Adsorption of Poly(acrylic acid) onto Negatively Charged Polystyrene Sulfate Latex Particles by Means of Particle Tracking of Brownian Motion, Electrophoretic Mobility and Fourier Transform Infrared Spectroscopy

Abstract

The adsorption of poly(acrylic acid) (PAA5K) with negative charge on the highly negatively charged polystyrene sulfate latex (PSL) particles at various ionic strengths were investigated in the present study. The adsorption of PAA was promoted with high ionic strength while the driving forces were mainly controlled by the non-electrostatic interactions including hydrogen bondings, dipole–ions and dipole–dipole. The adsorbed layer thickness of PAA on PSL and electrophoretic mobility of PSL in the presence of PAA increased with increasing ionic strength. In case of adsorption of 5 ppm PAA, the adsorbed layer thickness increased slightly about 2 times corresponding with 41.3 to 80.4 nm while the electrophoretic mobility of PSL changed from –4.87 to –6.31 μm cm/(V s) with increasing 100 times of the ionic strength from 0.1 to 10 mM KCl. The change of surface functional groups of PSL after PAA adsorption was thoroughly determined by Fourier transform infrared (FTIR) spectroscopy. The distinction between the electrostatic and the non-electrostatic interaction which contributed to the adsorption of PAA on the PSL particles and the adsorbed polymer conformations at different salt concentrations was clearly clarified. We demonstrate that the adsorbed PAA conformations were more vertically swollen at the PSL solid–solution interface.