Study on preparation and solution properties of hydrophobically associating polyacrylamide by emulsifier-free ultrasonic assisted radical polymerization

Abstract

Through ultrasonic assisted radical polymerization, hydrophobically associating polyacrylamide (U-HAPAM) was prepared by acrylamide (AM), 2-acrylamido -2- methyl propane sulfonic acid (AMPS), and long-aliphatic-chain hydrophobic monomer octadecyl acrylate (ODA). The effects of ultrasonic frequency power on total monomer conversion, relative molecular mass and the aqueous solution behavior were discussed. The results showed that, when the ultrasonic power was 120 W, there was a good thickening ability, total monomer conversion was 76.36 %, relative weight-average molecular mass was 72500, the critical association mass concentration (C*) was 0.27 wt% and there were good intermolecular hydrophobically associating interactions in the copolymer aqueous solution. U-HAPAM was pseudoplastic fluid; the associating behavior of the U-HAPAM had apparent effects on the dynamic moduli (G′and G″) and the apparent average aggregate size (d*). When mass concentration of copolymer (C_m) was 0.40 wt%, the apparent viscosity attained 453.6 mPa·s. The viscosity retention index (VRI) was 60.99 % as the temperature reached 80 °C. The apparent viscosity of U-HAPAM in mineralized water was increased towards 502.9 mPa·s as the degree of mineralization (M) was 19334 mg/L. Under the effect of ultrasounds, the ODA was effectively introduced into U-HAPAM without micromolecule emulsifier, which endowed the copolymer good solution properties.