AbstractThis study investigated the effect of oxygen plasma treatment on the glass transition temperature of enzymatic hydrolysis lignin (EHL) derived from the production of bio-ethanol. Differential scanning calorimetry (DSC) was used to obtain the glass transition temperature (Tg) of EHL. The results showed that the Tg value of EHL under different heating rates ranged from 160 to 200 °C, and there was a strong linear correlation between heating rate and Tg. The Tg value of oxygen plasma treated EHL decreased when compared with the untreated samples. The apparent Tg of the untreated sample was 168.2 °C, while the value of the treated sample was 161.5 °C. Distinct chain scission and introduction of oxygen-based functional groups on the surface of EHL were detected by XPS analysis. These changes may occur mainly on the bulky side chain and thus enhance molecular mobility of EHL. This indicates that oxygen plasma treatment can modify the structure and improve the reactivity of EHL efficiently.