【作者】 陈博；

【导师】 邓建平；

【作者基本信息】 北京化工大学 ， 化学， 2011， 博士

【摘要】 螺旋聚合物的设计合成,一直以来都是聚合物科学研究领域的热点和重点之一。在已合成的螺旋聚合物中,有关螺旋聚炔的研究最为深入。尽管如此,制备所得具有螺旋结构聚炔普遍具有低溶解性特征,这就在极大程度上限制了其应用,这是我们所不希望看到的。本课题中,我们摒弃传统有机溶剂溶液聚合方法,首次采用催化微乳液聚合法制备取代乙炔类螺旋聚合物乳液,以其为种子乳液,进而制备一系列具有光学活性新型核壳纳米粒子,并研究其手性诱导异构选择结晶性能。主要研究内容如下：采用催化微乳液聚合法在水相体系中制备取代乙炔类螺旋聚合物。制备所得粒子约为70-110纳米左右。粒子由手性取代乙炔螺旋聚合物组成,故能够显示出很强光学活性。聚合在油溶性铑金属催化剂催化条件下,以SDS和曲拉通X-100为乳化剂,DMF为助乳化剂,成功制备得到四种取代乙炔螺旋聚合物,分别为两种手性聚炔丙磺酰胺(po1y1和po1y2)、一种手性聚炔丙脲(po1y3)、一种非手性聚炔丙酰胺(po1y4)。制备所得手性聚合物乳液纳米粒子及除去乳化剂助乳化剂所得螺旋聚合物均具有很强光学活性,聚合物具有规整二级结构,相比较采用传统有机溶剂催化聚合制备所得螺旋聚合物,光学活性和稳定性大大增强。催化微乳液聚合能够使聚合物更倾向于生成单手螺旋构造。在此基础上,选用手性聚合物1(poly 1, PSA)光学活性微乳液,通过在同一体系中引入水相催化微乳液聚合和自由基聚合,制备得到新型核壳纳米粒子乳液。核壳纳米粒子内核由光学活性螺旋取代聚乙炔组成,壳层则由烯类聚合物组成,因此能够表现出很强光学活性。烯类聚合物壳层交联可进一步增强粒子性能。同一体系中引入催化微乳液聚合和自由基聚合思路对于制备新型核壳纳米粒子意义重大,同时也实现了单一种类材料“手性”和“纳米”概念的渗透融合。遵循上述制备思路,通过在同一体系中引入取代乙炔单体SA的催化微乳液聚合和TEOS的sol-gel approach,制备得到新型杂化核壳纳米粒子。粒子内核同样由具有光学活性螺旋取代聚乙炔组成,壳层则由无机硅(silica)构成。Silica壳层使制备所得杂化核壳纳米粒子具有很强光学活性和稳定性,进一步保护内核PSA。有机螺旋聚合物和无机硅两大研究领域在同一体系中首次结合,实现了重大突破。所得杂化核壳纳米粒子可用于对丙氨酸异构体手性诱导异构选择结晶分离,具有广阔应用前景。同一体系中引入制备PBA内核的自由基聚合,制备PSA中间壳层的催化微乳液聚合及制备silica外部壳层的sol-gel approach,通过去除PBA内核,制备得到新型空心有机-无机杂化双层纳米粒子,中间壳层由光学活性PSA组成,外层壳由silica构成。空心双层纳米粒子可以实现大小及壳层厚度可控。手性取代聚乙炔PSA中间层使空心双层纳米粒子具有很强光学活性。空心双层纳米粒子作为手性模板可以实现对丙氨酸异构体手性诱导异构选择结晶分离,且手性分离效率较高,这一结果预示着空心纳米粒子在手性材料技术领域所具有的潜在应用前景。TEM, SEM表征可观测到诱导结晶全过程。同一体系中引入自由基聚合、催化微乳液聚合和sol-gel approach制备空心多层纳米粒子方法具有高度重要性和新颖性。最后,合成螺旋聚乙炔被用于在有机溶剂均相体系中,对BOC-alanine异构体进行诱导异构选择结晶,并取得了较好的手性分离效果。油相体系中所进行的诱导结晶实验,是人工合成螺旋聚合物应用于诱导结晶的直接证据。本课题为螺旋聚合物及基于螺旋聚合物的新型手性材料制备提供了新思路新方法。更多还原

【Abstract】 Design and synthesis of polymers with well-defined structures has always been one of the most active fields in polymer chemistry. Acetylene-based helical polymers are typical synthetic helical polymers. However, these helical polymers unfortunately exhibited low solubilities, thus severely hampering any investigations with regard to their potential applications. In the present research, a series of stable helical polymer enmulsions were obtained by catalytic microemulsion polymerization of substituted acetylene monomers in aqueous systems, following which the novel categories of functional core/shell NPs were successfully prepared and further employed for enantioselective crystallization of amino acid enantiomers on the basis of our earlier investigations.The catalytic microemulsion polymerization supported for the synthesis of substituted polyacetylenes with helical structure in aqueous medium, providing NPs (70-110nm in diameter) consisting of helical polymers and exhibiting large optical activities. Four types of substituted acetylenes:one achiral N-propargylamide (poly4), two chiral N-propargylsulfamides (polyl and 2), and chiral N-propaygylureas (poly3) were polymerized in the presence of hydrophobic Rh-based catalyst and with SDS/Triton X-100 as emulsifier and DMF as co-emulsifier. The NPs and thus-prepared polymers after removing the emulsifier and coemulsifier showed much stronger CD signals, the helices were found to have higher thermal stability when compared with the corresponding polymers synthesized via catalytic polymerizations in organic solvents. Catalytic microemulsion polymerization enable the polymers to form predominantly one-handed helical structures.A new class of core/shell nanoparticles were synthesized by combining aqueous catalytic microemulsion polymerization and free radical polymerization in one specific system by using polyl (PSA) microemulsion as seeded emulsion. The NPs consist of a unique core (composed of an optically active helical-substituted polyacetylene) and a shell (composed of a vinyl polymer) and thus exhibit optical activities. The shells could be further cross-linked for improving the properties of particles. This novel methodology for preparing new class of core/shell NPs are of high importance for combining catalytic polymerization and free radical polymerization in one system and the integration of "chirality" and "nano" concepts in one single material.By following above investigations, a novel category of hybrid NPs consisting of a unique organic core (composed of optically active helical polyacetylene) and an inorganic shell (composed of silica) was synthesized by combining the aqueous catalytic microemulsion polymerization of SA to form the core and the sol-gel approach of TEOS to form the silica shell also in one system. The silica shells enabled the emulsions to exhibit high stability, and the NPs possessed large optical activities, arising from the helical polymer chains constituting the core, two diverse research fields (organic helical polymers and inorganic materials) combining for the first time in a specific system was unprecedented. The obtained novel core/shell NPs induced enantioselective crystallization of alanine enantiomers, attesting to the potential applications of the hybrid core/shell NPs.n-butyl acrylate (BA) underwent free radical polymerization to form PBA cores, followed by the subsequential formation of two shells respectively by catalytic polymerization of SA and sol-gel approach of TEOS, a novel category of hollow organic@inorganic hybrid two-layered NPs, in which the inner layer was formed by optically active PSA while the outer layer by silica were preapred by removing PBA cores. The size and shell thickness of the NPs were tunable. Such NPs showed remarkable optical activity arising from helical substituted polyacetylenes forming the inner layer. The hollow NPs were further successfully used as chiral templates to induce enantioselective crystallization of racemic alanines with considerable e.e. value demonstrating the significant potential applications of the interesting hollow chiral NPs in chiral technologies. The detailed process of the induced crystallization was observed by TEM and SEM. The present strategy for preparing the hollow hybrid chiral NPs is worthy to be highlighted since it combines for the first time free radical polymerization, catalytic polymerization with sol-gel process in a single system.Finally, synthetic helical polyacetylenes were investigated for inducing enantioselective crystallization of BOC-alanine enantiomers from initial homogeneous solutions with considerable e.e. value. This is the first direct evidence of the role of synthetic helical polymers in inducing enantioselective crystallization.The present study opens new possibilities for preparing helical polymers and novel chiral materials based on helical polymers, a large number of advanced functional materials will be accessible.更多还原