A simple reactive blending method for in situ grafting of a low molecular weight poly(ethylene glycol) (PEG) was introduced to improve the ductility of poly(lactic acid)
(PLA).
The acryl groups of PEGA monomers were successfully reacted with PLA chains to form graft copolymers, which was confirmed from the results of NMR spectra, FTIR spectra, and XRD patterns as well as solvent extraction.
The glass transition temperature (Tg) of the grafted PLA (PLEAs) significantly decreased by 24 C compared with that of PLA. Besides, the glass transition of the PLEAs was defused at a broad temperature range between 15 C and 56 C depending on the grafted PEGA amount.
The melting temperature was also slightly lowered from 169.6 C for PLA to 163.1 C for PLEA40.
Interestingly, the degree of crystallinity for PLEAs apparently increased compared with neat PLA even though the melting enthalpy was decreased by 36% for PLEA30.
The Young’s modulus was decreased 66% from 1.3 GPa to 0.4 GPa and the elongation at break was increased by 380% from 4.7% to 17.9%.
These results explain that the grafted PEG moieties obviously affected the mechanical ductility of the PLA and plasticized the PLA matrix.
The grafted PEG moieties also facilitate hydrolytic degradation especially when the PEGA content is above 20%.
In conclusion, glass transition temperature and mechanical flexibility as well as biodegradability can be optimized by in-situ reactive blending via controlling
the grafted PEG amount in PLEAs which are suitable for applications as flexible films in advanced biodegradable materials.