【作者】 曾科；

【导师】 郑思珣；

【作者基本信息】 上海交通大学 ， 材料学， 2008， 博士

【摘要】 有机-无机复合材料结合了有机材料和无机材料各自的优点,具有显著的优异性能,成为研究的热点。近年来,笼状倍半硅氧烷(POSS)这种有着规整立体结构同时具有单纳米尺度的有机-无机杂化分子更是吸引了各国研究人员的目光。POSS的化学结构式为(RSiO3/2)n,n=6~12,R为有机基团,其中一个或多个为反应性官能团。POSS功能化后带有的不同的有机基团决定了POSS在聚合物中不同的杂化方式。例如,单反应性官能团的POSS通过共聚或者反应性共混接枝到聚合物主链上;而两官能团的POSS可以嵌入到高分子主链中;具有三个以上反应性官能团的POSS可以用作交联剂引入体型的聚合物中。POSS的引入往往使聚合物的一种或多种性能得到改善,如热力学性能,结晶性能,而这种性能上的改善取决于POSS在聚合物基体中的聚集形态。氟丙基取代的POSS是近年来才发展起来的一类全新的多面倍半硅氧烷。由于兼具了有机硅材料以及有机氟材料两者性能上的优势,将其引入高分子材料,将对材料的本体性能乃至表面性能特别是疏水性能产生巨大的影响。但是由于有机硅材料或者含氟材料在溶度参数上与一般的高分子材料存在较大的差异,直接通过物理共混的方式往往导致宏观相分离的发生,很难得到具有理想相结构的复合材料,而具有微观尺度相分离结构的形成是复合材料获得优异综合性能的关键。因此我们有必要对含氟POSS进行分子设计,将其设计成具有可反应性官能团,或者将其引入到具有两亲性质的嵌段当中,以提高POSS与聚合物基体的相容性。在本论文工作中,我们首先成功合成了一系列功能化含氟POSS单体或者含POSS的两亲性嵌段聚合物。然后将其引入到热固性或热塑性的聚合物中,含氟的POSS笼体通过自组装的机理在聚合物基体内形成具有微观尺度的相分离结构,我们利用原子力显微镜、透射电镜以及场发射的扫描电镜直接观察了这一形貌的形成。由于含氟材料本身具有极低的表面能,将其引入到高分子会显著改善材料的疏水性能。我们利用表面接触角测定仪测试了不同液体在材料表面的接触角并由此计算出材料的表面自由能,研究含氟POSS的引入对材料表面性能的影响。本论文工作主要从以下几个方面对含氟POSS在聚合物基体中的自组装行为进行了研究。1.含氟POSS及其两亲聚合物在环氧树脂中的自组装行为研究环氧树脂是一类常用的热固性树脂,性能良好,用途广泛。POSS改性环氧树脂已经有很多文献报道,但是基于含氟POSS的改性还未见报道。源于含氟POSS与环氧树脂在固化前后的不相容性,将其引入环氧树脂,易出现相分离,若将含氟POSS引入到一种具有两亲性质的嵌段共聚物中,借助与环氧树脂相容的其他链段的增容作用,可以将POSS的相分离限制在微观尺度,即含POSS的嵌段共聚物在环氧树脂基体内发生自组装,环氧树脂经固化反应后,这种由自组装形成的微观相结构被固定下来,可以通过可以通过原子力显微镜(AFM)、透射电镜(TEM)以及扫描电镜(SEM)观察这种微相分离的结构,并借此研究含POSS嵌段共聚物的环氧树脂结构与性能间的关系。含氟材料的表面性能一直以来受到研究人员的关注。将含氟POSS引入环氧树脂后,必然对环氧树脂的表面形貌以及疏水性能产生巨大的影响。本论文工作利用原子力显微镜、表面接触角测定仪以及X射线光电子能谱等手段研究了含氟POSS改性环氧树脂的表面性能,并对此作出了解释。我们设计并合成了具有单反应官能团的含氟POSS(氨基POSS),含POSS的两亲性嵌段聚合物(POSS单封端的聚氧乙烯、POSS单封端的聚己内酯以及POSS-聚酚氧-POSS)。这些嵌段聚合物的拓扑结构以及链段性质均有所不同,本文就它们与环氧树脂共混后的相行为以及性能进行了研究。2.含氟POSS改性的功能性聚合物聚异丙基丙烯酰胺(PNIPAM)是一种具有温敏特性的高分子,其水溶液呈现出低临界互溶(LCST)行为。PNIPAM经交联后形成的体型聚合物在水中有明显的体积相转变行为,这些独特的性能使聚异丙基丙烯酰胺在生物医药领域有着很广阔的应用前景。我们设计并合成了单丙烯酸酯基功能化的含氟POSS,通过自由基共聚的方式引入聚异丙基丙烯酰胺的交联体系中,并研究了该杂化凝胶的性能,发现经含氟POSS改性的杂化凝胶相对于纯的PNIPAM水凝胶具有更快的相应速度以及更好的机械强度。聚乙烯亚胺(PEI)是一种水溶性高分子,被广泛应用于生物医药领域。对其进行疏水改性能够降低生理毒性、扩展应用范围。PEI主链上有着数目众多的脂肪族氨基,很容易与环氧基团发生反应,基于这个思路我们设计并合成了带有一个环氧基团的含氟POSS,通过氨基与环氧基团间的反应把含氟POSS引入到PEI的分子链中,从而达到对PEI疏水改性的目的。3.含POSS的遥爪聚合物的形成及其本体性能的研究利用点击化学的方法,合成了具有POSS-PEG-POSS结构的遥爪聚合物。研究了POSS的引入对PEG链段结晶行为的影响。发现在PEG的两端引入POSS使PEG链段的结晶能力下降,这不同于我们之前所研究的POSS-capped PEO两嵌段共聚物。其原因主要是由于分子链的特殊拓扑结构造成的,连接与PEG链段两端的POSS笼体易于聚集而形成物理交联点,从而限制了PEG链段的结晶行为,这种限制作用随PEG分子量的减小,即POSS相对含量的增加而增强。也正是由于POSS聚集所形成的物理交联点的作用,而使得整个聚合物的溶解性能发生了巨大的变化,在共溶剂(如四氢呋喃)中聚合物能很好的溶解,而在选择性溶剂(如水)中,该遥爪聚合物只能被溶胀而不能溶解,即形成了物理凝胶。以含氟POSS作为封端分子,结合超分子组装以及点击化学的方法成功合成了基于PEG/α-环糊精的聚轮烷,运用XRD分析了POSS的引入对超分子结晶性能的影响,发现POSS的引入虽然没有改变超分子的晶体构型,但是影响了其结晶能力,随着超分子中PEG链段分子量的减小,即随着POSS质量分数的增大,超分子的结晶能力逐渐下降。热重分析(TGA)表明,POSS的引入有利于超分子高温热稳定性的提高。以POSS-PEO-POSS作为改性分子,利用溶剂的扩散作用,成功制备了POSS-PEO-POSS改性的聚异丙基丙烯酰胺(PNIPAM)水凝胶。采用物理共混的方法,将疏水链段(POSS)以及亲水链段(PEO)同时引入PNIPAM交联网络中,并研究了改性凝胶的温度响应性能。溶胀、去溶胀以及再溶胀试验表明,POSS-PEO-POSS的引入明显加快了凝胶的温度响应速度,我们从机理上解释了这一结果。结合可逆加成-断裂转移(RAFT)聚合和点击化学的方法,合成了具有POSS-PNIPAM-POSS结构的遥爪聚合物。由于POSS与PNIPAM链段不具有相容性,POSS会在聚合物基体内发生自组装,我们利用原子力显微镜观察了POSS的组装形态。PNIPAM链段在水溶液中有LCST性质,我们以水为溶剂,将该嵌段聚合物配成稀溶液,观察到胶束的形成,利用光子相关光谱(PCS)研究了胶束粒径随温度的变化的变化。更多还原

【Abstract】 The concept of incorporating inorganic (or organometallic) blocks into organic polymers has been widely accepted to obtain the materials with some new and improved properties. Typical POSS molecules possess the nanosized cage-like structures, derived from hydrolysis and condensation of trifunctional organiosilanes with a formula of (RSiO3/2)n,n=6~12,where R can be various types of organic groups, different approaches can be adopted to incorporate POSS molecules into polymers. For instance, the mono-functional POSS monomers can be grafted onto macromolecular chains by co-polymerization or reactive blending whereas the bi-functional POSS monomers will allow ones to incorporate the silsesquioxane building blocks into macromolecular backbones. The multi-functional POSS monomers can be used as curing agents to prepare POSS-containing thermosetting nanocomposites.Fluorinated polyhedral oligomeric silsesquioxanes (FluoroPOSS) are the newest class of POSS compounds. Because they combine both advantages of the fluoro-materials and the organosilicone, it will greatly influence the properties especially the surface hydrophobicity of the target materials when the fluoroPOSS was introduced into them. But because the great difference in chemical structure and composition between the fluoroPOSS and the usual polymer materials, it is difficult to obtain the idea composite by simply physical blending them together. In composites system, getting micro-scaled phase separation act as the key role to obtain a material with outstanding performance. In order to improve the miscibility between the fluoroPOSS and polymer matrix, methods must be done to introduce one or more reactable group into fluoroPOSS molecule, or someamphiphilic copolymers containing fluoroPOSS can be synthesized. All these can make the miscibility between the fluoroPOSS and polymer matrix much better.In this thesis, we successfully synthesis varied functionalized fluoroPOSS monomer or amphiphilic copolymers containing fluoroPOSS. Then these monomers or copolymers were addressed into some thermosets or thermoplastic polymers. With self-assembling mechanism, the phase separation in micro-scale will occur in the polymers’matrix. Atomic force microscopy (AFM), transmission electric microscopy (TEM) and field emission scan electric microscopy (FESEM) were employed to observe the morphologyformed. Due to the low surface energy of the fluorinated materials, the introduction of the fluoroPOSS will greatly improved the hydrophobicity of the polymers’surface. The contact angles on the materials’surface were measured and were further used to calculate the surface energy. The following systems were studied in this thesis.1. the self-assembling behavior of the fluoroPOSS monomers or copolymers in epoxy resinEpoxy resin is a class of thermosets and is widely used for its excellent performance. There have been many report on POSS modified epoxy resin but few on the fluoroPOSS. Because of the difference in the chemical structure between the fluoroPOSS and epoxy resin, macro scale phase separation must be happened when we mix them together. Chemical modification is needed to improve the miscibility between them. Some well defined functionalized fluoroPOSS or amphiphilic copolymers containing fluoroPOSS,for instance, amino-functionalized fluoroPOSS, fluoroPOSS-capped PEO, fluoroPOSS-capped PCL and fluoroPOSS-phenoxy-fluorPOSS, were designed and successfully synthesized.. And these macromonomer or copolymers were further incorporated into the epoxy resin. Due to the amphiphilic characterization of the copolymers, self-assembling would be occurred in epoxy matrix. Adjusting the composition of the copolymers, nanosized phase separation behavior would be obtained. The morphology can be easily fixed via curing reaction and observed by AFM, TEM and SEM. The thermal and mechanical properties can be evaluated by DSC, TGA and DMA.The surface properties of the fluorinated materials are always the interesting area because of their great applied value. After fluoroPOSS introduction, the surface morphology and the hydrophobicity would be greatly influenced. AFM, XPS and contact angle measurement were addressed to value the surface properties of the epoxy resin.2. Functional polymers modified by fluoroPOSSHepta(3,3,3-trifluoropropyl)propylacrylate polyhedral oligomeric silsesquioxane (POSS) was synthesized and used as a monomer of copolymerization to prepare the organic-inorganic poly(N-isopropylacrylamide) (PNIPAM) nanocomposites with POSS content up to 12.5 wt%. The POSS-containing PNIPAM networks can be prepared with N,N’-Methylenebisacrylamide (BIS) as the crosslinking agent. When the organic-inorganic nanocomposites were swollen in water they exhibited the characteristics of hydrogels. With the moderate contents of POSS, the POSS-containing hybrid hydrogels displayed much faster response rates in swelling, deswelling and re-swelling experimentsthan control PNIPAM hydrogel than the PNIPAM hydrogels prepared via the free radical copolymerization of N-isopropylacrylamide (NIPAM) and N,N’-methylenebisacrylamide (viz. the conventional crosslinker). The improved hydrogel properties have been interpreted on the basis of the formation of the nanosized hydrophobic microdomains around the POSS moieties.Polyethyleneimine (PEI) is kind of water-soluble polymer. It is widely used in biomedicine fields for its biocompatibility. Several methods have been employed to improve its hydrophobicity to decrease the physiological toxicity and expend its appliance. There are many amino groups on the PEI chains, and they can react with epoxy group in mild condition. Based on this, fluoroPOSS-capped propyl glycidyl was synthesized. The POSS macromonomer was further applied to modify the PEI. The POSS-PEI compositesshowed the enhanced thermal properties that were proved by the differential scanningcalorimetry (DSC) and thermogravimetric analysis (TGA). The static contact angle measurements indicate that the organic-inorganic nanocomposites displayed a significant enhancement in surface hydrophobicity.3. Synthesis of the telechelic polymer containing fluoroPOSS and its propertiesUsing click chemistry, we designed and synthesis the POSS-PEG-POSS telechelic polymer. Its crystallization behavior was studied by means of DSC and XRD. The results showed that the POSS cages could greatly influence the crystal ability of the PEG chains. With the decrease of the PEG chain’s length, the crystal ability decreased significantly. It’s the result of the special topology of the telechelic polymer. The POSS rich domain can act as physical crosslink points to limit the crystal behavior the PEG chains. The special topology also influence the solubility of the polymer, in selective solvent such as water, POSS-PEG-POSS can only be swelled but can not be dissolve. Physical gel formed due to the strong interaction between POSS cages.A novel polyrotaxane based on polyhedral oligomeric silsesquioxane (POSS),α-cyclodextrin (α-CD) and poly (ethylene glycol) (PEG) was synthesized in this research work. Pesudorotaxanes were prepared based on alkyne terminated PEG andα-cyclodextrin (α-CD) with different PEG chains length. To prevent the dethreading of theα-CD from the PEG chains, azido-POSS was used as block agent to close the both ends of the pesudorotaxanes via“Click Chemistry”, and convert the pesudorotaxanes to the polyrotaxane. X-ray diffraction (XRD) results showed that the channel-type inclusion complexs were formed for all the polyrotaxane, but their crystal structure were slightly different with the corresponding pesudorotaxanes. And the crstalization ability of the polyrotaxanes were decreased with the decreasing of the PEG chains’length, which means that the introduction of the POSS can inflence the crystal behavior of the supramolecules due to its bulky effect. Thermal stability of the polyrotaxane was improved comparing to the pesudorotaxane by introducing the POSS.The amphiphilic tri-block copolymer POSS-PEG-POSS was used as the modifier to improve the temperature response rate of poly(N-isopropylacrylamide) (PNIPAM) hydrogels. The modified PNIPAM hydrogels exhibited temperature-responsive behavior as to the control organic hydrogels. It is identified that all the modified PNIPAM hydrogels displayed much faster response rates in terms of swelling, deswelling and re-swelling experiments than the control PNIPAM hydrogel. The improved hydrogel properties could be interpreted on the basis of the synergetic effect between the hydrophobic parts (POSS) and hydrophilic parts (PEG). Hydrophobic POSS cage will self-assemble due to its immiscibility with other components. Hydrophobic micro-domains can be formed and increase the contact area between the water and PNPAM network. Therefore the response rate can be improved. At the same time, the hydrophilic PEG component can act as channel for water in/out and facilitate the diffusion of water in PNIPAM network. From this aspect, the response rate of hydrogels can also be improved.Combine the reversible addition fragmentation chain transfer (RAFT) and Click chemistry. POSS-PNIPAM-POSS telechelic polymer was synthesized. POSS and PNIPAM are immiscible, the phase separation behavior was observed by AFM. Based on the temperature sensitive properties of the PNIPAM chains, photon correlation spectroscopy (PCS) was employed to study the micelle behavior of the telechelics in dilute solution.更多还原