Making Epoxide-Based Biodegradable Polymers

Nowadays, synthetic polymers especially polyolefin have been widely used in our daily life. However, considering the nature that it can be hardly decomposed, it has caused serious environment problems. Polyester is a kind of biodegradable material which has been widely used in drug delivery systems and packing materials. Compared with the traditional condensation reaction of diols and diacids, prepare polyesters through copolymerization reaction of epoxides with anhydrides or lactones have attached much attention. However, the existing catalyst systems have some drawbacks such as low reactivity, poor selectivity and narrow substrates application. Based on the mechanism understanding of the copolymerization reaction, we believe that it's a kind of bimetallic cooperation mechanism. Therefore, this thesis developed dinuclear SalenCr(III)X complex to catalyze the copolymerization of various epoxides with cyclic anhydrides and 3,4-dihydrocoumarin(DHC), hoping to obtain epoxide-based polyesters with excellent properties.1. The dinuclear SalenCr(III)X complexes were employed for the copolymerization of epoxides and cyclic anhydrides. The influence of temperature, catalyst loading and etc. were investigated; the application of substrates was expanded to get functional polyesters. MALDI-TOF-MS shows that polyesters possess alternative structure. Using dinuclear SalenCr(III)NO3 as catalyst for SA/(5)-PO copolymerization, a highly regioregular ring-opening step was observed with a concomitant>95% retention of configuration at the methine carbon center of epoxide incorporated into the polyester. Moreover, DSC confirms that SA-COPO copolymer and PA-CHO copolymer possesses a high glass transition temperature (Tg) of 100? and 145 ?, respectively.2. The dinuclear SalenCr(III)X complexes were employed for the copolymerization of epoxides with 3,4-dihydrocoumarin(DHC), a kind of aromatic lactone. A series of aromatic polyesters were obtained with perfect alternative structure. DSC and XRD confirm that CHO-DHC copolymer, CPO-DHC copolymer and CBO-DHC copolymer are crystalline polyesters, possessing a melting point of 170?,138?and 111?, respectively; COPO-DHC copolymer is semi-crystalline polyester possessing a Tg of 52? and a melting point of 138?; CDO-DHC copolymer possesses a high Tg of 62.1?.