Swelling behavior of the 2-(4-methoxyphenylamino)-2-oxoethyl methacrylate monomer LB thin film exposed to various organic vapors by quartz crystal microbalance technique

In this work FT-IR, H-1 and C-13-NMR spectra are used to analyze the structure of a novel 2-(4-methoxyphenylamino)-2-oxoethyl methacrylate (MPAEMA) materials. MPAEMA LB thin films are characterized by UV-Vis spectroscopy and Quartz Crystal Microbalance (QCM) techniques. The sensing behaviors of the films were investigated with respect to volatile organic compounds (VOCs) at room temperature. The sensing responses of the films against VOCs (dichloromethane, chloroform, benzene and toluene) were measured by the QCM method. It was found that the MPAEMA films exhibited good response, reversibility, stability and faster response and recovery characteristic to VOCs. The changes in resonance frequency associated with mass changes can be attributed to the swelling behavior of monomeric thin films during vapor absorption. This swelling is due to the capturing of organic vapor molecules in the sensor environment. 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 MPAEMA films to the chosen VOCs has been investigated in conditions of physical properties of the solvents, and the films were obtain to be largely sensitive to dichloromethane vapor compared to other studied vapors.