Optical characterization and swelling behaviour of Langmuir-Blodgett thin films of a novel poly[(Styrene (ST)-co-Glycidyl Methacrylate (GMA)]

Abstract

In this study, FTIR, Raman, H-1-and C-13 NMR spectral studies, thermogravimetric analyses (TGA), UV-vis spectroscopy, atomic force microscopy (AFM), surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) measurements are used for copolymer characterization. A novel poly[(Styrene (ST)-co-Glycidyl Methacrylate (GMA)] is used to fabricate Langmuir-Blodgett (LB) thin films for the purpose of investigating its gas sensing properties. The thickness of this copolymer LB film, determined by the slope of the thickness versus layer number, is found to be 0.99 +/- 0.08 nm per monolayer. QCM and SPR systems are used to investigate gas sensing performance of copolymer LB films during exposure to Volatile Organic Compounds (VOCs). The changes in resonance frequency associated with mass changes can be attributed to the swelling behaviour of copolymeric thin films during vapor absorption. Fick's law for early-time diffusion was adopted to quantify real time QCM data for the swelling processes. It was observed that diffusion coefficients (D) for swelling obeyed the t(1/2)law and could be correlated with the VOCs used. The response of copolymer films to the chosen VOCs has been investigated, and the films were largely sensitive to dichloromethane vapor.