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 1 H‐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 1 H‐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. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 47581.