Synthesis And Properties Of Aromatic-Aliphatic Copolyester And Functional Polyester Catalyzed By Rare Earth Catalyst Via Polycondensation

Due to the environmental pollution with solid wastes of plastic materials, aromatic-aliphatic copolyesters combining biodegradability with good use properties are of great interest and could be economically important. On the other hand, special attention has also been paid to the preparation of biodegradable polyester bearing functional pendant groups. The availability of reactive groups along the chains is highly desirable for fine tuning the properties in order to carry drugs, to improve biocompatibility, to control the biodegradation rate and so on. In this dissertation, a series of rare earth compounds were synthesized and used as a single component catalyst for melt (co)polycondensation to prepare aromatic-aliphatic copolyesters and linear functional polyesters. The functional polyesters were modified through the reactivity of pendant functional groups. The resultant polymers have been characterized by GPC,1H NMR, DSC, TGA etc measurementsAromatic-aliphatic copolyester PBTA was synthesized via direct polycondensation from dimethyl terephthalate(DMT), adipic acid(AA) and 1,4-butanediol(BG) with feeding mole ratio of DMT:AA=50:50 in the presence of different rare earth catalysts. Among various neodymium compounds tested, neodymium stearate shows higher catalytic activity and prepared PBTA with weight-average molar mass of 6.01 x104 g/mol. The rare earth elements affect the catalytic activity and Dy[OOC(CH2)16CH3]3 has a little higher activity than other rare earth stearates. The microstructures, thermal and mechanical properties of PBTA were characterized and analyzed.Rare earth stearates were applied to the polycondensation of dimethyl terephthalate(DMT), adipic acid(AA) and 1,2-ethandiol(EG) to produce PETA copolyester. The apparent rate constant of transesterization decreased linearly and molecular weight of PETA increased at first and drop obviously with decreasing catalyst concentration.A series of PETA with various feeding mole ratio of DMT/AA (30/70 to 80/20) were synthesized in the presence of neodymium stearate. The molecular weight, microstructures such as number-average sequence lengths of ethylene adipate unit(SLEA) and ethylene terephthalate unit(SLET) and degree of randomness(R), thermal and mechanical properties, biodegradation rate in composting tests were measured, showing some relationship with the composition of the copolyester.Copolyester PETSU, PETA and PETSE were prepared from succinic acid(SUA), adipic acid(AA), sebacic acid (SEA) with DMT and EG respectively by neodymium stearate. The length of alkyl group of the aliphatic acid affects the properties and biodegradation rate of the resultant polymers obviously.Melt (co)polycondensation of succinic acid, substituent dicarboxylic acid such as tartaric acid, malic acid and unsaturated maleic acid with aliphatic diols were carried out with rare earth triflates(Ln(OTf)3) at mild condition(60-80℃) to synthesis functional polyesters having pendent hydroxyl groups or carbon-carbon double bond by one-pot. The content of functional group in the main chain of the polyester can be controlled by feeding mole ratio of succinic acid and functional monomer. Modifications of polyesters were successfully conducted via the reaction of pendent hydroxyl group with carbonyl chloride, carboxylic group or carbon-carbon double bond with mercapto group.