Smart borax complexes starting from anionic surfactant in association with unlabeled or fluorescently labeled poly(acrylic acid)s

Abstract

In this study, we evaluated borax’s effect upon sodium dodecyl sulfate (SDS)–poly(acrylic acid) (PAA) complexes. Comparison was made by using both unmodified and fluorescently modified polymers. Also, the influence of sodium chloride on the polymer–surfactant association was followed. To this end, a poly(acrylic acid) with molecular weight of 25,000 was grafted with 2.4 % 1-naphthylmethylamine. Surface tension, conductivity, and steady-state and time-resolved fluorescence measurements were performed. By investigation of the adsorption ability at water/air interface and by conductivity, it was revealed that both naphthyl tag and borax reinforce the interaction between SDS molecules and polymer. The photophysical data (polarity index, excimer formation, and lifetime of fluorophores) give more insight about stable nanostructures of surfactant–polyelectrolyte with the same charge. At low pH as well as sodium chloride and SDS contents, the heterogeneous microdomains of surfactant molecules with segments of coiled polymer were formed. At high pH, H-bonding nanostructures between borax and both sulfate of surfactant and carboxyl groups of the macromolecular chain were revealed.