Effects of graphite oxide on thermal and electrical behaviors of coumarin-based methacrylate copolymers: Its single chain polymer molecule via intramolecular cyclobutane formation

Abstract

The random copolymers of methyl methacrylate (MMA) and 4-methyl-2-oxo-2H-chromen-7-yl methacrylate (COUMA) [poly (COUMA0.49-co-MMA)] (COMCOP1) and [poly(COUMA0.36-co-MMA)] (COMCOP2) were prepared via the conventional radical polymerization method. The copolymers were characterized by H-1-NMR, Fourier-transform infrared spectroscopy (FT-IR), UV-visible (UV-vis), thermogravimetric analysis, and differential scanning calorimetry instruments. A kinetic study of the thermal decomposition of COMCOP1 and COMCOP1/GO 16 wt% was investigated using thermogravimetric analyzer with non-isothermal methods selected for analyzing solid-state kinetics data. The average activation energy values were calculated via Flynn Wall and Ozawa (FWO) and Kissinger-Akahira-Sunose models in a period of alpha = 0.10-0.70. The average values of activation energy obtained from Kissinger method for COMCOP1 and COMCOP1/GO 16 wt% were 94.5 and 78.4 kJ/mol, respectively, whereas, those of estimated by FWO method were 103.5 and 87.0 kJ/mol. We indicate that well-defined single chain polymer molecule (SCPM) via intramolecular cyclobutane formation could be obtained by the intrachain photodimerization of coumarin groups during UV irradiation at 365 nm diluted solution of COMCOP1. The photodimerization of coumarin groups in the copolymer was confirmed by UV-vis, FT-IR, and H-1-NMR instruments. Dielectric and electrical behaviors of the composites having a semiconductor behavior filled GO were investigated. The activation energy values based on dc conductivity for COMCOP1 loaded GO 10 and 12 wt% were decreased from 0.206 to 0.069 eV. Also, the E-a values estimated for COMCOP2-loaded GO 12 and 13.6 wt% were 0.0580 and 0.0859 eV, respectively.