Free volume can control biodegradation rate of polylactic acid

We evaluated whether the enzymatic degradation rate of biodegradable plastics is related to the amorphous structure of the polymer. The free-volume, meaning the cavity between the polymer chains in the amorphous part, is known to influence various physical properties. In this study, enzymatic degradation tests were performed on polylactic acid (PLA) films with free-volume hole sizes estimated by positron annihilation lifetime spectroscopy (PALS). Films with different free-volume hole sizes near the surface region degraded in different modes, and a positive correlation, with a correlation coefficient of 0.713, was observed between the degradation rate in the initial 30 min and the free volume size near the surface. These results suggest the possibility of controlling the degradation rate of the amorphous region by controlling the free volume size, which is important for future applications of biodegradable plastics in a wide range of fields.

Automated summary

This study evaluated the relationship between the enzymatic degradation rate of biodegradable plastics and the amorphous structure of the polymer. The free-volume of the amorphous part, which refers to the cavity between the polymer chains, is known to impact various physical properties. Enzymatic degradation tests were conducted on polylactic acid (PLA) films with different free-volume hole sizes estimated by positron annihilation lifetime spectroscopy (PALS). The results showed that films with different free-volume hole sizes near the surface region degraded in different modes, and there was a positive correlation (correlation coefficient: 0.713) between the degradation rate in the initial 30 minutes and the free volume size near the surface. These findings suggest that controlling the free volume size can control the degradation rate of the amorphous region, which is significant for the future applications of biodegradable plastics in various fields.