Structure and Biocompatibility of Bioabsorbable Nanocomposites of Aliphatic-Aromatic Copolyester and Cellulose Nanocrystals

Poly(butylene adipate-co-terephthalate) (PBAT) was first chemically modified via free radical grafting with maleic anhydride (MA) and the MA-g-PBAT graft copolymer was then used as a matrix material to obtain cellulose nanocrystal (CNC)-reinforced MA-g-PBAT bionanocomposites via reactive extrusion process to accelerate efforts to develop functional bioabsorbable polymer nano composites with improved properties. The molecular structure of the PBAT after chemical modification with maleic anhydride was confirmed by H-1 NMR and FTIR spectroscopy. The morphological observation of the nanocomposites revealed that the CNCs were finely dispersed in the matrix. Thermal analysis of the hybrids showed an improvement of the thermal stability of the nanocomposites upon increasing the CNC content. In addition, it was found that the CNC nucleated crystallization of the PBAT in the nanocomposites. Extensive melt rheological characterization of the nanocomposite samples revealed a significant improvement of the viscoelastic properties of the matrix due to the strong interfacial adhesion of the CNC particles to the PBAT. Further, development of the nonterminal characteristics of the viscoelastic material functions and exhibition of yield stress were correlated with the evolution of a 3D-netowork nanostructure of CNCs in the matrix. This CNC nanostructure was interpreted in the framework of scaling theory of fractal elastic gels, and found to be consistent with the structure of open-porous flocs. Tensile testing of the samples showed considerable improvement in the modulus and ultimate strength of the samples with increasing the CNC content. In addition, a positive shift of the glass transition temperature was found in dynamic mechanical analysis. Finally, in vitro biocompatibility using Thiazolyl blue tetrazolium bromide (MTT) assay and cell adhesion studies with L929 fibroblast cells revealed no cytotoxic effect of CNCs, confirming the biocompatibility of the nanocomposites and the associated significant improvement of cell adhesion, suggesting the potential applicability of this nanocomposite in biomedical and tissue engineering applications.