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Axially Oriented Nanoporous Crystalline Phases of Poly(2,6-dimethyl-1,4-phenylene)oxide
ACS Applied Polymer Materials ( IF 4.4 ) Pub Date : 2020-06-30 , DOI: 10.1021/acsapm.0c00532
Manohar Golla 1 , Baku Nagendra 1 , Francesca Fierro 1 , Paola Rizzo 1 , Christophe Daniel 1 , Gaetano Guerra 1
Affiliation  

The aim of this paper is the achievement of films characterized by axially oriented nanoporous-crystalline (NC) and co-crystalline (CC) phases of poly(2,6-dimethyl-1,4-phenylene)oxide (PPO). Axially oriented films are generally suitable to determine host–guest relative orientations (by polarized IR spectra) and can facilitate the resolution of crystalline structures (by WAXD fiber patterns). This goal was achieved for the NC α form by using miscible blends of PPO with atactic polystyrene that exhibit reduced Tg and hence allow lower stretching temperatures (185–195 °C), thus avoiding formation of the dense mesomorphic γ form. Lower stretching temperatures also avoid loss of crystallinity (as proved by nearly unaltered melting enthalpies) and avoid polymer oxidation (as shown by the absence of the IR oxidation band at 1696 cm–1). Polarized IR spectra of axially oriented α and β form films allow establishment of directions of transition moment vectors of PPO vibrational bands, which are in agreement with those previously hypothesized on the basis of band relative intensities for films presenting different planar orientations. The sign of the IR linear dichroism of the 677 cm–1 benzene guest band allows establishing that benzene guest molecules are oriented with their molecular plane roughly parallel to the PPO crystalline chain axes.

中文翻译:

聚(2,6-二甲基-1,4-亚苯基)氧化物的轴向取向纳米多孔晶相

本文的目的是实现以聚(2,6-二甲基-1,4-亚苯基)氧化物(PPO)的轴向取向的纳米多孔晶体(NC)和共晶体(CC)相为特征的薄膜。轴向取向的薄膜通常适合于确定主客体的相对取向(通过偏振红外光谱),并且可以促进晶体结构的分辨(通过WAXD纤维图案)。通过使用PPO与无规立构聚苯乙烯的可混溶共混物(显示出较低的T g),可以实现NCα形式的这一目标。因此可以降低拉伸温度(185–195°C),从而避免形成致密的介晶γ形式。较低的拉伸温度还可以避免结晶度损失(几乎没有改变的熔融焓证明)和避免聚合物氧化(如1696 cm –1处不存在IR氧化带所示)。轴向取向的α和β型薄膜的偏振IR光谱可以确定PPO振动带的跃迁矩矢量的方向,该方向与先前根据具有不同平面取向的膜的带相对强度所假设的相一致。677 cm –1的红外线性二向色性征 苯客体带可以确定苯客体分子的分子平面大致平行于PPO晶链轴。
更新日期:2020-08-14
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