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含苯基多面齐聚倍半硅氧烷的高分子的结构与性能研究

Phenyl Polyhedral Oligomeric Silsesquioxane (POSS)-containing Polymers: Structure and Properties

【作者】 倪勇

【导师】 郑思珣;

【作者基本信息】 上海交通大学 , 材料学, 2007, 博士

【摘要】 近年来,有机/无机纳米复合材料由于具有独特的性能,因此受到了人们广泛的关注。有机/无机纳米复合材料可以将有机高分子的优点与无机材料的优点结合在一起。多面齐聚倍半硅氧烷(Polyhedral oligomeric silsesquioxane , POSS)作为制备有机/无机纳米复合材料的一种新型有效的原材料得到人们的重视。典型的多面齐聚倍半硅氧烷单体具有笼形结构,其化学通式为:(RSiO1.5)n( n= 6~12, R为有机基团),在其笼形结构的端角上有八个有机基团,其中一个或多个为反应性或可聚合的官能团。多面齐聚倍半硅氧烷具有纳米尺度的分子大小、规整的立方体结构、可反应性或可聚合的官能团、活性基团数量可控以及良好的有机物相容性等特点。各种具有可反应性或可聚合性的POSS分子已被合成出来,并通过与有机单体共聚,在有机/无机组分之间形成稳定的共价键的方式来制备有机/无机纳米复合材料。含POSS的聚合物的多种性能得到改善,如力学性能提高,热稳定性能提高、阻燃性能提高、表面疏水性能提高,熔融结晶行为改变等。1.一种新型可光交联的多面齐聚倍半硅氧烷的合成及其与聚乙烯醇肉桂酸酯纳米复合材料的制备通过肉桂酰氯与八氨基苯基倍半硅氧烷的反应合成了一种新型的具有光敏性的八肉桂酰胺苯基多面齐聚倍半硅氧烷(OcapPOSS)。OcapPOSS与光敏聚合物聚乙烯醇肉桂酸酯(PVCIN)具有很好的相容性,这促使我们运用光固化方式制备PVCIN-OcapPOSS纳米复合材料。测试结果表明PVCIN/OcapPOSS混合物的紫外光交联速率比两种纯组分要稍微低一点,纳米复合材料的玻璃化转变温度比纯PVCIN有所增加,这主要是由于POSS笼形结构对于聚合物基体的纳米增强作用。含有POSS的PVCIN纳米复合材料具有更好的热稳定性和阻燃性能。这主要是因为POSS笼形结构的引入使PVCIN基体的燃烧变得更加困难。2.含聚苯基倍半硅氧烷的环氧树脂复合材料的制备,形态结构和热力学性能将聚苯基倍半硅氧烷(PPSQ)加入到环氧树脂中来制备有机/无机复合材料。在制备过程中采用了两种不同的策略,得到了具有不同形态结构的两种复合材料。采用物理共混方式制备出的复合物,发生反应诱致的相分离。而通过加入催化剂来促进PPSQ与双酚A二缩水甘油醚(DGEBA)之间的反应,然后制备出的复合物则具有纳米结构。PPSQ和DGEBA之间的反应极大的抑止了PPSQ宏观相分离的发生。结果表明,当PPSQ含量一样时,纳米复合材料比相分离结构的复合材料具有更高的玻璃化转变温度。在PPSQ含量小于15wt%时,由于PPSQ微区的增强作用,纳米结构复合材料比相分离结构的复合材料具有更高的动态储能模量。有机/无机复合材料的热稳定性能和阻燃性能得到了很大提高。3.多面齐聚倍半硅氧烷封端的聚己内酯与α-环糊精超分子包合物的制备及研究本工作研究了多面齐聚倍半硅氧烷封端的聚己内酯PCL(POSS-capped PCL)与α-环糊精(α-CD)形成的超分子包结络合物(ICs)。用3-羟丙基七苯基POSS作为引发剂开环聚合己内酯(ε-CL)合成了不同分子量的POSS-capped PCL分子。因为PCL的一端存在体积巨大的POSS笼形结构,所以POSS-capped PCL与α-CD形成超分子络合物的时候,只能从PCL链段的自由一端进攻。结果表明有机/无机络合物具有隧道状结晶结构。在有机/无机络合物中不同组分的计量比是与POSS-capped PCL的分子量有关的。当POSS-capped PCL分子量较小时,络合效率降低。这主要是因为POSS笼形结构较难运动,限制了连接在POSS笼形结构上的PCL链段的运动性。当PCL链段较短时,这种影响更加明显。4.多面齐聚倍半硅氧烷封端的聚己内酯的熔融和结晶行为我们研究了不同PCL链段长度的POSS-capped PCL的熔融和结晶行为。POSS-capped PCL与纯PCL相比,平衡熔点升高。随之POSS含量的增加(或随着分子中PCL链段的减少),POSS-capped PCL的结晶速率常数和球晶生长速率随之增加。随着POSS含量的增加,POSS-capped PCL表面折叠自由能随之减少。这个结果可以归因于封端的POSS笼形结构在PCL链段结晶中所起的异相成核作用促进了PCL链段的结晶过程。5.环氧树脂/有机-无机两亲性分子的纳米结构热固性材料多面齐聚倍半硅氧烷封端聚己内酯(POSS-capped PCL)是用3-羟丙基七苯基POSS作为引发剂引发己内酯单体(ε-CL)开环聚合制备的。将这种新型的有机/无机两亲性分子加入到环氧树脂中制备具有纳米结构的热固性复合材料。结果表明随着POSS-capped PCL含量的不同,环氧树脂复合材料的结构从球形结构、蠕虫状结构到层状结构。纳米结构的形成是由于POSS-capped PCL两亲性分子的不同部分对于环氧树脂具有不同的相容性(PCL链段与固化前后的环氧树脂都是完全相容的,而POSS笼形结构与固化前后的环氧树脂都是不相容的。我们认为这种纳米结构的形成是按照自组装机制进行的。复合材料表面疏水性显著增加,表面自由能显著下降。材料表面性质的提高归因于POSS结构单元在环氧树脂复合材料表面的富集。

【Abstract】 Organic-inorganic nanocomposites have attracted considerable interest during the past few decades because they can exhibit unusual combinations of properties originating from the synergism of organic and inorganic components. Polyhedral oligomeric silsesquioxane (POSS) reagents, monomers, and polymers are emerging as a new chemical technology for nanoreinforced organic-inorganic hybrids. Polyhedral oligomeric silsesquioxanes (POSS) are a class of important nanosized cage-like molecules with a formula of [RSiO3/2]n, n = 6 ~12, where R can be various types of organic groups, one (or more) of which is reactive or polymerizable.In POSS technology, a diversity of polymerizable (or reactive) POSS macromers have been employed to copolymerize with organic monomer via the formation of covalent bonds between organic and inorganic components, in order to afford organic-inorganic nanostructured composites. The incorporation of the POSS nanocluster cages into polymeric materials can result in dramatic improvements in polymer properties, including mechanical properties, thermal stability, flame retardation, surface hydrophobicity, and melting and crystallization behavior etc.1. A Novel Photocrosslinkable Polyhedral Oligomeric Silsesquioxane and Its Nanocomposites with Poly(vinyl cinnamate) A novel photosensitive octacinnamamidophenyl polyhedral oligomeric silsesquioxane (OcapPOSS) was synthesized via the reaction between cinnamoyl chloride and octaaminophenyl polyhedral oligomeric silsesquioxane (OapPOSS). By initiating in situ UV photocrosslinking reaction of PVCIN in the presence of the photosensitive OcapPOSS, II is noted that the photocrosslinking rates of the PVCIN/POSS hybrids were slightly lower than those of the precursors, which could be ascribed to the nanoreinforcement of POSS cages on the polymer matrix. The glass transition temperatures (Tgs) of the nanocomposites were significantly higher than that of the control PVCIN. All the PVCIN nanocomposites containing POSS displayed the improved thermal stability. The high char yields of PVCIN nanocomposites also suggest improved flame retardence. It is plausible to propose that the improvement in weight retention is ascribed to the POSS constituent, which participated in the formation of the homogeneous hybrid network.2. Epoxy Resin Containing Polyphenylsilsesquioxane: Preparation, Morphology, and Thermomechanical PropertiesPolyphenylsilsesquioxanes (PSSQ) was used to incorporate into epoxy resin to prepare the organic-inorganic composites and two strategies were employed to afford the composites with different morphology. It is seen that the phase separation induced by polymerization occurred in the physical blending systems. However, the nanostructured composites were obtained while a catalytic amount Aluminum triacetylacetonate [Al(acac)3] was added to mediate the reaction between PPSQ and diglycidyl ether of bisphenol A (DGEBA). It is the inter-component reaction that significantly suppresses the phase separation on the micrometer scale. The organic-inorganic composites with different morphology displayed quite different thermomechanical properties. The nanostructured composites possessed higher glass transition temperatures (Tg’s) with the same loading of PPSQ although the inter-component reaction between PPSQ and DGEBA reduced the crosslinking density of epoxy matrix. It is the nanoreinforcement of PPSQ domains that afford the enhanced dynamic storage modulus for the nanostructured composites in comparison with the phase-separated composites with the PPSQ content less than 15 wt%. The organic-inorganic composites displayed the improved thermal stability and flame retardance.3. Supramolecular Inclusion Complexation of Polyhedral Oligomeric Silsesquioxane Capped Poly(e-caprolactone) with a-CyclodextrinThe supramolecular inclusion complexes involving polyhedral oligomeric silsesquioxane (POSS)-capped poly(ε-caprolactone) (PCL) andα-cyclodextrin (α-CD) were investigated. The POSS-terminated PCL with various molecular weights were prepared via the ring opening polymerization ofε-caprolactone with 3-hydroxypropylheptaphenyl POSS as an initiator. The POSS-capped PCLs were used to prepare the supramolecular inclusion complexes (ICs) withα-CD. Due to the presence of the bulky group (viz. POSS), the inclusion complexation betweenα-CD and the POSS-capped PCL is only carried out with single end of PCL chain threading inside the cavity ofα-CD. The results indicate that the organic-inorganic ICs have a channel-type crystalline structure. It is noted that the stoichiometry of the organic-inorganic ICs is quite dependent on the molecular weights of the POSS-capped PCL. When the PCL chains are shorter, the values of the stoichiometry are higher than 1:1 (CL unit :α-CD in mol). The deceased efficiency of inclusion complexation could be attributed to the lower mobility of the bulky POSS group, which restricted the motion of PCL chain attached to silsesquioxane cage. This effect is pronounced with decreasing the length of the PCL chains.4. Melting and Crystallization Behavior of Polyhedral Oligomeric Silsesquioxane (POSS)-terminated Poly(ε-caprolactone)We investigated the melting and crystallization behavior of POSS-capped PCL with various lengths of PCL chains. The novel organic-inorganic association result in the significant alterations in the melting and crystallization behavior of PCL. The POSS-capped PCL displayed the enhanced equilibrium melting points compared to the control PCL. Both the overall crystallization rate and the spherulitic growth rate of the POSS-terminated PCLs increased with increasing the concentration of POSS (or with decreasing length of PCL chain in the hybrids). It is found that the folding free energy of surface for the POSS-terminated PCLs decreased with increasing the concentration of POSS. These results could be ascribed to the effect of the favorable heterogeneous nucleation of POSS terminal groups, which accelerates the process of crystallization.5. Self-organized Thermosets from Epoxy Resin and Amphiphilic POSS-capped Poly( -caprolactone) MixturesPolyhedral oligomeric silsesquioxane (POSS)-capped PCL was synthesized via ring-open polymerization ofε-caprolactone with 3-hydroypropylheptaphenyl POSS as the initiator. The novel organic-inorganic amphiphile was used to incorporate into epoxy resin to prepare the nanostructured thermosets. It is found that depending on the concentration of the POSS-capped PCL in the composites, the POSS microdomains displayed the structures from spherical, wormlike to lamellar nanoobjects. The formation of the nanostructures in the epoxy thermosets was addressed on the basis of the miscibility and phase behavior of the sub-components (viz. POSS and PCL chains) of the organic-inorganic amphiphilic macromolecule with epoxy resin after and before curing reaction. It is judged that the formation of the nanostructures in the organic-inorganic hybrid composites follows the mechanism of self-assembly. The organic-inorganic nanocomposites displayed a significant enhancement in surface hydrophobicity as well as reduction in surface free energy. The improvement in surface properties was ascribed to the enrichment of POSS moiety on the surface of the nanostructured thermosets.

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