Studies Of Cationic Polyelectrolytes Prepared By Precipitation Polymerization In Salt Solution

The synthesis of cationic polyelectrolytes copoly(acrylamide-2-methyl acryloyloxyethyl trimethyl ammonium chloride) [P(DMC-AM)] by precipitation polymerization in salt solution was studied. The salt solution was screened out, and it was found that the best capable salt was potassium citrate. The copolymer, which had dispersing particles pattern and had the molecule structure character consisting of acrylamide(AM) and cationic monomer 2-methyl-acryloyloxyethyltrimethylammonium chloride(DMC), were prepared by precipitation polymerization in potassium citrate solution using ammonium persulfate ((NH₄)₂S₂O₈) and sodium sulfite (Na₂SO₃) as initiators.At first, the solubilities of DMC, AM and P(DMC-AM) in potassium citrate solution were measured respectively. According the theory of solubility parameter, it was sure that the soluble ability of DMC and AM was far more than that of P(DMC-AM), and mechanism of copolymer precipitated in the potassium citrate solution was discussed. Then the rule of solution resistance varied with various components in salt solution was inspected by colloid electricity properties, and the solution resistance changed in the polymerizing and precipitating process could also be performed. The extent of polymerization could be determinated by the solution resistance at the different reaction time in the system simultaneously.Through single-factor experiment, the conditions for monomers conversion, cationic degree of copolymer and salt residue in copolymer were optimized as follow: CD for the better monomers coversion, that salt mass fraction=56%, monomers mass fraction=3.5%, m(DMC) : m(AM) =3 : 1, initiator mass fraction=0.08%, polymerization temperature=50℃,reaction time=2h, and the monomers conversion was 87.3%;(2) for the better cationic degree of copolymer, that salt mass fraction=57%, monomers mass fraction=5%, m(DMC) .' m(AM)=6 .' 1, initiator mass fraction=0.1%—0.12%, polymerization temperature=50°C, reaction time=2h, and cationic degree of the copolymer was 80.6%;? for the least salt content in the copolymer, that salt mass fraction=53%, monomers mass fraction=l%, m(DMC) .' m(AM)=l '. 1, initiator mass fraction=0.06%, polymerization temperature=45 °C to 50 °C, reaction time=2h, and the salt residue in copolymer was 1.87%.At last, the distribution of copolymer grain diameters and micrographs (highly contrasted) of copolymer particles of P(DMC-AM) were examined. When salt mass fraction=55%, monomers mass fraction=4%, m(DMC) '. m(AM) =3 11, initiator mass fraction=0.08%, polymerization temperature=50°C and reaction time equals to 2h, the monomers conversion could be reached 80.1%, the cationic degree of copolymer could be got 57.3%, salt residue in copolymer products was 2.64%, distribution of copolymer grain diameters were from 18.7 um to 20.1um. Having analysed by IR spectrum, it was certain that the copolymer product produced by precipitation polymerization was poly(acrylamide-2-methylacryloyloxyethyltrimethyl ammonium chloride) [P(DMC-AM)].