Poly (L-lactic acid)/layered silicate nanocomposite: Fabrication, characterization, and properties

The possibility of making rigid polymer layered nanocomposites from biocompatible/ biodegradable matrixes was explored. Three types of commercially available organophilic clay were employed to concurrently study the effects of organic modifier miscibility with the matrix and of the extent of clay modification on overall nanocomposite formation. The nanocomposites were fabricated via the exfoliation-adsorption technique with the matrix polymer poly (L-lactic acid), PLLA, a widely used, biodegradable, synthetic polyester. X-ray diffraction (XRD) data reveal that increasing the miscibility of the surfactant/polymer matrix increases the tendency of the system to exfoliate and randomly distribute the silicate layers. Transmission electron microscopy (TEM) data show that the ordering of silicate platelets is consistent with d spacings obtained from XRD. Because of the nanometer-range dispersion of silicate layers, all the nanocomposites retain their optical clarity. Mechanical properties of the fabricated nanocomposites were probed by dynamic mechanical analysis and show significant improvements in the storage modulus when compared to neat PLLA. The extent of crystallinity was observed to be inversely proportional to the extent of modified clay loading in the final composites.