Studies On The Synthesis Of Amphoteric Polyacrylamide By Aqueous Dispersion Polymerization

As the main research areas of functional polymers, amphoteric copolymers with the cationic monomer and anionic monomer proved significant special effects. Up to now, the water-soluble acrylamide-based polymers and copolymers could be prepared through solution polymerization, emulsion polymerization, and so on. However, there are some disadvantages associated with these processes. Dispersion polymerization of acrylamide in aqueous salt solution is a new attractive alternative to other polymerization processes. And it is a unique method due to the inherent simplicity of its single-step process, and it does not employ any organic solvent. Amphoteric polyacrylamide synthesized by aqueous dispersion polymerization is a kind of important water-soluble polymer that can be applied especially to flocculation, petroleum recovering and papermaking, etc. Unfortunately, the synthesis of copolymers by dispersion polymerization in the ammonium sulfate aqueous solution is not readily disseminated except through the patent literatures, and very little is given to the amphoteric polyacrylamide. In this study, preparation of amphoteric polyacrylamides by dispersion polymerization in aqueous solution of ammonium sulfate was described. And the mechanism of the dispersion polymerization for this system has been proposed, the main contents and results are as follows:1. The state-of-the-art as well as the developmental tendency of the synthesis of amphoteric polyacrylamide by aqueous dispersion polymerizationin was summarized.2. As the preparation of water-soluble polymer usually choose a special dispersant in the way of dispersion polymerization, a series of different types and molecular weight of dispersants were synthesized by solution polymerization, such as cationic dispersants poly(methacryloyloxyethyltrimethyl ammonium chloride) (PDMC), poly(diallyl dimethyl ammonium chloride) (PDADMAC), poly(acryloylxyethyltrimethyl ammonium chloride)(PDAC), polyacrylic acid (PAA) and anionic dispersants sodium polyacrylate(PANa). Discussion was also made for the characterization of the polymers. 3. Dispersion polymerizationin of P(AM-co-AA-co-DADMAC) has been successfully carried out. The copolymer obtained was characterized using FTIR, NMR, chloride Mohr titration, acid-base titration and SEM. The effects of ammonium sulfate and dispersant concentration, the molar ratio of anionic monomer to cationic monomer on the stability of the dispersion were investigated. The results show that amphoteric uniform-sized copolymer could be obtained under the following optimized conditions:concentrations of 1.8wt%-2wt% for PDADMAC,23wt%-29wt% for ammonium sulfate, pH in the range of 2-4 and the DADMAC/AA/AM molar ratio is about 1/1/2. Discussion was also made for the characterization and flocculation ability of the copolymers.4. In a similar way, with AM, AA. DAC and DMC as the source monomers, amphoteric copolymer P(AM-AA-DAC-DMC) was synthesized by dispersion polymerizationin in the solution of ammonium sulfate. The characteristics of copolymer were studied by means of FT-IR, 13C-NMR, TEM and other methods. The effects of different dispersants, the molar ratio of anionic monomer to cationic monomer and pH on dispersion polymerization conditions and the stability of the dispersion were investigated. The results show that amphoteric nano-copolymer with more than 25% ion exponent could be obtained under the following optimized conditions polyvinylpyrrolidone (PVP), PDMC and PDAC as polymeric stabilizers, pH≤4, the molar ratio of ionic monomer to cationic monomer is less than 1.