Thermo-oxidative degradation of ultrahigh molecular weight poly(ethylene oxide) in volatile organic solvents

The degradation of ultrahigh molecular weight poly(ethylene oxide) (UHMWPEO) was investigated in three volatile organic solvents, methanol, chloroform, and tetrahydrofuran. Particularly, degradation rate was determined by means of Ubbelohde viscometry and degradation products were characterized by using electron spin resonance spectroscopy (ESR) and Fourier transform infrared spectroscopy (FTIR). The highest degradation rate was observed for UHMWPEO in tetrahydrofuran, with the lowest one in methanol. The ESR results showed that PEO-C center dot and center dot OH radicals were produced during the degradation process. Among these selected solvents, tetrahydrofuran was found to generate free radicals through an autoxidation mechanism. This would accelerate the degradation of UHMWPEO, resulting in the observed highest degradation rate in the UHMWPEO/tetrahydrofuran solution. Esters were also detected in the degradation products of these UHMWPEO solutions, while formates and formate ions were generated in the solutions of UHMWPEO/tetrahydrofuran and UHMWPEO/cloroform except for PEO/methanol. Furthermore, the degradation mechanism of UHMWPEO was deduced. This work enabled an in-depth understanding on the thermo-oxidative degradation mechanism of UHMWPEO in representative organic solvents, which would be instructive for developing optimal solution-based processing technique of UHMWPEO.