PEG-Grafted Graphene/PLLA Nanocomposites: Effect of PEG Chain Length on Crystallization Kinetics of PLLA.

Poly-l-lactic acid (PLLA) nanocomposites containing graphene oxide (GO), modified with different chain lengths of poly(ethylene glycol) (PEG) (400, 2000, and 10 000 g/mol), were prepared by solution casting. The effect of the PEG chain length and nanoparticle content (0.5, 1, and 1.5 wt %) on the nucleation, crystal growth rate, and overall crystallization rate, under isothermal conditions, was then evaluated. The results showed that, in samples containing GO modified with 400 g/mol of PEG, the nucleation density increased as a function of a modified nanoparticle concentration. In the case of the samples containing GO modified with PEG of a molar mass of either 2000 or 10 000 g/mol, the nucleation density exhibited a maximum at a concentration of 1 wt %. Furthermore, the addition of graphene oxide modified with poly(ethylene glycol) of a molar mass of 2000 g/mol resulted in the largest nucleation, fastest crystal growth, and highest overall crystallization rate, for all concentrations. The results were explained in light of the steric hindrance between the modified nanoparticles.