Investigating the effect of weak polyelectrolytes on the chemical stability and swelling recovery of multilayered coatings

Abstract

The purpose of this article is to investigate the stability of multilayered coatings composed of chitosan, poly(sodium 4-styrene sulfonate) and poly(acrylic acid) against various salt solutions using Quartz Crystal Microbalance-Dissipation (QCM-D) and analyze the effects of salt concentration, upper layer charge type and multilayer structure. The study also examines the impact of methanol and heptane on the swelling behavior of the multilayers. The results show that chitosan-poly(acrylic acid)-based coatings remained mostly stable against salt solutions and solvents, except for 1 M sodium hypochlorite, while 5 bilayered chitosan-poly(sodium 4-styrene sulfonate) completely decomposed to initial polyelectrolytes against 1 M magnesium chloride and sodium hypochlorite. The multilayer stabilities of coatings do not change depending on the surface charge type while some changes occur in adsorbed and desorbed amounts during the salt passage and rinsing steps. Chitosan-based coatings exhibit a greater mass loss percentage and change in dissipation against 1 M magnesium chloride than sodium chloride-treated multilayers because of the high ionic strength of magnesium chloride solution. The multilayered coatings with poly(acrylic acid) showed larger changes in dissipation values and reversibility in swelling. This behavior can be useful for shape memory coatings and drug delivery platforms of Layer-by-Layer assembled multilayers.