Studies on Development of Environmentally Benign Lactone based Polymers and their Composites for Biomedical Applications

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The current research work deals with various strategies to chemically connect the monomers (lactide and ε-caprolactone) at the molecular level and reduce the macrophase separation between them which is often witnessed when blending their respective polymers (PLA and PCL). This has been done by the random and block copolymerization techniques, where the block copolymerization (step ring opening polymerization) leads to the improved mechanical properties (strength, elongation, toughness and modulus) with the increasing block length of PLA. The diblock copolymers (PCL-PLA) and their stereocomplex blends are thermally processed by injection molding to form cortical and cancellous bone screws which are further tested for their thermomechanical stability at the sterilization temperature of biomedical devices. The linear triblock copolymers (PLA-PCL-PLA) result in the significant improvement in the mechanical properties as compared to the diblock copolymers. The triblock copolymer is thermally processed by twin-screw extruder to fabricate the filament followed by 3D printing to form a scaffold. The biocompatibility of the block copolymers is ascertained by performing MTT assay using human/rat bone osteosarcoma cells. Preferential formation of stereocomplexation is achieved upon synthesizing stereoblock terpolymers of PLA and PCL. Further, random copolymerization of L-lactide and ε-caprolactone (single step) leads to the development of copolymers which are chemically mixed (giving rise to a single Tg) and varying the content of caproyl and lactyl segments provide the range of materials with variable mechanical properties. Random copolymerization turns out to be an effective strategy for developing thermoresponsive copolymers and/or elastomeric materials. The random copolymer of L-lactide and ε-caprolactone is reinforced with bioglass (upto 50%) by solution casting method. The composites are characterized to determine their mechanical and thermal
Supervisor: Katiyar, Vimal