【作者】 徐颖；

【导师】 李速明；

【作者基本信息】 复旦大学 ， 材料物理与化学， 2009， 硕士

【摘要】 近三十年来,生物降解高分子在基础研究以及化学工业领域都是研究热点。多种脂肪族聚酯都具有良好的水解性质,降解产物对环境和生物体没有毒性,尤其是一些脂肪族聚酯的降解产物甚至能被人体分解后排出,在生物医用具有广阔的应用前景。目前,大量文献报道了聚己内酯(poly(ε-caprolactonde),PCL)及其共聚物在生物医用方面的研究成果。PCL不但具有良好的生物相容性、生物降解性能,还具有优异的药物通透性。在作为药物控释体系载体方面受到了广泛关注。生物材料的各种应用依赖于其特定的物理性质,如作为骨科材料必须具有高模量,则需要较高的分子量和特定的凝聚态结构,而如果作为药物缓释材料,降解周期是一个重要参数,分子量相对较低。由于PCL为疏水性高结晶度聚合物,其水解周期很长,一般为2-4年。使得PCL在药物控释载体中的应用受到很大限制。通过在PCL链段中引入亲水性PEG,能很大程度上克服PCL均聚物这一缺陷。共聚物的结晶行为对其降解性能有很大影响,所以PCL-PEG共聚物的分子量、热行为、凝聚态结构和形态等相关基础研究具有重要理论和实际意义,这也是本论文的主要研究内容。PCL-PEG的合成多采用各种金属或其化合物作为催化剂。本论文中,采用低毒性乳酸锌作为催化体系,以聚乙二醇为引发剂,合成制备了不同分子量、不同组分比的PCL-PEG二嵌段聚合物,研究其热力学行为、结晶结构和形貌等。在以往对PCL-PEG结晶行为的报道中,有些学者发现了某个特定组成的PCL-PEG球晶存在一种特殊的同心圆形态,但是对于该现象的报道还很不深入。本论文的工作主要涉及以下内容:(1)制备了PEG分子量为5000,2000,1000的三个PCL-PEG系列共聚物样品,研究了样品的基本热力学行为、微观形貌等。等温结晶研究中,采用Avrami方程分析晶体成核、生长的类型,并计算得到共聚物的结晶动力学参数。(2)研究了组分比对共聚物热力学以及结晶动力学的影响。重点分析了PCL晶体与PEG晶体共存的环境中,结晶的生长方式,对同心圆现象提出新的解释。在对组分比的影响进行研究时,还观察到了棒状晶形态,这种形态为晶体的一维生长。同时,共聚物的分子量对样品的晶体生长速率也有显著影响。所获得的PCL-PEG二嵌段共聚物在结构分析、受热过程中吸热放热行为以及结晶形态等方面的数据,为更好地研究该共聚物的制备、加工和应用提供了一些重要参数。更多还原

【Abstract】 During the past three decades,biodegradable polymers have attracted much interest in both basic research and chemical industry.Aliphatic polyesters such as polylactide（PLA）,polyglycolide（PGA） and poly（e-caprolactone）（PCL） present excellent degradation properties,with degradation by-products harmless to the environment and animal body.Up to now,a great deal of work has been reported on biomedical applications of PCL and its copolymers,in particular in the fields of controlled drug release and tissue engineering due to the outstanding biocompatibility,biodegradability and drug permeability All these applications strongly depend on the specific physical properties. For example,high molecular weight（MW） and highly condensed structure are required for higher-modulus PCL used as tissue engineering scaffolds,while drug delivery systems generally require amorphous copolymers of relatively low MW. Hydrolytic degradation of PCL proceeds very slowly as PCL is a highly crystalline andhydrophobic polymer.The total degradation time is about 2-4 years,which strongly limits its application as drug carrier.Introduction of hydrophilic chains such as poly（ethylene glycol）（PEG） is a means to enhance the degradability and hydrophilicity of the materials.The crystallization behavior and morphology greatly influence the degradation performance of polymers.In literature,researchers have reported on the crystallization of PCL-PEG diblock and triblock copolymers.A specific concentric circle of crystals was observed.However,the crystallization of PCL-PEG copolymers with various PEG and CL/EO ratios has not been investigated in detail,so far.This work aims at investigating the morphology and crystallization of PCL-PEG diblock copolymers,including the thermodynamics,crystallization kinetics, condensed structure,morphology,and the influence of MW.Three series of PCL-PEG copolymers with various CL/EO ratios from 0.2 to 3.0 were synthesized by ring opening polymerization ofε-caprolactone in the presence of monomethoxy PEG with molar masses of 5000,2000 and 1000,using low toxic Zn（LA）₂ as catalyst.The copolymers were characterized by using analytical techniques including NMR,DSC,WAXD,and SEC.The thermodynamics of isothermal crystallization,crystal structure,and morphology were investigated in detail. The main contents of our work are shown as follows.1.PCL-PEG copolymers with various molar masses of PEG and CL/EO ratios were synthesized and characterized.The basic thermal behaviors and morphologies were determined.Avrami equation was used to analyze nucleation and growth type, deducing the kinetic parameters of crystallization.2.The influences of molar mass of PEG and CL/EO ratio on the thermodynamics and kinetics of PCL crystallization were investigated.Explanation on concentric circle of crystals was given.In particular,rod-like crystals were observed as one dimensional growth.The molar mass has great influence on the growth rate.更多还原