Studies on stereocomplex poly(lactic acid) and its biocomposites

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The current scenario of the world indicates that the consumption of plastics has constantly intensified and laid an impact on the society. However, the disposal of plastics is the prevailing issue of the world which has persuaded the researchers to develop alternatives for a sustainable future. Poly(lactic acid) (PLA) is a biobased plastic which can be considered as promising candidate for replacing petroleum based plastics such as polyethylene, polypropylene, polyethylene terephthalate, etc. PLA has been explored for its applications ranging from biomedical to textiles, agriculture, electronics, and packaging etc. but suffers from some drawbacks such as relatively low glass transition temperature, low heat deflection temperature, lower melting temperature, slow crystallization, lower melt elasticity and relatively poor gas barrier properties. Enhancing the properties of PLA is a major challenge and several methods such as fabricating biocomposite, polymer blending or formation of stereocomplex, etc. have been adopted by the researchers to improve the properties of PLA. PLA can be synthesized by polymerization of lactic acid or its derivative i.e. lactide. Lactic acid is a chiral molecule produced in the form of L-lactic acid, D-lactic acid or racemic lactic acid based on the fermentation reaction pathway. It is desired to produce high molecular weight PLA for several applications which is predominantly produced by ring opening polymerization (ROP) of lactide and the purity of lactide affects the molecular weight of the polymer. Mixing poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA) in different ratios, a specific type of polymorph called stereocomplex crystallite is formed which significantly enhances the melting temperature of PLA. Formation of stereocomplex crystallites are also responsible for the enhancement of barrier, mechanical and thermal properties. It has also been reported that low molecular weight PLLA and PDLA in 1:1 ratio can easily form stereocomplex crystallites.
Supervisor: Vimal Katiyar