Study on the self-assembly properties of fluorinated hydrophobically associating polyacrylamide

Abstract

The self-assembly of a fluorinated hydrophobically associating polyacrylamide (UFPAM) prepared by emulsifier-free ultrasound-assisted radical polymerization was studied using fluorescence spectroscopy (FS), rheological measurements, and dynamic light scattering (DLS). The effects of the degree of mineralization (M), temperature, and the concentrations of ionic surfactants—sodium dodecyl sulfate (SDS) and cetyltrimethyl ammonium bromide (CTAB)—on the self-assembly behavior of UFPAM were explored in detail. The results showed that 2,2,3,4,4,4-hexafluorobutyl methacrylate (FA) was effectively incorporated into the UFPAM. As the concentration of UFPAM increased, the hydrophobic self-assembly behavior of UFPAM increased the apparent viscosity and enhanced the structural network of UFPAM, as indicated by the Ostwald–de Waele power-law model, FS, dynamic rheological measurements, and DLS. The maximum apparent viscosity of the UFPAM solution occurred when the polarity of the solution was enhanced in mineralized solution and the polymer coils were expanded at increased temperature. Provided that the concentration of the ionic surfactant was below its CMC, the addition of CTAB promoted the self-assembly of UFPAM, but this did not occur upon the addition of SDS. When the concentration of the surfactant was above the CMC, the aggregation number increased in the UFPAM–CTAB system, whereas it exhibited a minimum value in the UFPAM–SDS system.