Self-assembly properties of hydrophobically associating perfluorinated polyacrylamide in dilute and semi-dilute solutions

Abstract

Hydrophobically associating perfluorinated polyacrylamide (HACFP) is a kind of novel cationic polyacrylamide prepared with acrylamide (AM), methacryloxyethyl trimethylammonium chloride (DMC) and 2-(perfluorohexyl)ethyl acrylate (FHA) through radical micellar polymerization. Macroscopic and microscopic self-assembly associative properties in solutions of HACFP as well as the effects of salt, temperature and shearing on the associative behavior were studied via viscosimetry, rheology, fluorescence spectroscopy (FS) and dynamic light scattering (DLS). Results showed that the critical association concentration (CAC) was ~0.24 wt.%, as determined via apparent viscometry and FS. The mixed hydrophobic macro-domains, which can be indicated by a change in I1/I3 FS values, and their associating behavior had apparent effects on the apparent average aggregate size (d*) observed by DLS. Also, incorporation of FHA endowed polyacrylamide with strong salt, heat and shearing resistance because of the intra- and inter-molecular hydrophobically associating aggregates which lead to a dynamic physical cross-linking network in its structure. The maximum apparent viscosity occurred when the polarity of the solution was enhanced in salt solution and the polymer coils were expanded with increased temperature.