【作者】 易方平；

【导师】 郑思珣；

【作者基本信息】 上海交通大学 ， 材料学， 2009， 博士

【摘要】 本论文运用可逆加成-裂解链转移自由基聚合(RAFT),原子转移自由基聚合(ATRP),开环聚合(ROP)以及点击化学(click chemistry)相结合的方法,设计合成了一系列具有不同组成的AB型两嵌段共聚物以及不同拓扑结构的ABC型三嵌段共聚物,用核磁共振(NMR)和凝胶渗透色谱(GPC)对其进行表征。然后将其分别与不同的热固性聚合物的预聚体共混,固化,最终得到了一系列具有有序/无序纳米结构的热固性树脂,通过原子力显微镜(AFM)、小角X射线散射(SAXS)、差热分析(DSC)、红外光谱(FTIR)、扫描电子显微镜(SEM)、动态力学分析(DMA)等技术对样品的微结构以及热力学性能进行了研究,利用表面元素分析、静态接触角分析等技术对热固性共混体系的表面性能进行了研究。主要研究结果如下:1.经自组装方法形成的纳米尺度上微结构的研究运用RAFT聚合方法,设计合成了一系列不同组成的AB型两嵌段共聚物,聚丙烯酸三氟乙酯-b-聚氧乙烷(PTFEA-b-PEO)、聚甲基丙烯酸缩水甘油酯-b-聚丙烯的酸三氟乙酯(PGMA-b-PTFEA),再将这些嵌段共聚物与环氧树脂共固化。研究发现:嵌段共聚物PTFEA-b-PEO和PGMA-b-PTFEA在环氧树脂中通过自组装机理形成了有序的纳米结构。此外,低表面能的PTFEA链段随着固化反应的进行,会发生表面迁移现象,因此,含氟嵌段共聚物改性后的环氧树脂表面疏水性能得到了很好的改善。通过对含嵌段共聚物PGMA-b-PTFEA的环氧树脂的应力场强度因子的测定,发现改性后材料的韧性得到了很好的改善。2.固化剂类型对纳米结构形成的影响结合RAFT、ROP以及点击化学方法,设计合成了星型杂臂聚氧乙烯-b-聚己内酯-b-聚苯乙烯[star(PEO-b-PCL-b-PS)]。再将其与环氧热固性树脂共混,分别在两种不同的固化剂,3, 3’-二氯-4,4’-二氨基二苯基甲烷(MOCA)和4, 4’-二氨基二苯砜(DDS),固化。通过用原子力显微镜(AFM)和小角X散射(SAXS)研究发现,共混体系中出现了不同的纳米结构,当MOCA作为固化剂时,得到的是球形粒子和层状结构,当而在DDS为固化剂时,体系中呈现出囊泡结构。3.自组装纳米结构存在条件下的反应诱致相分离的研究首先运用两步ATRP聚合方法,成功地制备了两端呈线性,中间呈刷状的ABC三嵌段共聚物,聚己内酯-b-刷型聚二甲基硅氧烷-b-聚苯乙烯(PCL-b-brush-PDMS-b-PS)。接着将该嵌段共聚物与环氧树脂共固化。用AFM和SAXS技术对改性后环氧树脂的形态结构进行研究。研究结果表明,PCL-b-brush-PDMS-b-PS在环氧树酯中形成了囊泡结构。根据嵌段共聚物中各链段与环氧树脂的相容性可知:这种纳米结构的形成机理是在自组装存在条件下的反应诱致相分离机理。4.运用热固性树脂中纳米结构形成方法制备多孔性材料研究首先设计合成了嵌段共聚物聚甲基丙烯酸甲酯-b-聚四乙烯基吡啶(PMMA-b-P4VP),将其与酚醛树脂共混,研究发现嵌段共聚物在共混体系中能通过反应诱致相分离的机理形成纳米结构。将具有纳米结构的酚醛树脂在氮气氛围下高温炭化,可以得到结构均一的具有纳米孔的炭材料。接着根据嵌段共聚物在热固性树脂交联网络中可以形成纳米结构的方法,通过RAFT聚合方法设计合成了带有反应性官能团(环氧基)的嵌段共聚物聚甲基丙烯酸缩水甘油酯-b-聚苯乙烯(PGMA-b-PS),再将该嵌段共聚物与氨丙基三甲氧基硅烷反应,使PGMA链段上的环氧基变为甲氧基硅烷,最后加入正硅酸乙酯,在酸性条件下水解缩合,溶胶-凝胶后,在空气氛围下高温烧结,最终得到了孔径均一,分布均匀的纳米孔二氧化硅材料。当嵌段共聚物PGMA-b-PS含量为40wt%时,二氧化硅材料的比表面积达到了405 m2 /g。5.化学交联聚合物水凝胶中具有纳米尺度疏水微区的形成及其凝胶行为研究通过化学方法,将疏水性的聚苯乙烯(PS)链段均匀地接枝到聚异丙基丙烯酰胺(PNIPAAm)水凝胶的交联网上。由于PNIPAAm链段与PS链段不相容,因此,PS链段在PNIPAAm-g-PS的交联网络会形成纳米微区。通过溶胀,去溶胀和再溶胀试验研究发现:与纯PNIPAAm水凝胶相比,改性后的水凝胶具有快速响应性和较好的机械性能。更多还原

【Abstract】 A series of AB-type diblock copolymers and ABC triblock copolymers were synthesized via combination of reversible addition-fragmentation transfer polymerization (RAFT), atom transfer radical polymerization (ATRP), ring-opening polymerization (ROP) and click chemistry. Nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC) were employed to characterize these block copolymers. These block copolymers were incoporated into thermosetting polymers to access ordered and disordered nanostructures via self-assembly and reaction-induced micrphase separation mechanism. The morphorlogy and thermomechanical properties of the nanostructured thermosets were investigated by means of atomic force microscopy (AFM), scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FTIR). The surface properties were examined by means of surface elemental analysis, static contact angle analysis and energy dispersive X-ray spectroscopy (EDS). The main results are being summarized as below: 1. Formation of nanostructures in epoxy thermosets via self-assembly mechanismSeveral AB-type diblock copolymers such as poly(2,2,2 -trifluoroethyl acrylate)-block-poly(ethylene oxide) (PTFEA-b-PEO), poly(glycidyl methacrylate)-block-poly(2,2,2-trifluoroethyl acrylate) (PGMA-b-PTFEA) were defigned and synthesized through the approach of RAFT polymerization. These block copolymers were incoporated into epoxy resin to access the nanostructures in the thermosets via self-assembly mechanism. The nanostructured thermosets were obtained via non-reactive and/or reactive mixing of the block copolymers with the epoxy matrices. It was found that the formation of the nanostructures in thermosets can optimize the interactions between epoxy matrix and the modifiers and thus the fracture toughness of the materials were significantly improved. In addition, the enhancement in surface hydrophobicity of the thermosets was obtained with the inclusion of the amphiphilc block copolymers. The improved surface properties have been interpretated on the basis of the surface migration of the hydrophobic blocks of the copolymers.2. Effect of curing agent on nanostructured thermosets containing star miktoarm terpolymers poly(ethylene oxide)-block-poly(ε-caprolacton- -e)-block-polystyrene (star (PEO-b-PCL-b-PS)) The star miktoarm terpolymer, star (PEO-b-PCL-b-PS) was firstly synthesized by the combination of RAFT polymerization, ROP and click chemistry. The block copolymers and DGEBA were cured with 4, 4’-methylenebis (2-chloroaniline) (MOCA) or 4, 4’-diaminodiphenylsul- -fone (DDS) as curing agent, respectively. The morphology of the thermosets was examined by means of atomic force microscopy (AFM) and small angle X-ray scattering (SAXS). It is found that different nanostructure appeared in all the samples. Spherical and lamellar structures appeared when MOCA as hadener, while vesicles were obtained when the the curing agent was DDS. The dependence of morphological structures on the types of aromatic amines for epoxy and star (PEO-b-PCL-b-PS) thermosetting blends were interpreted on the basis of the difference in hydrogen bonding interactions resulting from the structure of the curing.3. Study on the reaction-induced microphase separation in the present of self-organized nanostructurePoly(ε-caprolactone)-block-brush-poly(dimethylsiloxane)-block- polystyrene (PCL-b-brush-PDMS-b-PS) terpolymers were synthesized via sequential ATRP, Then the terpolymers was incorporated into epoxy to obtain nanostructure.The morphology of the thermosets was examined by AFM and SAXS.The results of the AFM and SAXS indicated that vesicles were formed in the thremosets.According to the miscibility between terpolymer and thermosets, it was judged that the nanostructure was obtained by the mechanism of the reaction-induced microphase separation in the present of self-organized nanostructure.4. Preparationof nanoporous materials according to the mechanism of reaction-induced microphase separation reported in thermosetsFirstly, Poly (methyl methacrylate)-block-poly (4-vinylpyridine) (PMMA-b-P4VP) block copolymer was synthesized by RAFT polymerization. Secondly, PMMA-b-P4VP was mixed with phenolic resin. It was found that nanostructure was formed via the reaction-induced microphase separation mechanism. The nanostructure thermosets were then carbonized under nitrogen atmosphere, and uniform nanoporous carbon materials were obtained. In addition, nanoporous silica material was prepared too. Firstly, poly (glycidyl methacrylate)-block-polystyrene (PGMA-b-PS) were synthesized through RAFT polymerization. Secondly, the triethoxysilane group was clicked to the PGMA segment by the reaction of PGMA-b-PS block copolymers with 3-aminopropyl-triethoxysilane. Thirdly, the improved block copolymer PGMA-b-PS, TEOS was blended and hydrolyzed under acidic conditions. After condensation, sol-gel and pyrolysised, the nanoporous silica material with uniform distribution were finally prepared. 5. Formation of hydrophobic microphase-separated morphology and study of thermo-responsive properties of PS block-containing PNIPAAm hydrogelsRAFT polymerization was employed to prepare the crosslinked poly (N-isopropylacrylamide)-graft-polystyrene copolymer networks (PNIPAAm-g-PS). Due to the immiscibility of PNIPAAm with PS, the PNIPAAm-g-PS crosslinked copolymers displayed the microphase-separated morphology. While the PNIPAAm-g-PS copolymer networks were subjected to the swelling experiments, it is found that the PS block-containing PNIPAAm hydrogels significantly exhibited faster response to the external temperature changes according to swelling, deswelling, reswelling experiments than the conventional PNIPAAm hydrogels. The improved thermo-responsive properties of hydrogels have been interpreted on the basis of the formation of the specific microphase-separated morphology in the hydrogels, i.e., the PS chains pendent from the crosslinked PNIPAAm networks were selfassembled into the highly hydrophobic nanodomains, which behave as the microporogens and thus promote the contact of PNIPAAm chains and water.更多还原