Spectroscopic Investigation of Guest-Guest Interactions in the Nanoporous-Crystalline δ and ε Forms of Syndiotactic Polystyrene
Spectroscopic Investigation of Guest-Guest Interactions in the Nanoporous-Crystalline δ and ε Forms of Syndiotactic Polystyrene
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DOI：
10.1021/jp502679d
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发表时间：
2014-06-05
影响因子：
3.7
通讯作者：
Guerra, Gaetano
中科院分区：
文献类型：
--
作者：
Albunia, Alexandra R.;Guerra, Gaetano
共晶聚合物样品中主客体相互作用的研究通常是复杂的，因为它们可能出现在非晶相和结晶相中。在本文中，我们证明了轴向取向薄膜的极化FTIR光谱允许区分空间有序和无序的客体氢键，分别发生在晶体和非晶聚合物相中。特别是，对羟基苯甲酸（对羟基苯甲酸酯，相关抗菌分子）的烷基酯在s-PS膜中吸收时可能形成的氢键，表现为纳米多孔晶单斜三角相和正交相。x射线衍射图显示，在高来宾吸收下，形成了三斜三角形和正交型的共晶形式。红外线性二色性测量表明，在δ型薄膜中，对羟基苯甲酸酯作为孤立的客体存在于晶体形式的空腔中，而对羟基苯甲酸酯之间的客体氢键仅在非晶相中观察到。对epsilon形式薄膜的类似测量表明，相反，客体氢键主要发生在晶体相的通道中，客体分子平面大致平行于聚合物主螺旋轴。
The study of guest-guest interactions in cocrystalline polymer samples is in general complicated by their possible occurrence in both amorphous and crystalline phases. In this paper we show that polarized FTIR spectra of axially oriented films allow discrimination between spatially ordered and disordered guest guest hydrogen bonds occurring in crystalline and amorphous polymer phases, respectively. In particular, the possible formation of hydrogen bonds between alkyl-esters of para-hydroxybenzoic acid (parabens, relevant antimicrobial molecules), when absorbed in s-PS films exhibiting nanoporous-crystalline monoclinic delta and orthorhombic epsilon phases, has been studied. X-ray diffraction patterns show the formation, for high guest uptake, of triclinic delta and orthorhombic epsilon cocrystalline forms. Infrared linear dichroism measurements show that for delta form films the parabens are present as isolated guests of the cavities of the crystalline form, while guest guest hydrogen bonds between parabens are observed only in the amorphous phase. Analogous measurements for epsilon form films show that, on the contrary, guest guest hydrogen bonds occur prevailingly in the channels of the crystalline phase, with guest molecular planes being roughly parallel to the polymer host helical axes.