Thermo- and pH-responsive behaviors of aqueous poly(acrylic acid)/poly(4-vinylpyridine) complex material characterized by ATR-FTIR and UV–Vis Spectroscopy

A novel thermo- and pH-responsive poly(acrylic acid) (PAA)/poly(4-vinylpyridine) (P4VP) aqueous material with an upper critical solution temperature (UCST) was developed in this study. It was found that the formation of the aqueous complex material was caused by the deprotonation of pyridinium groups of P4VP molecules and consequent hydrogen bonding formation between pyridine and carboxylic groups. This aqueous material exhibited significant reversible transition behaviors between the turbid colloidal and transparent solution states upon altering the pH and temperature values. Furthermore, the correlation between the solution pH and the upper critical solution temperature (UCST) enables us to design responsive aqueous materials with a broadly adjustable transition temperature range.