Salt stimulus response of a carboxyl betaine amphoteric hydrophobic associative polyacrylamide

Abstract

A carboxyl betaine amphoteric hydrophobic associative polyacrylamide (CBAHAPAM) was synthesized in water solution through radical polymerization, which was made of polyacrylamide, N,N′-dimethyl octadecyl allyl ammonium chloride (DOAC), 1-carboxy-N,N′-dimethyl-N-(3-methylacryl-amidopropyl) ethanaminium inner salt (CBMAA-1) and 2-acrylamide-2-methyl propanesulfonic acid (AMPS). Self-assembly associative properties in CBAHAPAM solution and the effects of salt and temperature on the associative behavior were investigated by the means of viscosimetry, rheological test, fluorescence spectroscopy, and environmental scanning electron microscope (ESEM). Results showed that the critical association concentration (CAC) of the CBAHAPAM was about 0.30–0.32 wt %. The addition of the calcium chloride made the apparent viscosity of CBAHAPAM solution improve drastically than NaCl. Meanwhile, CBAHAPAM solution with NaCl and CaCl₂ showed up better heat and shearing resistance than CBAHAPAM solution itself. The network structures of CBAHAPAM aqueous or salt solution was observed by ESEM. NaCl and CaCl₂ reinforced the network structures, which further indicated that CBAHAPAM solution had a excellent capacity of salt thickening.