Effect of molecular weight of poly(acrylic acid) on the interaction of oppositely charged ionic surfactant–polyelectrolyte mixtures
Journal
Journal of the Taiwan Institute of Chemical Engineers
Journal Volume
92
Pages
50-57
Date Issued
2018
Author(s)
Abstract
The isothermal titration calorimetry was applied to investigate the effect of molecular weight (MW) of poly(acrylic acid) (PAA) on the interaction of tetradecyltrimethyl ammonium bromide (C14TAB) with PAA in the bulk phase. The initial formation of PAA/C14TAB complexes was driven by electrostatic interactions between the cationic head groups of C14TAB and the oppositely charged PAA chains, resulting in enhanced hydrophobicity of the complexes. The further addition of C14TAB would induce either complex-C14TAB interaction or complex–complex interaction due to hydrophobic effect. Increasing the MW of PAA would enhance the tendency of complex–complex interaction to form aggregation and even precipitation. For PAA MW ≥ 130,000, significant precipitation of interpolymer complexes was consistently observed and all the obtained critical micelle concentration, phase separation concentration, heat of complexation, and heat of micellization were independent of MW. For PAA MW of 25,000, the complexes formed visible millimetric aggregates at phase separation concentration. With further addition of C14TAB, these aggregates gradually dissolved, and the solution became clear again. For PAA at an MW of ≤5000, turbidity was observed in a wide range of concentrations, but no macroscopic precipitation was observed and the solutions were always homogeneous.
SDGs
Type
journal article