【作者】 宋文会；

【导师】 王新灵；

【作者基本信息】 上海交通大学 ， 材料科学与工程， 2008， 博士

【摘要】 聚氨酯是由聚酯或聚醚多元醇与氨基甲酸酯重复单元形成的嵌段共聚物。作为一类重要的多用途聚合物材料，它不仅拥有优良的耐磨性能、耐疲劳性、耐化学腐蚀性及高抗冲性、优异的柔顺性和极好的阻尼性，并且具有很好的生物相容性。这些优异的性能使它不断受到重视，并且日益广泛的得到应用。但传统的聚氨酯由于耐热性不足等缺点限制了它在更广阔领域的应用。碳纳米管作为21世纪的新型材料，具有奇异的结构和独特的物理性能，被认为是制备高性能聚合物复合材料最理想的候选填料之一。本文利用碳纳米管优越的热学性能来改善聚氨酯的耐热性，制备聚氨酯/碳纳米管复合材料。随着石油危机日趋加剧以及以石油为原料的高分子对环境造成的影响日益严重，以可再生资源为原料制备环境友好的聚合物越来越成为关注的焦点。聚乳酸来源于可再生的玉米和甜菜等，在环境中可降解为二氧化碳和水，具有优良的生物相容性和生物降解能力。因此本论文以端羟基的聚乳酸为软段来制备环境友好的聚氨酯。碳纳米管在聚合物添加材料应用中的关键问题是解决碳纳米管的分散问题，为了得到一致的分散，提高碳纳米管与聚合物基体的相容性，提高填料和基体之间的相互作用力，本文用原位缩聚的方法将聚乳酸共价键接枝在碳纳米管的表面，并制备端羟基的聚乳酸/碳纳米管预聚物，用脂肪族的二异氰酸酯进行扩链来制备环境友好、性能优越的聚氨酯/碳纳米管复合材料。为了对比不同结构的碳纳米管的接枝情况，本文在相同的条件下对不同结构的碳纳米管进行接枝，研究其接枝前后结构和形貌的变化等。具体研究内容如下：1.不同结构碳纳米管的功能化在相同的条件下，用“grafted to”的方法，将分子量为1000的聚丙二醇分子分别接枝在单壁、双壁、直径为10-20nm和20-30nm的碳纳米管的表面，研究不同结构的碳纳米管在接枝前后结构和形貌的变化。结果表明通过“grafted to”方法成功将聚丙二醇分子接枝在单壁、双壁、直径为10-20nm的多壁碳纳米管和直径为20-30nm的多壁碳纳米管的表面。Raman光谱和透射电镜的分析表明单壁和双壁的碳纳米管由于表面结构比较完善，其表面接枝的聚合物分布不均匀，且厚度均不到1nm，而多壁碳纳米管由于表面缺陷比较多，从而能够更加充分的被羧基化，使其表面比较均匀的接枝上了聚合物，其厚度在5nm左右。通过热失重表征和计算可得，单位质量的单壁碳纳米管上接枝的聚合物质量最高，而直径为20-30nm的多壁碳纳米管，其单位质量上接枝的聚合物质量最低；而对于单位面积碳纳米管上接枝的的聚合物摩尔数来说，直径为20-30nm的多壁碳纳米管的最高，而单壁碳纳米管的最低。2.乳酸原位缩聚功能化碳纳米管以羧基化的碳纳米管、乳酸为原料，在催化剂的作用下，通过原位缩聚的方法，一步法将聚乳酸接枝到碳纳米管的表面。通过红外光谱和热失重分析，接枝聚乳酸的分子量随着缩聚反应时间的增加而增加。当缩聚反应时间由5小时增加到23小时后到达平衡，接枝的聚合物的分子量从400增加到2500左右。通过紫外可见光谱分析可知，制备的聚乳酸功能化的碳纳米管之间没有形成团聚，可以在溶剂氯仿中形成均匀的分散。透射电镜的分析结果表明，不同的缩聚反应时间下制备的样品，碳纳米管的管壁和端口都均匀的包覆了聚合物，而且所包覆的聚合物的厚度随着缩聚反应时间的增加而增加。3.端羟基的聚乳酸/碳纳米管复合物制备及研究分别以初始碳纳米管和羧基化的碳纳米管及乳酸、1，4丁二醇为原料，用原位缩聚的方法制备了不同结构和性能的端羟基聚乳酸/碳纳米管复合物。作为平行实验，同时制备了不加碳纳米管的纯端羟基聚乳酸。TGA的分析表明，与纯的聚乳酸相比，碳纳米管的加入显著提高了端羟基聚乳酸的初始分解温度，其中以加入羧基化碳纳米管的聚乳酸初始分解温度最高。DSC的分析表明以Sn(Oct)2和浓硫酸为催化剂可以分别制备无定形的与结晶的聚乳酸/碳纳米管复合物。碳纳米管的加入使结晶变得容易，起了成核剂的作用，但POM的表征结果表明碳纳米管并没有改变聚乳酸的结晶形貌。FESEM和HRTEM的图片分析说明共价键功能化的碳纳米管能均匀的分散在聚乳酸基体中，这对进一步研究聚乳酸/碳纳米管复合物的性能和应用至关重要，也为进一步研究以聚乳酸为嵌段的环境友好的碳纳米管纳米复合材料提供了理论和技术基础。4．聚氨酯/碳纳米管复合材料制备及研究以端羟基聚乳酸功能化的碳纳米管为交联剂，原位交联制备了聚氨酯/碳纳米管复合材料。与纯的聚氨酯和初始碳纳米管与聚氨酯形成的共混复合物相比，因为碳纳米管的加入和在基体中的均匀分散，使其具有更高的热稳定性。基于聚乳酸制备的聚氨酯嵌段共聚物，由于聚乳酸的绿色特性，不仅使制得的聚氨酯环境友好，更好的生物相容等，还有望使聚氨酯应用在更宽广的领域，尤其是生物医药领域等。更多还原

【Abstract】 Polyurethane is a kind of block copolymer consisting of polyester or polyether softsegments and urethane hard segments. As an important and versatile class of polymermaterial, polyurethane has been receiving increasing attention and has various end usepurposes in a broading area due to its high abrasion resistance, wearability, chemicalresistance, high impact strength, excellent flexibility and outstanding damping ability.However, conventional polyurethane has exhibited poor thermal stability, which limited itsvarious applications. Carbon nanotube(CNT), as a novel material in twenty-first century,was considered to be the most promising candidate as ideal filler owing to its uniquestructure and particular physical properties. In this paper, carbon nanotube was used tomodify polyurethane due to its high thermal stability and to prepare thepolyurethane/carbon nanotube composite.Due to intensifying crisis of oil and enviormental influence of petroleum-basedpolymer, the study on the enviormental benign polymer has been paid increasing attention.Poly(lactic acid) comes from renewable corn or sugar beet etc. and could convent intocarbon dioxide and water after degradation; what’s more, it had good biocompatible andbiodegradable properties. In this paper, poly(lactic acid) was used as soft segment toprepare the enviormental benign polyurethane.Dispersion is the key problem about the application of carbon nanotube in polymercomposite. In order to obtain the homogeneous dispersion of carbon nanotube in thepolyurethane matrix and to increase the compatibility with the matrix and force ofinteraction, carbon nanotube was functionalized with poly(lactic acid) based on in situ polycondensation of lactic acid and carbon nanotube. To prepare for the polyurethane,prepolymer composite was also prepared. Finally the enviormental benignpolyurethane/carbon nanotube was prepared based on the chain extention reaction ofaliphatic diisocyanate and the hydroxyl termintated poly(lactic acid)/carbon nanotubeprepolymer and in situ cross linking of the functionalized carbon nanotube.In order to investigate the functionalization of different kinds carbon nanotubes, thegrafting of different kinds of carbon nanotubes were given under same condition. Thedetails about the studies were shown as following:1. The functionalization of different kinds carbon nanotubesIn order to investigate the variation before and after functionalization of carbonnanotubes, polypropylene glycol of molecular weight of 1000 was grafted on thesingle-walled carbon nanotube, double-walled carbon nanotube and different diametermulti-walled carbon nanotubes.The result showed that polypropylene glycol with molecular weight of 1000 wassuccessfully grafted on the single-walled carbon nanotube, double-walled carbon nanotubeand different diameter multi-walled carbon nanotubes. Raman spectra and TEM analysisdemonstrated that grafted polymer on single-walled carbon nanotube and double-walledcarbon nanotube was not uniform and the thickness was less than 1nm due to the moreperfect structure. Meanwhile different diameter multi-walled carbon nanotubes wereuniform coated with 5nm thickness polymer due to the less perfect structure. The TGAanalysis and calculation of grafting samples indicated that per unit area of single-walledcarbon nanotube achieved the highest quantity of grafting polymer while the per unit massof multiwalled carbon nanotube contain the highest quantity of grafting polymer comparedwith the other kinds of carbon nanotubes.2. The functionalization of carbon nanotube with poly(lactic acid) based on in situpolycondensationThe carbon nanotube was functionalized with poly(lactic acid) based on in situ polycondensantion of carboxlyic carbon nanotube and lactic acid in one step.FTIR and TGA analysis indicated that the molecular weight of grafting polymerswere increased from ca. 400 to 2500 as polycondensation time increased from 5 hours to23 hours equilibrium. UV-Vis spectra showed that the prepared poly(lactic acid)functionalized carbon nanotube dispersed uniform in the solution chloroform without anyaggregation.HRTEM images showed that the grafting polymer were coated uniform on thecircumference and ended parts of carbon nanotubes; what’s more, the thickness of thegrafting polymer increased with the polycondensation time.3. The preparation and study of hydroxyl terminated poly(lactic acid)/carbonnanotube compositeThe hydroxyl terminated poly(lactic acid) prepolymers incorporating pristine CNTsand CNT-COOH respectively were prepared based on in situ polycondensation of lacticacid and 1,4-butanediol. As parallel samples, the pure PLA diol prepolymers weresynthesized at the absence of CNTs. TGA analysis indicated that the initial decompositiontemperature of the prepolymer incorporating CNT-COOH was a little higher than thatincorperating with the pristine and both of them were pronounced higher than pureprepolymer. DSC measurements proved that the amorphous and crystalline prepolymerswere obtained catalyzed by stannous octoate and sulfric acid respectively. The addition ofCNTs made it easy for the polymer to crystallize, however it didn’t change the spheruliticcrystalline morphology from the POM images. FESEM images showed that covalentlyfunctionalization of CNT-COOH contributed the homogeneous dispersion in the polymermatrix, which was essential for the further application. The work was suggested to pavethe way toward carbon nanotube-improved-PLA-based environmental benign blockcopolymer nanocomposites for various end-use purposes.4．The preparation and study of polyurethane/carbon nanotube composite base onin situ cross linking The hydroxyl terminated poly(lactic acid)-functionalized-CNTs were used ascross-linker to form the polyurethane/CNTs composite. Compared with the purepolyurethane and pristine CNTs blend polyurethane composite, such polyurethane/CNTscomposite based on in situ cross-linking of CNTs achieved better thermal properties due tothe uniform dispersion of CNTs. Due to the“green”feature of poly (lactic acid), theas-prepared improved PU composite was environmental benign and may have a broaderpotential application, especial in biology and medicine.更多还原