【作者】 李凤红；

【导师】 张宝砚；

【作者基本信息】 东北大学 ， 材料学， 2008， 博士

【摘要】 壳寡糖是一种来源丰富的天然高分子,它具有良好的生物相容性、生物降解性和生物活性。但是由于分子间的氢键相互作用,使其具有难融难溶的性质,因而大大限制了壳寡糖这一天然资源的有效利用。化学改性是改善壳寡糖性能的有效途径,特别是利用良好亲水性及带有生物活性基团的壳寡糖和具有优越机械性能及生物降解性的聚己内酯、以及含生物活性物质胆甾醇的液晶单体,制备的新型壳寡糖基生物材料,具有重要的科学参考价值和巨大的应用前景。将在生物降解材料、药物控释载体和组织工程材料方面获得应用。本论文是在查阅了国内外大量相关文献的基础上,为了改善壳寡糖溶解性差、不能熔融、不具备成型加工性能的缺点,对壳寡糖的-NH2或-OH进行化学改性,设计并合成了两种壳寡糖衍生物中间体及四种壳寡糖基生物材料。两种中间体是：邻苯二甲酰化壳寡糖(PHCSO)和O,O-双十二酰化壳寡糖。四种壳寡糖基生物材料分别是：1.热塑性N,O酰化壳寡糖；2.含活性氨基的邻苯二甲酰化壳寡糖接枝聚己内酯；3.热塑性壳寡糖接枝聚己内酯；4.胆甾醇酯支化的壳寡糖接枝聚己内酯。文中所设计并合成的壳寡糖基生物材料在国内外未见报道,研究成果具有创新性。采用FT-IR、1H NMR、DSC、TGA、POM、SEM及X射线衍射等技术研究了壳寡糖基生物材料的化学结构和物理性能。主要内容和研究成果如下：1.对壳寡糖进行酰化改性,即在甲烷磺酸的均相反应体系中,通过甲烷磺酸对壳寡糖氨基的保护作用,采用月桂酰氯直接与壳寡糖的羟基反应,制备了羟基(-OH)被取代而保留活性氨基的O,O-双十二酰化壳寡糖。O,O-双十二酰化壳寡糖在有机溶剂中的溶解性得到改善,SEM表明壳寡糖的片层结构发生变化,且表面变得粗糙,XRD和热分析表明月桂酸基长链的引入改变了壳寡糖分子的结构,酰化壳寡糖形成了新的结晶结构,O,O-双十二酰化壳寡糖的热降解温度低于壳寡糖。2.在合成了O,O-双十二酰化壳寡糖的基础上,又通过改变月桂酰氯与壳寡糖的摩尔比使壳寡糖分子结构中的氨基(-NH2)也参与了反应,从而制备了取代度不同的N,O-双十二酰化壳寡糖,研究结果表明月桂酸基长链的引入削弱了壳寡糖分子间的氢键作用力,改变了壳寡糖分子的结构,酰化壳寡糖形成了新的结晶微区；当壳寡糖的氨基和羟基几乎被完全取代时,N,O-双十二酰化壳寡糖具有热塑性,其热降解温度为167.3℃,而且在偏光显微镜下能够观察到颗粒状紧密排列的结晶结构。3.通过邻苯二甲酸酐保护壳寡糖的氨基,而保留羟基制备了反应中间体邻苯二甲酰化壳寡糖(N-phthaloyl-chitosan oligosaccharide,简称PHCSO)。在壳寡糖的接枝反应中以邻苯二甲酰化壳寡糖为中间体,采用辛酸亚锡催化剂催化ε-己内酯开环聚合制备了邻苯二甲酰化壳寡糖接枝聚己内酯(PHCSO-g-PCL),这种接枝反应路线可实施壳寡糖的定位接枝改性。另外,采用水和肼脱掉了N-邻苯二甲酰亚胺基保护基从而恢复了壳寡糖的游离氨基。结果表明随着ε-己内酯(ε-CL)与壳寡糖投料比的增加,接枝率提高,并且壳寡糖分子的结晶结构被破坏,侧链聚己内酯在接枝共聚物中已形成了新的结晶区,该结晶区具有熔点。4.以PHCSO为中间体,采用辛酸亚锡催化剂催化ε-己内酯开环聚合,当ε-己内酯与邻苯二甲酰化壳寡糖的配比为15：1(mL/g)时,制备了热塑性壳寡糖接枝聚己内酯复合材料(TPHCSO-g-PCL)。TGA、WAXD、SEM、DSC用来表征壳寡糖-接枝-聚己内酯的物理性能,表征结果表明聚己内酯在壳寡糖上的接枝在一定程度上破坏了壳寡糖原有的结晶形态,聚己内酯接枝侧链在壳寡糖的刚性骨架上已经形成大量的结晶区。壳寡糖、均聚物聚己内酯(PCL)及热塑性接枝共聚物在热失重为5%时的温度分别为205℃、224℃和252℃。TGA分析结果表明热塑性接枝共聚物的热稳定性均高于壳寡糖和PCL。在偏光显微镜(POM)下观察到TPHCSO-g-PCL的球晶结构。DSC曲线表明TPHCSO-g-PCL的熔点为60.2℃。5.以PHCSO-g-PCL为中间体,通过壳寡糖接枝聚己内酯(PHCSO-g-PCL)上的羟基与己二酸胆甾醇单酯(M1)或癸二酸胆甾醇单酯(M2)的羧基进行酰化成酯反应,合成了胆甾醇酯支化的壳寡糖接枝聚己内酯复合材料(PHCSO-g-PCL-g-Chol*,n=4,8)。其中癸二酸胆甾醇单酯支化的壳寡糖接枝聚己内酯复合材料(PHCSO-g-PCL-g-Chol*,n=8)具有热塑性,在偏光显微镜下(POM)能够观察到M1和M2的胆甾相液晶织构、PHCSO-g-PCL-g-Chol*(n=8)在熔融时出现的双折射现象,该热塑性材料在DSC曲线上的熔融峰的峰值为89℃。更多还原

【Abstract】 Chitosan oligosaccharide is a well-known abundant natural polymer with good biodegradability, biocompatibility and bioactivity. But the insolubility in common organic solvents and non-thermal plasticity of chitosan oligosaccharide have delayed its utilization and basic research. Chemical modification of chitosan oligosaccharide is more attractive to expand the applications as functional materials. Especially, it is promising and have great value of scientific reference to combine the chitosan oligosaccharide (CSO) having good hydrophilic property and bioactive functions with poly (ε-caprolactone) which has good mechanical properties and biodegradability, and liquid crystal monomers having bioactive cholesterol to generate new biomaterials based on chitosan oligosaccharide. These materials should be applicable for biodegradable material, drug delivery systems and tissue engineering.On the base of large related information retrieval research at home and abroad, in this dissertation, we have designed and synthesized two kinds of precursors of chitosan oligosaccharide derivatives, four kinds of biomaterials based on chitosan oligosaccharide through the modification of amino groups and hydroxyl groups of CSO. The purpose of it is to improve its poor solubility in organic solvents and the limits of non-processability because it has no melting point. Two kinds of precursors are phthaloyl chitosan oligosaccharide (PHCSO) and O,O-dilauroyl chitosan oligosaccharide (LCSO), respectively. Four kinds of biomaterials based on CSO are thermoplastic N,O-dilauroyl chitosan oligosaccharide (NOCSO-2), chitosan oligosaccharide-graft-poly (ε-caprolactone) with free active amino groups, thermoplastic phthaloyl chitosan oligosaccharide-g-polycaprolactone, and phthaloyl chitosan oligosaccharide-g-polycaprolactone-g-cholesterol respectively. As far as we know, the designed biomaterials based on chitosan oligosaccharide have never been reported, they are innovative. The chemical structure and physical properties of biomaterials based on chitosan oligosaccharide are confirmed by fourier transform infrared (FT-IR) spectra、1H nuclear magnetic resonance, differential scanning calorimetry (DSC), thermogravimetric analyse (TGA), polarizing optical microscopy (POM), scanning electron microscope (SEM), X-ray diffraction (XRD). The main contents and results list below:1. Through acylation modification of chitosan oligosaccharide, O,O-dilauroyl chitosan oligosaccharide (LCSO) was synthesized by the reaction of the hydroxyl group of chitosan oligosaccharide (CSO) and suitable count of lauroyl chloride via the amino groups protection procedure in homogeneous system of methane sulfonic acid. The solubility of LCSO had been improved in organic solvents. SEM indicated that the layer structure of CSO has been changed and the surface morphology of LCSO became crude. XRD and themoanalyses indicated that the original crystal structure of CSO did change with the lauroyl acylations and had created new crystal domains of lauroyl side chains. The decomposition temperature of LCSO is lower than that of CSO.2. On the basis of LCSO, N,O-dilauroyl chitosan oligosaccharide (NOCSO) with different substitution were synthesized through changing the mole ratio of lauroyl chloride to chitosan oligosaccharide to make the further reaction of amino group. The results showed that the intra hydrogen bonding of CSO was weakened and the original crystal structure of CSO did change through the introduction of long lauroyl side chains and had created new crystal domain of lauroyl side chains. When almost all the amino group and hydroxyl group were substituted, NOCSO has thermoplasticity and the decomposition temperature is 167.3℃. The grain structure aligned tightly and can be observed by POM.3. Phthaloyl chitosan oligosaccharide precursor (PHCSO) was synthesized via the amino groups protection of CSO with phthalic anhydride. The phthaloyl chitosan oligosaccharide-g-polycaprolactone (PHCSO-g-PCL) was synthesized by coupling the hydroxyl group via the ring-opening graft copolymerization ofε-caprolactone in the presence of stannous octoate catalyst. The regioselective graft modification of CSO can be done through this method of graft polymerization, and the free amino group can be abstained through removing the protective group by hydrazine. It was found that the graft content of PCL within the graft copolymer increased with the increasing of the mole ratio ofε-caprolactone to phthaloyl chitosan oligosaccharide. Besides, new crystal domains of polycaprolactone side chains occurred and had melting endothermic peak of PCL in PHCSO-g-PCL while the crystal structure of CSO was damaged.4. The thermoplastic chitosan oligosaccharide-g-polycaprolactone composite (TPHCSO-g-PCL) were successfully synthesized via ring-opening polymerization ofε-caprolactone (ε-CL) using phthaloyl-chitosan as intermediate while the feed ratio ofε-caprolactone to phthaloyl chitosan oligosaccharide precursor (PHCSO) is 15:1 (mL/g). The physical properties of the graft copolymers were characterized by TGA, WAXD, SEM and DSC, respectively. The results showed that the original structure of CSO was changed to some extent by the grafting of PCL to the backbone of CSO. The temperature at 5% weight loss of CSO, pure PCL and PHCSO-g-PCL are 205℃,224℃and 252℃, respectively. TGA analysis showed that TPHCSO-g-PCL was more thermal stable than original CSO. Spherulite morphology of this material can be observed by POM. The melting point of TPHCSO-g-PCL is 60.2℃.5. PHCSO-g-PCL-g-Chol* (n=4,8) was synthesized by coupling the hydroxyl group of PHCSO-g-PCL with the carboxyl of single hexanedioic acid cholesterol ester (M1) or single sebacic cholesterol ester (M2) via acylation reaction. PHCSO-g-PCL-g-Chol* (n=8) has thermoplasticity. The cholesteric liquid crystal texture of M1, M2 and the birefringence phenomeon of PHCSO-g-PCL-g-Chol* (n=8) during the melting process was observed by POM. DSC curve showed that PHCSO-g-PCL-g-Chol* (n=8) has maximum melting endothermic peak at 89℃.更多还原