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首页> 外文学位 >Characterization of the thermodynamics and deformation behavior of styrene-butadiene-styrene grafted with polyhedral oligomeric silsesquioxanes.
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Characterization of the thermodynamics and deformation behavior of styrene-butadiene-styrene grafted with polyhedral oligomeric silsesquioxanes.

机译：多面体低聚倍半硅氧烷接枝的苯乙烯-丁二烯-苯乙烯的热力学和变形行为的表征。

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This research study uses a model nanostructure-copolymer system in order to develop a fundamental understanding of how polymers are affected by functionalized nanostructures. For this study, polyhedral oligomeric silsesquioxanes (POSS) was chosen as the model nanostructure and polystyrene-block-polybutadiene-block-polystyrene copolymer (SBS) as the model polymer host. The choice of materials and chemical reaction scheme for grafting the SBS-POSS copolymers allows for reproducible products with the opportunity for wide selection of nanostructure grafting fractions.; In order to examine the effects that the nanostructure's electronic properties have on the host polymer, the organic group of the POSS nanostructures was varied. To facilitate a rigorous comparison, four sterically similar, yet electronically different POSS derivatives were selected (cyclopentyl (Cp), cyclopenyl (Cy), cyclohexenyl (Cye), and phenyl (Ph)). Ph-POSS results in the greatest changes relative to the ungrafted SBS block copolymer because its chemistry has the largest contrast to the block in which it is grafted while simultaneously having the largest affinity toward the ungrafted block.; All four of the cyclic POSS were found to have some affinity toward the polystyrene phase, so iBu-POSS was investigated in order to observe the effects of incorporating a noninteracting nanostructure. Two host morphologies were examined in order to compare noninteracting (iBu) and strongly interacting (Ph) POSS nanostructures. The morphology and phase behavior observed for noninteracting POSS is consistent with simply changing polystyrene content with no noticeable change in chi. Furthermore, local and long-ranged order of the morphology is well-preserved. The interacting nanostructures reduce chi substantially and disrupt the local order of the morphology, which is equivalent to a compatibilizing effect.; Deformation was studied to supplement the previous findings regarding the equilibrium morphology, and give further information on the nature of the interactions between POSS-polymer and POSS-POSS interactions. The mechanical properties for both the grafted copolymers inherently drop because nanostructure grafting reduces the polystyrene content. For the noninteracting iBu-POSS, the reduction in mechanical properties was consistent with the fraction of polystyrene because the nanostructures are noninteracting with the polystyrene block and do not qualitatively change the morphology. This was observed at both low (30°C) and high (70°C) temperatures. The interacting Ph-POSS behavior is more complex. With increasing Ph-POSS, the morphology becomes more disrupted which should result in an additional drop in mechanical properties. However, there is reinforcement at larger concentrations of Ph-POSS. The disrupted morphology of the 10% and 20% Ph-POSS results in a smaller grain size, which together with the presence of POSS crystallites reinforce, or network, the morphology. Low strain reinforcement is more prominent at lower temperatures. At high temperatures (but still below Tg,PS), the drop in mechanical properties from the disrupted morphology order outweighs the low strain reinforcement effects. Some reinforcement is still observed at these higher temperatures due to POSS-POSS effects.
机译：这项研究使用模型纳米结构-共聚物系统，以发展对聚合物如何受到功能化纳米结构影响的基本理解。对于本研究，选择多面体低聚倍半硅氧烷（POSS）作为模型纳米结构，选择聚苯乙烯-嵌段-聚丁二烯-嵌段-聚苯乙烯共聚物（SBS）作为模型聚合物主体。用于接枝SBS-POSS共聚物的材料和化学反应方案的选择允许可再现的产物，并具有广泛选择纳米结构接枝组分的机会。为了检查纳米结构的电子性质对主体聚合物的影响，改变了POSS纳米结构的有机基团。为了进行严格的比较，选择了四个空间相似但电子上不同的POSS衍生物（环戊基（Cp），环戊烯基（Cy），环己烯基（Cye）和苯基（Ph））。相对于未接枝的SBS嵌段共聚物，Ph-POSS的变化最大，这是因为其化学性质与接枝的嵌段的反差最大，同时对未接枝的嵌段的亲和力最大。发现所有四个环状POSS对聚苯乙烯相都有一定的亲和力，因此对iBu-POSS进行了研究，以观察掺入非相互作用纳米结构的影响。为了比较非相互作用（iBu）和强相互作用（Ph）POSS纳米结构，检查了两种宿主形态。对于非相互作用的POSS，观察到的形态和相行为与简单地改变聚苯乙烯含量而没有明显的chi变化相一致。此外，形态的局部和远距离顺序被很好地保留。相互作用的纳米结构显着降低了chi并破坏了形态的局部顺序，这相当于增容作用。对变形进行了研究，以补充有关平衡形态的先前发现，并提供有关POSS-聚合物与POSS-POSS相互作用之间相互作用的性质的进一步信息。两种接枝共聚物的机械性能都会固有地下降，因为纳米结构接枝会降低聚苯乙烯的含量。对于非相互作用的iBu-POSS，机械性能的下降与聚苯乙烯的比例一致，这是因为纳米结构与聚苯乙烯嵌段不相互作用并且不会定性地改变形态。在低温（30°C）和高温（70°C）均可观察到。相互作用的Ph-POSS行为更为复杂。随着Ph-POSS的增加，形态变得更加混乱，这将导致机械性能的进一步下降。但是，在较大浓度的Ph-POSS中会增强。 10％和20％的Ph-POSS的形态被破坏会导致晶粒尺寸变小，再加上POSS晶粒的存在会增强或形成网络。在较低温度下，低应变增强更为突出。在高温下（但仍低于Tg，PS），破坏形态的机械性能下降超过了低应变增强效应。由于POSS-POSS效应，在这些较高的温度下仍观察到一些增强作用。

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