This study reports the synthesis, characterization, and gas sensing applications of the PDPA-b-PDMA-b-PDPA triblock copolymer material using NMR, UV-visible spectroscopy, atomic force microscopy (AFM), quartz crystal microbalance (QCM), and Langmuir-Blodgett (LB) thin film deposition techniques. The thin film deposition conditions of the copolymer material, which are prepared by LB film technique, are characterized by UV-visible spectroscopy, AFM, and QCM system. In this study, the swelling behaviors of the PDPA-b-PDMA-b-PDPA triblock copolymer Langmuir-Blodgett (LB) films were investigated with respect to volatile organic compounds (VOCs) at room temperature. The sensing responses of the films against VOCs were measured by QCM method. The swelling processes could be investigated using the early-time Fick's law of diffusion.