Fullerene nanocomposites based on poly(lactic acid)

Full text: Fullerene was discovered in 1985 by Kroto et al [1]. This nanostructure has applications in optical limiters, photovoltaic cells, photodynamic therapy, antimicrobial activity and antiretroviral [2]. The aim of this study is to improve the interfacial interaction between fullerene and poly(lactic acid) for prepare a polymer nanocomposite. For this, fullerene C₆₀ was oxidized and modified with octadecylamine (ODA). Nanocomposites were prepared by solution casting using ultrasonic dispersion in chloroform (0,01% and 0,1% w/w). Nanocomposites were characterized by x-ray diffraction, thermal gravimetric analysis and differential scanning calorimetry. XRD exhibits that PLA 0,01% fullerene (ODA) has a structural ordering due the crystalline peak on this amorphous polymer. TGA results show that the presence of the nanostructured was capable of raising the heat resistance similarly for both concentrations because the initial degradation was 288 °C for PLA pure and 318 °C for nanocomposites. DSC of nanocomposites at lower concentration (0,01%) where there has been a glass transition temperature (T_g) of material displaced to a temperature higher than the pure matrix in 12 °C. Results of XRD was revealed that fullerene nanocomposite with lower concentrations presented a crystalline region. This fact contributes to justify the increase of T_g, as this sample showed a higher degree of organization and consequent increase in stiffness. The presence of fullerene in systems contributed to the increased stiffness of the respective nanocomposites, especially at lower concentrations evaluated, where there has been a T_g of material displaced to a higher temperature. This behavior reflects a better dispersion of the particles to 0.01%, with the biggest gain on interfacial area culminates in the most intense high rigidity of the PLA matrix. [1] H. W Kroto et al, Nature 318, 6042, 162-163 (1985) [2] Dos Santos et al, Química Nova, 33, 3, 680-693 (2010). (author)