Poly(methyl methacrylate) copolymers containing dipyrrolylquinoxaline receptors for the colorimetric detection of halide anion salts

Abstract

Described herein is the synthesis of a dipyrrolylquinoxaline (DPQ) monomeric species containing methacrylamide functionality, and its subsequent copolymerisation with methyl methacrylate (MMA). The resulting copolymers were drop casted onto glass substrates, and the resulting thin films displayed distinct colorimetric change upon exposure to hydrofluoric acid (HF) vapour. Furthermore, glass substrates coated with the DPQ-MMA copolymer could be used as 'dip sticks' to test for trace acid in solution, turning from yellow to red upon immersion in an aqueous solution of HF. Analysis by UV-vis spectroscopic titration allowed the association constant (K-a) for interaction with fluoride (as the tetrabutylammonium salt) to be calculated as 6.16 x 10(5) M-1 in CH2Cl2. Polymer coatings of this type could find applications in the colorimetric detection of HF vapour, a common hazard associated with industrial processes, such as aluminium smelting.