Preparation Of RAFT-Synthesized Macro-surfactants And Their Application In Emulsion Polymerization

Water-based paint is environmentally friendly paint because of it’s low VOC and low toxicity. Currently, water-based acrylic resin coating have became the most widely used varieties in water-borne coatings because of their excellent performance. Having advantage of small negative factors to film-forming resin, wide source of raw materials, low prices, the application of macro-surfactant in Emulsion is getting more and more attention.In this paper, different methacrylic acid(MAA) content of macro-surfactants P(MMA-co-MAA-co-n BA) were synthesized by UV-visible photoinitiation RAFT bulk polymerization. Their chemical structure were characterized by 1H-NMR and FT-IR. The molecular weight and distribution of polymer were characterized by GPC.The study to micelle behavior of macro-surfactant solution found that when the content of MAA is less than 5.0(mol)% in macro-surfactant, it can not be neutralized into hydrosol effectively; with N,N-dimethylethanolamine(DMAE) as the neutralizer,the particle size of micelle is small, it have a narrow size distribution and good emulsion stability, the cloud point of the solution is greater than 80℃; with triethylamine as the neutralizer, it have a large particle size and a wide size distribution; it will have poor stability when the emulsion is neutralized by sodium hydroxide. When the content of MAA is more than 10.0%, the pH value have a small affection on the latex particle size, the particle size of micelle has no change when the pH value increased. When the concentration of macro-surfactant is less than 0.5%, the particle size of micelle decreases with the increase of concentration, when the concentration is between 0.5% and 15%, the particle size of micelle increases with increase of concentration.The study to the conditions of the emulsion polymerization found that it was best when the reaction temperature is 80℃ and the amount of initiator is 0.2wt%. Under this condition, the P(MMA-co-MAA-co-nBA) with the content of MAA is 10.0%, 15.0%, 20.0% used as an emulsifier for emulsion polymerization is studied. The higher the acid content of the emulsifier, the higher the emulsion polymerization conversion rate; the higher the emulsifier concentration, the higher the conversion rate; the higher the solids content, the lower the conversion rate. The lower the acid content of the emulsifier, the emulsion latex particle size is smaller; the greater the concentration of emulsifier, the greater the latex particle size; the higher the solids content of the emulsion, latex particle size is smaller.In this paper, the low acid content of macro-surfactant was synthesized by one-pot method. This method have the advantage of simple experimental operation, high reaction efficiency and the emulsion coating synthesized with macro-surfactant have good water resistance.