Synthesis Of Hydrophobically Modified Cationic Polyacrvlamide With Methyl Methacrylate By Aqueous Two-phase Polymerization And Its Solution Properties

A hydrophobically modified cationic polyacrylamide was synthesized in poly(ethylene glycol)(PEG) aqueous solution by aqueous two-phase copolymerization using acrylamide (AM) as monomer,2-methylacryloylxyethyl trimethyl ammonium chloride (DMC) as cationic monomer, and methyl methacrylate (MMA) as hydrophobical monomer. Firstly, the effects of DMC/MMA molar ratio, monomer concentration, polymerization temperature, initiator concentration and PEG concentration on the properties of copolymer were studied, and aqueous dispersed solution of AM-DMC-MMA copolymer with good fluidity and high stability was prepared. Secondly, the effects of MMA on the aqueous two-phase copolymerization rate, phase separation process, molecular and distribution of copolymer, viscosity, droplet size and micro-morphology of copolymerization system were analyzed, and it was found that MMA could exert a series of influences in the aqueous two-phase copolymerization process. Finally, the effects of shear rate, copolymer concentration, copolymer constituent, temperature and salt concentration on the rheological property of the hydrophobically modified cationic polyacrylamide aqueous dispersed solution were investigated.The momomer conversion was determined by an improved bromating method. The apparent viscosity of copolymer product was tested with a rotational viscometer. The molecular and distribution of copolymer was measured with gel permeation chromatography. Results showed that the copolymer molecular weight increased and the apparent viscosity decreased with the decreasing of DMC/MMA molar ratio, that the copolymer molecular weight and the apparent viscosity both decreased firstly and then increased with the increasing of initiator concentration, that increasing the monomer or PEG concentration both led to increasing the copolymer molecular weight and the apparent viscosity, and that improving polymerization temperature could decrease the copolymer molecular weight and the apparent viscosity.By comparing the aqueous two-phase copolymerization of AM/DMC/MMA with that of AM/DMC, the effect of MMA on the copolymerization process was revealed that MMA could not only accelerate the copolymerization rate and increase the apparent viscosity, but also cause that more polymer molecules with short chain were generated during the process. A UV spectrophotometer was used for on-line measurement of the phase separation process, finding that increasing MMA concentration could decrease the critical conversion and the critical molecular weight, which demonstrated that MMA had the function of prompting the phase separation. One point was illustrated that MMA could prompt the formation of mature droplets and accelerate the growth of droplets by using a laser particle size analyzer and a transmission electron microscopy.Through measurements on the rheological properties of copolymer aqueous solution, it was revealed that when the copolymer concentration increased for the same copolymer, the apparent viscosity and the consistency index increased, and the flow exponent decreased; but when the content of MMA in the copolymer increased for the same copolymer concentration, the apparent viscosity and the consistency index decreased, and the flow exponent increased. Increasing the content of MMA in the copolymer contributed to decreasing the viscous flow activation energy of copolymer solution, which suggested that the dependence of the apparent viscosity on temperature weakened. The addition of salt caused that the apparent viscosity declined dramatically at first, and then tended to be constant. Moreover, the copolymer chains compacted tightly because of the addition of salt; as a result, the effect of shear rate on the apparent viscosity could be neglected.