【作者】 侯小东；

【导师】 曹阿民；

【作者基本信息】 上海交通大学 ， 高分子化学与物理， 2009， 博士

【摘要】 纳米材料因具有特殊物理、化学性质在催化、超导、复合材料、生物科技等许多领域具有广泛的应用前景,已经成为二十一世纪材料科学研究的前沿。利用分子自组装过程,将无机纳米粒子负载到嵌段共聚物的有序微观分相结构中是制备纳米粒子/嵌段共聚物杂化材料十分有效的一条途径。我们受到大分子能够通过手性相互作用形成有序的自组装聚集体的启发,希望在嵌段共聚物自组装、纳米粒子自组装之外引入手性相互作用的理念,从而通过这三种推动力的协同作用促进纳米粒子在嵌段共聚物母体内的有序化分布,制备出具有实际应用价值的纳米粒子/嵌段共聚物杂化材料。围绕这一目标,本论文主要开展了以下几个方面的工作:一、具有光学活性的嵌段共聚物聚苯乙烯-b-聚乳酸的设计、合成及表征运用原子转移自由基聚合(ATRP)和开环聚合(ROP)设计、合成了两个系列分子量范围在29.5~76.1 KDa、分子量分布窄(PDI=1.11~1.23),且光学纯度高的PS-b-PLA两嵌段聚合物,通过核磁共振(1H NMR)、凝胶渗透色谱(GPC)、热失重分析(TGA)和旋光仪(OR)等多种手段对其化学结构和热性能进行表征分析。依照类似的方法合成了两个系列光学活性的聚乳酸,并同样进行化学结构表征。二、新型含巯基的生物可降解聚乳酸及其修饰CdSe纳米粒子的设计、合成及性能研究设计、合成了一系列结构对称的聚乳酸PLLA-SS-PLLA,进一步还原成α-羟基-ω-巯基聚乳酸HO-PLLA-SH,然后通过与TOPO@CdSe进行配体交换方法合成了核壳结构的量子点HO-PLLA@CdSe QD-I系列。在另外一条途径中,首先通过与TOPO@CdSe进行配体交换反应,合成了11-巯基-1-十一醇(MUD)修饰的量子点MUD@CdSe QD,然后原位聚合合成了另外一种核壳结构的量子点HO-PLLA@CdSe QD-II系列。最后通过1H NMR和傅立叶变换红外光谱(FT-IR)表征上述两种方法合成的量子点化学结构,并通过广角X射线衍射(WAXD)和透射电子显微镜(TEM)和紫外(UV-vis)、荧光光谱(PL)分别表征了其晶体结构和荧光性能,重点考察影响量子点荧光性能的因素。三、基于聚乳酸手性相互作用的立体复合物聚集体的生长动力学及形成机理研究系统研究了PS-b-PLLA和PS-b-PDLA在非选择性溶剂中原位形成立体复合物聚集体的过程,重点讨论样品制备条件对立体复合物生长动力学和最终形态的影响。在此基础上提出本体系的原位自组装机理:光学异构的PLA嵌段之间立体复合作用是自组装聚集体形成的唯一驱动力。最后,以量子点标记的PDLA作为荧光探针,利用共聚焦激光扫描荧光显微镜(CLFM)直观地监测立体复合物聚集体形成过程,从而进一步验证上述自组装机理。四、手性嵌段共聚物PS-b-PDLA的结晶行为研究运用示差扫描量热分析仪(DSC)和温度调制示差扫描量热分析仪(MDSC)研究PS-b-PDLA嵌段共聚物的热性能和等温和非等温结晶动力学结晶行为。结果表明:随着PDLA在嵌段共聚物中组分的减少,热性能和结晶能力都有所降低。当加入少量的PLLA后,形成少量的立体复合物非常有利于PDLA结晶,但是加入量太多时,反而使综合结晶能力有所下降。用偏光显微镜(POM)研究球晶的生长动力学的结果表明:PS-b-PDLA在等温条件下能形成球晶,但是球晶的生长速度与结晶温度、PDLA嵌段的链长以及外加PLLA的量有关系。五、基于手性相互作用的无机纳米粒子/嵌段共聚物纳米复合材料的研究首先,利用小角X射线散射(SAXS)研究了PS-b-PDLA样品在本体中的微观分相,发现微观分相的有序度与样品的状态和测试温度有关系,而且可以通过等温结晶、退火或者流变剪切等方式来提高。其次,在中性表面上研究了PS-b-PDLA嵌段共聚物薄层在不同因素影响下的自组装行为。最后重点考察了纳米粒子的加入对嵌段共聚物本体和薄层微观分相的影响。总之,利用聚乳酸链段的分子间相互作用力,通过嵌段共聚物PS-b-PDLA的微观相分离并借助等温结晶、溶剂退火等方法,可以获得有序的纳米粒子/嵌段共聚物纳米杂化材料,从而为简单地制备具有工业应用价值的、有序的嵌段共聚物纳米模板提供一条新的思路。更多还原

【Abstract】 Nano-materials have been extensively applied in catalyst, superconductor, composite material and biotechnology et al, due to their specific physical and chemical properties, which is becoming the hot-point in the field of material science in 21th century. Loading organic nanoparticle into microphase-separated block copolymer matrix by molecular self-assembly is an effective approach to prepare high-ordered nanoparticle/block copolymer hybrid. Inspirited by the fact that macromolecules can self-assembly into ordered aggregate by recognition, we hope to prepare high ordered nanoparticel/block copolymer hybrid by combining the self-assembly of block copolymer and nanoparticle with chiral recognition. In order to reach this goal, research works in this thesis was divided into several parts as following:1. Design, synthesis and characterization of optical active block copolymer PS-b-PLLA and PS-b-PDLA and their homopolymer PLLA and PDLAFirst, a series of enantiomeric PS-b-PLLA and PS-b-PDLA diblock coplymer bearing a PS (Mn,NMR=30.0 KDa, PDI=1.11) and various PLA blocks were synthesized via combination of ATRP of styrene and living ring-opening polymerization (ROP) of enantiomeric l-/d-lactide. By means of nuclear magnetic resonance spectrometer (NMR), gel permeation chromatography (GPC), polarimeter and thermal gravimetrical analyzer (TGA), macromolecular structures and therm physical properties of the synthesized diblock copolymers were characterized. By the same approach, two series of homopolymer PLLA and PDLA were also synthesized and characterized.2. Design and syntheses of new biodegradable poly(l-lactide) disulfides and successive preparation of their stabilized photoluminescent CdSe Quantum Dots HO-PLLA@CdSe QDFirst, new aliphatic poly(l-lactide) disulfides HO-PLLA-SS-PLLA-OH were designed and synthesized and then were reduced intoα-hydroxyl-ω-mercapto heterofunctional poly(l-lactide) (HO-PLLA–SH).With these less toxic HO-PLLA–SH , photoluminescent CdSe QDs (HO-PLLA@CdSe QD-I series) were successively prepared through a surface ligand exchanging process. In an alterative strategy, the biodegradable poly(l-lactide) surface stabilized CdSe QDs (HO-PLLA@CdSe QD-II series) were comparatively synthesized by surface hydroxyl initiated ROP of (l-)-lactide from a prepared 11-mercapto-1-undecanol (MUD) stabilized CdSe QD precursor (MUD@CdSe QD).Chemical and crystal structures of the two series of QDs were characterized by NMR ,FT-IR ,WAXD,TEM ,UV and PL,the effect of preparation conditions on the quantum yields (QY) were investigated in detail.3. Growth kinetic and mechanism of stereocomplex aggregates by PS-b-PLLA/PS-b-PDLA (or PLLA) in nonselective solventIn-situ self-assembly in non-selective solvents THF was explored at ambient temperature for the mixtures of a pair of enantiomeric diblock PS-b-PLLA and PS-b-PDLA. It was noted that the growth kinetic of in-situ self-assembly depended on the concentration and molecular weight of enantiomeric PLA block population as well as preparation condition such as agitation, and the isolated self-assemblies were found to form PLLA/PDLA racemic crystal structures as analyzed by means of DSC, WAXD, and FT-IR. Therefore, in a view of the mechanism of aggregations formed in current system, it was suggested to be solely driven by the interplay of stereocomplexation between the PLLA and PDLA blocks. At last, utilizing the new achieved HO-PDLA@CdSe QD as a suitable fluorescent label, in-situ aggregation in THF driven only by the stereocomplexation of enantiomeric PLLA and PDLA blocks and morphologies of the aggregated stereocomplex microparticles were investigated by confocal laser fluorescent microscope (CLFM) and SEM.4. Thermal physical properties and crystallization behavior of chiral block copolymer PS-b-PDLAWith the help of DSC and MDSC, the thermal physical properties and crystallization of PS-b-PDLA were investigated and compared with homopolymer PDLA. It was found that: with the decrease of PDLA block length, therm physical parameters and crystallization capability of PS-b-PDLA reduce accordingly,and adding PLLA can improved the thermal property and crystallization capability of PS-b-PDLA due to the nucleation of stereocomplex. However, too much addition of PLLA resulted in retain of PDLA in the abundant stereocomplex matrix, which would reduce the total crystallization capability of PS-b-PDLA. The study on the growth kinetic of spherocrystal by POM displayed that growth rate of spherulite of PS-b-PDLA depended on the isotherm temperature, volume fraction of PDLA block and amount of PLLA.5. Study on the organic nanoparticle/block copolymer hybrid based on the chiral recognition and self-asssembly of block copolymer and nanoparticleAt first, the study on the micro-phase behavior of PS-b-PDLA in bulk by SAXS showed that the degree of order of micro-phase separated domain not only depended on the state of sample and temperature, but can be improved by means of method such as isotherm crystallization, annealing and shearing et al.Then, dependence of preparation conditions on the self-assemble behavior of PS-b-PDLA thin film on a neutral surface was investigated in detail. At last, the effects of incorporation of nanopartilcles on the microphase speration behavior of block copolymer in bulk and in thin film were investigeated in detail.In summary, high ordered nano-particel/block copolymer hybrid can be obtain by combining the self-assembly of block copolymer and nanoparticle with chiral recognizing, and the degree of order of micro-domain can be improved by isotherm crystallization and solvent annealing et al. Therefore, current result provided an alternative facile way to prepared industrial applicable and high-ordered nanoparticle/block copolymer template.更多还原