【作者】 李素文；

【导师】 王庭慰；

【作者基本信息】 南京工业大学 ， 材料学， 2004， 硕士

【摘要】 聚氨基酸是一种低毒、生物降解性和生物相容性好、容易被机体吸收、代谢的生物降解高分子,它的应用非常广泛,如在医学领域中用于药物控释、人造皮肤等方面。但聚氨基酸的应用跟其分子质量有着密切的关系,合成聚氨基酸方法虽多,大多数氨基酸只能通过氨基酸 N-羧酸酐(N-Carboxyl-α-amino acidAnhydride 简称 NCAs) 法才能得到高分子质量的聚氨基酸。目前报道较多主要是聚谷氨酸、聚天冬氨酸和聚亮氨酸等,而作为丝蛋白中最主要的聚丙氨酸在这方面的研究甚少。本文以 L-丙氨酸(L-Alanine)为对象,系统的研究了 NCAs的合成以及 L-Ala-NCAs 开环聚合反应中引发剂、溶剂、温度、时间和催化剂对聚丙氨酸分子质量的影响,为合成出具有使用要求分子质量的功能高分子材料创造必要条件。丙氨酸的四氢呋喃悬浮液在 0 ℃缓慢通入过量的干燥光气后升温至 30 ℃合成得到了 L-丙氨酸 N-羧基-环内酸酐(L-Ala-NCAs),与传统光气法所用试剂需钠金属回流严格除水所不同的是,本实验仅对所用试剂进行 4 A 分子筛除水处理,简化了实验过程。利用利用红外光谱法确认了所得单体,经过L-Ala-NCAs 精制后得该反应的收率为 61.8 %。研究了 L-Ala-NCAs 的开环聚合反应特性以及反应过程中对聚合物相对分子质量的影响因素。用硝基苯作溶剂,三乙胺作引发剂,单体质量浓度为0.05 g/mL,反应温度为 40 ℃,n(单体)/n(引发剂)=40,反应时间 5 h 时所得聚合物特性黏度最大,特性黏度[η]=0.83 dL/g。考虑到强酸对生物高分子的降解作用,实验中测定了二氯乙酸(DCA)对聚合物特性黏度的影响,结果发现二氯乙酸对聚(L-丙氨酸)特性黏度无影响,说明了二氯乙酸作为聚丙氨酸特性黏度测试溶剂所测得的数据是可靠的。实验结果表明 L-Ala-NCAs 在硝基苯溶剂中开环反应具有逐步聚合反应特征,聚合早期单体很快消失,转变为二聚体、三聚体等低聚物,反应一开始单体的转化率就很高。通过 DSC 法测得聚丙氨酸具有很高的分解温度,分解温度为 396.8 ℃。利用红外光谱法、13C 固体核磁共振法(NMR)对所得到的聚合物进行结构表征,证实了该聚合物确为聚丙氨酸,其化学结构式如下: I<WP=4>OC CH NH nCH3聚丙氨酸主链虽具有聚酰胺的相似结构,但实验中发现其不溶于一般的聚酰胺溶剂,而只能溶于二氯乙酸和三氟乙酸等强的无机酸中。实验结果表明紫外线和微生物对聚丙氨酸均具有降解作用,而聚酰胺在氧化和紫外线作用下会逐渐降解。由于聚丙氨酸主链存在大量的肽键,受微生物和酶的作用,可降解生成为无毒的短肽分子和氨基酸单体。因而聚丙氨酸具有优良的生物可降解性和紫外降解性。更多还原

【Abstract】 Poly(amino acid) is a kind of biodegradable macromolecule materials with lowtoxicity, excellent biocompatibility, biodegradability and bioabsorbability in vivo.They are used very widely, especially are used in pharmaceutical and biomedicalareas such as drug delivery systems and tissue engineering. But the application ofpoly (amino acid) is closely associated with the polymer’s molecule weight, there aremany methods of synthesis poly (amino acid), however the majority of amino acidjust polymerizes through the method of amino N-Carboxyl-α-amino acidAnhydride(NCAs) that can get high molecule weight poly(amino acid). At present thechiefly reports are poly(glutamic acid), poly(aspartic acid) and poly(leucine acid) etc.,and that as the most important part of silk albumen the research of poly(alanine) isvery lack. The paper relates to the preparation of L-Ala-NCAs from L-Alanine andresearches the influence of initiator, reaction temperature, solvent and catalyst on themolecular weight of poly(alanine) in L-ala-NCAs ring-opening polymerization, setthe stage for synthesis functional macromolecule materials with accessible moleculeweight.The excess of gaseous phosgene passed into the suspension of L-Alanine andpurified anhydrous tetrahydrofuran(THF)at 0 ℃ and then heated to 30 ℃, theCarboxyl-L-Alanine acid anhydride (L-ala-NCAs) was synthesized. The solvents inthe experiment just are purified to remove the water by 4? molecular sieve, simplifiedthe procedure of the experiment, it different from conventional gaseous phosgenemethod that the solvents must be rigorously purified to remove all traces of water. Theproduct was confirmed by IR. The L-Ala-NCAs was refined from ligroine and ethylacetate and its yield was 61.8 %.This paper relates to investigate the characteristic of L-ala-NCAs’s ring-openingpolymerization and the influence of various factor on the molecule weight ofpoly (alanine). Nitrobenzene as solvent, triethylamine as initiator, monomerconcentration is 0.05 g/mL, reaction temperature is 40 ℃, n(monomer)/n(initiator) III<WP=6>40 and reaction time is 5 h , the intrinsic viscosity [η] of poly(alanine) thus obtainedexhibits 0.83 dL/g at concentrations 5mg/mL solution. The influence of dichloroaceticon the intrinsic viscosity [η] was also examined. The result showed that thedichloroacetic had no influence on the intrinsic viscosity [η] of poly(alanine) and theresult of polyalanine’s intrinsic viscosity is reliable. The result of experiment alsoshowed that the ring-opening polymerization of L-Ala-NCAs in nitrobenzene solventhad stepwise polymerization characteristic. The monomer disappeared soon in theearly stage and converted to oligomer, the conversion was also very high at the firststage.The decomposing point of poly(alanine) was measured by Differential ScanningCalorimetry(DSC), the result of the decomposing point of poly(alanine) was 396.8 ℃.The poly(alanine) was characterized by Fourier transform infrared spectrometry ( FT-IR), 13C nuclear magnetic resonance spectroscopy(NMR), all results can besummarized to confirm that the sample was poly(alanine) and possessed the followingchemical structure: OC CH NH n CH3The chain of poly(alanine) have the similarity as polyamide, but the poly(alanine)didn’t dissolve in the polyamide’s solvent, it could dissolve in dichloroacetic ortrifluoroacetic acid.The result also showed the UV and microorganism had degradable effect on thepoly(alanine). For peptide bond existing in the poly(alanine) main chain, thepoly(alanine) can be degraded to non-toxic short peptide and amino acid monomerunder the microorganism and enzymes action, so the poly(alanine) are biocompatibleand biodegradable polymers.更多还原