Novel approach to promote the hydrophobic association: Introduction of short alkyl chains into hydrophobically associating polyelectrolytes

A novel approach to promote hydrophobic association by incorporating short alkyl chains onto polyelectrolytes (HAPEs) was presented. A series of HAPEs was synthesized by free radical copolymerization in aqueous media with acrylamide (AM), 11-acrylamidoundecanoic acid (C(11)AM), and 6-acrylamidohexanoic acid (C(6)AM). The structures and compositions of the polymers were confirmed by H-1-NMR, and the molecular weights were determined by GPC. Results of rheological experiments revealed that viscosities increased greatly in samples containing C(11)AM and C(6)AM compared with the sample without C(6)AM. The sample without C(6)AM was also characterized by critical association concentrations and critical angular frequencies. Solubilization and bridging interaction were considered as the possible reasons. Pyrene fluorescence probe data and H-1-NMR spin-spin relaxation times further illustrated the reinforcement of hydrophobic associations by short alkyl side chains. All the results showed that the optimum content of C(6)AM was 1 mol % in the prepared HAPEs. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47581.