Synthesis And Characterization Of Aqueous Two-phase Polyacrylamide Latex

Aqueous two-phase polyacylamide(PAM) latex is that the water-soluble monomers(such as AM) and another water-soluble compounds are dissolved to form a homogeneous aqueous solution, then polymerize to form a heterogeneous polymer dispersion aqueous solution. The advantages of the aqueous two-phase polymerization are the low viscosity and higher monomer concentration of the polymerization system, and such method overcomes the problems of agitation and heat release in homogeneous aqueous polymerization. Aqueous two-phase polyacrylamide latex has a convenient application because of its instant dissolvability in water. In addition, the development of the aqueous two-phase polyacrylamide latex with very broad prospects of application matches the requirement of green chemistry.The aqueous two-phase polyacylamide latex is synthesized in methanol and water mixture solvent using acrylamide and different dispersing agents as raw materials. The effects of initiator concentration, monomer concentration, concentration of dispersing agent, kinds and ratio of emulsifiers, pH values and polymerization temperature on kinetics of AM polymerization in different dispersing agents aqueous solutions initiated by single and redox initiators are investigated through intermittent reaction. The optimized conditions of synthesis of the aqueous two-phase polyacrylamide latex are obtained. The results demonstrates that the latex with higher polymer molecular weight (1.15×10⁶) can be available when redox initiators, polyvinylpyrrolidone (PVP) as dispersing agent, the composite emulsifiers of OP-10 and sodium dodecyl sulfate (SDS), appropriate temperature (about 30℃) and the appropriate pH value 6.5 are applied to the aqueous two-phase system.Kinetics research indicates that the reaction velocity are proportional to [I]0.3264, [AM]0.8421, [PVP]-7.3832 and [SDS]0.5093. The apparent activation energy of polymerization amount to 40.95 kJ·mol^-1. Getting W and CCC by means of 724-spectrophotometer and the effects of initiators, emulsifiers and pH values on electrolyte stability of the latex which is made through the method of semicontinuous addition of monomers are discussed. The results shows that CCC is increased with the dosage of initiator but tend to be a fixed value when the dosage exceed 0.15wt% and it gets a peak value when w(SDS):w(OP-10)=3:2. CCC is increased with pH values, but PAM can hydrolyze when pH>9. The suitable pH value 6.5 is adopted.The theory fitting calculations have been done using Reerink and Overbeek Approximation, DLVO theory, and the parameter A respectively amounts to 4.4×10^-15J, 3.47×10^-21J, both of which can't give a reasonable explanation of the stability of aqueous two-phase latex system.