Preparation and self-assembly properties of silicone-modified hydrophobically associating polyacrylamide

Abstract

Silicone-modified hydrophobically associating polyacrylamide (USPAM) was prepared by emulsifier-free ultrasonically assisted radical polymerization with acrylamide (AM), dimethylvinylphenylsilane (DMPS), and 2-acrylamido-2-methylpropane sulfonic acid (AMPS). Various aspects of the copolymerization reaction and the effects of salt, temperature, and surfactant (sodium dodecyl sulfate, SDS) on the self-assembly behavior of USPAM were studied through viscometry, fluorescence spectroscopy (FS), laser light scattering (LLS), rheology and other methods. The results showed that the optimal polymerization conditions were: contents of DMPS, AMPS, and initiator were 0.80 mol%, 10 mol%, and 0.40 wt%, respectively; the pH was 8.0; and an ultrasonic power was 140 W. As the concentration of USPAM increased, the hydrophobic self-assembly behavior of USPAM caused its apparent viscosity and the amount of crosslinking in its structure to increase. The critical association concentration (CAC) was observed to be near to 0.38 g dl−1. Salt resistance appeared when the concentration of the USPAM solution exceeded 0.20 g dl−1. A maximum value of the apparent viscosity of USPAM solution was seen as the temperature was increased due to the enhanced self-assembly properties of the molecules. The addition of SDS improved the self-assembly behavior of USPAM below the CAC, but degraded this behavior above the CAC. The shape factor (<R g>/<R h>) tended to continuously increase. The aggregation number (N) presented a minimum value in the USPAM-SDS system.