pH sensitive smart gels of cetylpyridinium chloride in binary solvent mixtures: phase behaviour, structure and composition

Abstract

Cetylpyridinium chloride (CPC) gels from binary solvent mixtures of chlorinated solvents in the presence of water at a specific composition ratio have been studied. A transparent gel has been formed from CPC with dichloromethane, while a turbid gel with chloroform and a very weak opaque gel with carbon tetrachloride were observed in the presence of water. The CPC gel in a binary solvent mixture at a critical solvent composition of 3 : 1 v/v CHCl₃ : H₂O has been investigated as a function of pH between 4.1–11.8. The self-assembly of CPC and its morphology was found to be dependent on the solvent polarity/dielectric constant and pH of the medium. The absorption and emission characteristics of the CPC gel showed a significant response in a highly alkaline medium. The microstructure of the CPC gels in various chlorinated solvent combinations was proposed based on spectroscopic and microscopic investigations.