Processing, thermal stability and morphology of chiral sensing syndiotactic polystyrene films
Processing, thermal stability and morphology of chiral sensing syndiotactic polystyrene films
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DOI：
10.1039/b715269h
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发表时间：
2008-01
影响因子：
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通讯作者：
L. Guadagno;M. Raimondo;C. Silvestre;Ivano Immediata;Paola Rizzo;G. Guerra
中科院分区：
文献类型：
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作者：
L. Guadagno;M. Raimondo;C. Silvestre;Ivano Immediata;Paola Rizzo;G. Guerra
研究了适用于检测、放大和记忆几种挥发性非外消旋有机客体手性的δ型间规聚苯乙烯（s-PS）薄膜的制备条件。诱导圆二色性（ICD）现象的发生不仅严重依赖于纳米多孔δ相的存在，而且还依赖于用于膜制备的溶剂和工艺。ICD现象对客体对映体过量的依赖性也进行了研究。所观察到的ICD现象以及因此非外消旋客体分子的记忆不仅在手性客体去除之后而且在热处理至聚合物熔融温度（约270 °C）之后保持稳定。特别是，在向反式平面α晶相的热转变之后，仍然保持强烈的ICD现象，这表明手性记忆与某些分子结构无关，而是与非外消旋超分子结构的形成有关。这些超分子结构可能与仅在δ-型s-PS手性传感膜中观察到的大棒状微晶（通过原子力显微镜）有关。事实上，由于客体吸附，这些微晶明显地再结晶，然后对于至少高达240 °C的热处理保持基本上不变。
Processing conditions for the specific δ-form syndiotactic polystyrene (s-PS) films, being suitable to detect amplify and memorize the chirality of several volatile non-racemic organic guests, have been investigated. The occurrence of induced circular dichroism (ICD) phenomena is critically dependent not only on the presence of the nanoporous δ phase but also on the solvent and process used for the film preparation. The dependence of the ICD phenomena on the guest enantiomeric excess has also been studied. The observed ICD phenomena, and hence the memory of the non-racemic guest molecules, remain stable not only after chiral-guest removal but also after thermal treatments up to the polymer melting temperature (≈270 °C). In particular, the maintenance of intense ICD phenomena also after the thermal transition toward the trans-planar α crystalline phase indicates that the chiral memory is not associated with some molecular structure but with the formation of non-racemic supramolecular structures. These supramolecular structures could be possibly associated with the large rod-like crystallites observed only for δ-form s-PS chiral-sensing films (by atomic force microscopy). In fact, these crystallites are clearly re-crystallized, as a consequence of guest sorption, and then remain essentially unaltered for thermal treatments, at least up to 240 °C.