Design, synthesis, and evaluation of nontoxic, biodegradable glycerol-based polycarbonates as novel biomaterials
Synthetic polymers intended for use in biomedical applications require the additional criteria of biocompatibility and sometimes biodegradability included within the design parameters along with mechanical properties, manufacturability, and other properties depending on the specific application in mind. The composition of the monomer and the type of linker within the main chain polymer as well as the chemical reactivity of these chemical entities will define the degradation rates and the conditions under which degradation will or will not occur. However, biocompatibility is usually a built-in characteristic related to the polymer (and monomer) composition and is not easily engineered into an existing polymer by conversion from a non-biocompatible to a biocompatible polymer. Consequently, a majority of the biocompatible polymers used in medical devices or evaluated for biomedical uses are composed of substances that are natural metabolites or known to be biocompatible and nontoxic. Using this design principle, a number of successful examples of biocompatible polymers have been reported such as poly(lactic acid), poly(glycolic acid), and their copolymers, and today, all of these polymers are used in US and EU approved devices. For similar reasons, glycerol-based polymers are attracting increasingly more attention for both fundamental studies and practical applications. Various glycerol polymer architectures from linear to dendritic have been reported for pure polyglycerol ethers and carbonates as well as copolymers with hydroxyacids, for example, to give polyether esters or polycarbonate esters. Herein, the design and synthesis of glycerol-based polycarbonates via copolymerization of epoxide and carbon dioxide is described. The underlying chemistry that affords these glycerol-based polycarbonates will be discussed. Their structural characteristics, their chemical, physical, and rheological properties, and as well as their applications with a focus on drug carrier will also be covered.