Thin Polymeric Films for Real-Time Colorimetric Detection of Hydrazine Vapor with Parts-per-Million Sensitivity

Thin colorimetric films based on polymers have received considerable attention because of their simplicity and cost-effectiveness in the sensing of hazardous gaseous substances. Here, thin polymeric films were prepared and used for the vapor-phase colorimetric detection of a hazardous hydrazine with high sensitivity. Photo-cross-linkable poly(N,N-dimethylacrylamide-co-azo-dicyano-co-N-(4-benzoylphenyl)acrylamide), p(DMA-co-M1-co-BPAm), hereafter referred to as P1, was used to create a polymeric film for tracing hydrazine vapor with real-time applicability. P1 was synthesized by postmodification of poly(DMA-co-FPDEA-co-BPAm), which was copolymerized via free radical polymerization of N,N-dimethylacrylamide (DMA), (E)-2-((4-((4-formylphenyl)diazenyl)phenyl)(methyl)amino) ethyl acrylate (FPDEA), and N-(4-benzoylphenyl)acrylamide) (BPAm). P1 displayed selective sensing properties toward hydrazine in tetrahydrofuran and semiaqueous media. The apparent color of P1 changed from red to yellow (a ∼69 nm blue shift) because of the hydrazine attack on the α-position of the dicyano group of M1, resulting in inhibition of the intramolecular charge transfer process. The heterogeneous film, F1, was prepared by the ultraviolet irradiation of spin-coated P1 on a quartz substrate. Amounts of hydrazine vapor as low as 10 parts-per-million were detectable by F1. The successful colorimetric detection of hydrazine was also achieved in various media, including different types of soil and water, demonstrating the potential of the system for various practical applications.