Degradable Polycarbonate Networks Derived from Quinic Acid and Designed for Biomedical Applications
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The pursuit of polymers with natural and renewable precursors is driven by two specific aims: (i) to develop sustainable and biodegradable plastics which decrease dependence on petroleum feedstocks and address problems associated with plastic waste and pollution, and (ii) to design novel biomaterials with built-in biocompatibility and the ability to degrade under physiological conditions to produce resorbable natural byproducts. Herein, a new family of nontoxic bio-based polycarbonate networks that exhibit a wide range of achievable thermomechanical properties and have the potential to breakdown hydrolytically into biologically-beneficial and environmentally-benign degradation products is described. The natural product quinic acid, known for its antioxidant and growth-promoting properties, was selected as the monomeric building block, and hydrolytically labile carbonates were selected as the linkages. Solvent-free thiol-ene chemistry was utilized in the copolymerization of tris(alloc) quinic acid and a variety of multifunctional thiol monomers to obtain poly(thioether-co-carbonate) networks. Natural multifunctional thiols derived from lipoic acid, a metabolic antioxidant, were explored to further increase the overall natural content of the material. A wide range of tunable thermomechanical properties including glass transition temperatures from −18 to 65 °C and mechanical characteristics from a rubbery elastomer to a rigid plastic was achieved by careful selection of thiol monomers. Special attention was paid to the characterization of structure-thermomechanical property relationships and how these relationships change under physiological conditions. The short-term mechanical changes triggered by solvent plasticization in a physiologically-relevant environment (PBS, pH 7.4, 37 °C) were observed by submersion dynamic mechanical analysis. The long-term degradation kinetics, including swelling and mass loss, were monitored, and the results showed a range of degradation times from 5 to ~35 weeks based on the crosslink density and hydrophilicity of the polymer network. In vitro cytotoxicity and cell attachment studies were performed, and X-ray imaging contrast properties were observed to investigate the feasibility of the poly(thioether-co-carbonate) networks to serve as platform materials in biomedical applications, specifically as orthopedic implant devices. Overall, by using simple fabrication techniques and reliable chemistry, the poly(thioether-co-carbonate) networks developed in this work represent a versatile and nontoxic family of materials which may be used for to a wide variety of applications.
Link, Lauren A (2015). Degradable Polycarbonate Networks Derived from Quinic Acid and Designed for Biomedical Applications. Doctoral dissertation, Texas A & M University. Available electronically from