Stability of chitosan/montmorillonite nanohybrid towards enzymatic degradation on grafting with poly(lactic acid)

Enzymatic degradation of nanohybrid based on intercalation of chitosan (CS) within the galleries of montmorillonite (MMT) clay and grafted with poly(lactic acid) (PLA) was studied using esterase enzyme in phosphate buffered solution. Chitosan was first intercalated between the galleries of natural unmodified sodium MMT clay and subsequently grafted with PLA to prepare nanohybrids of CS-g-PLA/MMT. The prepared membranes were characterised by X-ray diffraction, transmission electron microscopy and NMR spectroscopy. The specimens were then subjected to enzymatic degradation to understand the effect of copolymerisation with PLA and the effect of incorporation of MMT in the CS matrix. The presence of MMT clay provided stability towards degradation of polymer matrix because of nanoscale dispersibility, thereby acting as a barrier towards the permeation of water molecules to induce hydrolysis of PLA. Similarly, the grafting of CS with crystalline PLA stabilised the CS matrix towards degradation, rendering it suitable for tissue engineering applications.