Study of thermomechanical, structural and antibacterial properties of poly(lactic acid) reinforced with graphene oxide nanoparticles via melt mixing

Addition of graphene oxide (GO) to poly(l-lactic acid) (PLLA) offers an alternative approach for tuning its crystallinity, improving its mechanical properties and transfusing an antibacterial behavior. GO/PLLA nanocomposites were prepared by melt extrusion, thus avoiding the potentially toxic, for biomedical applications, residue of organic solvents. Fourier transform infrared spectroscopy verified the formation of intermolecular hydrogen bonds. Using differential scanning calorimetry experiments concerning the isothermal crystallization of PLLA and PLLA containing 0.4 wt% GO, a two-dimensional disc-like geometry of crystal growth was determined, whereas at 125 and 130 degrees C the nanocomposite developed three-dimensional spherulitic growth. Higher crystallization rate constant values suggest that the incorporation of 0.4 wt% GO accelerated the crystallization of PLLA. The lowest crystallization half-time for PLLA was observed at 115 degrees C, while at 110 degrees C GO caused its highest decrease, accompanied by the highest increase in melting enthalpy (Delta H-m), as compared to that of PLLA, after completion of isothermal crystallization. Their Delta H(m)values increased withT(ic), whereas multiple melting peaks transited to a single one with increasingT(ic). GO improved the PLLA thermal stability, tensile strength and Young's modulus. Incorporation of 0.8 wt% GO endowed PLLA with another potential application as a biomaterial since the derived composite presented good thermomechanical properties and effective prohibition ofEscherichia colibacteria attachment and proliferation. This effect was more prominent under simulated sunlight exposure than in the dark. The preparation method did not compromise the intrinsic properties of GO. (c) 2020 Society of Chemical Industry