paper,the Gemini surfactants were introduced into the acrylate microemulsion polymerization system in order to improve the emulsifying performance,reduce the amount of emulsifier and enhance the application performance of the latex films.Firstly,a series of anionic Gemini surfactants,1,8-octanediol double itaconate diester sulfonate(Gemini n-8-n,n=12,14,16,18)were synthesized using itaconic anhydride,sodium hydrogen sulfite,long-chain fatty alcohols and polyol as the raw materials.The structures of target samples were confirmed by FT-IR and ~1H NMR.The results show that the gemini surfactants have a lower critical micelle concentration(CMC)and can be used as a good solubilizer.Secondly,the Gemini surfactants were introduced into the microemulsion polymerization system of acrylate monomers as new emulsifiers.The effects of emulsifier system,initiator system,reaction temperature and monomer ratios on the syntheses of microemulsion were discussed.The optimum reaction conditions were obtained by orthogonal test and are as follows:the amount of emulsifier was 1.5wt%,the initiator 0.75wt%,the ratio of soft and hard monomers 5/5,and the polymerization temperature 85°C.The polyacrylate microemulsion with average particle size of about 50nm and solid content of 39wt%and high storage stability and electrolyte stability were successfully prepared under the optimal synthetic conditions.The structure of synthesized polymers were verified by FT-IR and ~1H NMR,which was in complete agreement with the target product's structure.Finally,the properties of polymer microemulsion and its latex film were investigated.The results showed that compared with the common emulsion system,the polymerization system has a shorter induction period and higher final monomer conversion.Mononuclear microbead nucleation occured in the early stage of the reaction,and there were always micelle nucleation during particle growth,which means continuous nucleation.The TEM images exhibited that the products consisted of a number of colloidal particles with particle size of about 40~50 nm and monodisperse and regular spherical particles.The products were stored for more than 120 days with high stability,and the electrolyte resistance and low temperature resistance were also excellent.Gemini emulsifier can reduce the water absorption of the latex film,and the water absorption decreased as the number of carbon atoms in the hydrophobic chain increases,thereby improving the water resistance.The thermal stability and the glass transition temperature of the latex film was significantly improved as the number of carbon atoms in the hydrophobic chain of the Gemini emulsifier increased.When the acrylate microemulsion was used as a fabric printing adhesive,the film formation exhibited high transparency.The series of products have high dry and wet friction fastness(Grade 4-5),and the fabric was soft to the touch and was not prone to pilling.