Molecular and material design of aliphatic polyesters with controlled biodegragradability

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Various aliphatic polyesters have been synthyesized as biodegradable polymers thus far. Their biodegradability has been known to depend largely on the crystallinity as well as on the crystal size and morphology. In this research, various biodegradable polyesters having life-controlled degradability are designed and synthesized by ring-opening polymerization of new monomers and by well-controlled direct polycondensation.For example, glycolate and malate units were introduced into poly (3-hydroxybutyric acid) (PHB) to enhace the hydrolyzability of PHB and to have wide options for the functionalization of PHB. 12-Hydroxystearic acid (12HSA unti was also incorporated into poly (L-lactic acid) (PLLA) by ring-opening copolymerization of L-lactide and cyclic dimer of 12HSA in order to attain a soft PLLA derivative. Copolymerization of L-lactic acid with mandelic acid was also conducted to obtain glassy biodegradable copolymer with high glass transition temperature and increase degradability. … More Block copolymers of PLLA and poly (oxyethylene) (PEG) were prepared by the ring-opening copolymerization of PEG and L-lactide and dispersed into water to obtain core-shell nanoparticles. From these particles, a specific band structure was formed by the crystallization of the helical PLLA blocks. Sol-gel transition was found to occur on mixing the disperisions of the enationmeric A-B-A triblock copolymers, PLLA-PEG-PLLA and PDLA-PEG-PDLA. This transition was driven by the stereo-complexation of the PLLA and PDLA chains. The core-sheath bicomponent fiber consisting of poly (glycolic acid) (PGA) and PLLA as the core and sheath, respectively, was processed by melt-spinning. The fiber showed higher degradability than the single PLLA fiber.Enzymatic degradation of poly (butylene succinate) (PBS) and its derivative, poly (butylene succinate-co-terephthalate) (PBST) was studied by using a lipase originated from Pseudomonas cepacia. PBS and PBST was biodegraded by exo-type and endo-type scission of ester linkage, respectively. Less