Collapse of stiff conjugated polymers with chemical defects into ordered, cylindrical conformations
Collapse of stiff conjugated polymers with chemical defects into ordered, cylindrical conformations
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DOI：
10.1038/35016520
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发表时间：
2000-06-29
期刊：
影响因子：
64.8
通讯作者：
Barbara, PF
中科院分区：
文献类型：
--
作者：
Hu, DH;Yu, J;Barbara, PF
由聚合物链组成的合成和生物材料的光学、电子和机械性质敏感地取决于这些链所采用的构象。因此，这些系统可用的构象范围具有强烈的基本（1，2）以及实际（3-6）兴趣，并且已经预测了不同的构象类别，这取决于聚合物链的刚度和链内链段之间的吸引力相互作用的强度（7-10）。例如，柔性聚合物应采用高度无序的构象，类似于无规卷曲，或者在存在强链内吸引力的情况下，类似于所谓的“熔融球”（2，10）。相比之下，具有强链内相互作用的刚性聚合物预计会塌陷成具有长程有序的构象，呈环状或棒状结构（8，9，11）。在这里，我们使用计算机模拟表明，从偏振光谱测量获得的各向异性分布的个别聚[2-甲氧基-5-（2 '-乙基己基）氧基-1，4-phenylenevinylene]聚合物分子是一致的，这种原型的刚性共轭聚合物采用高度有序的，塌陷的构象，不能与理想的环形或棒结构。我们发现，存在所谓的“四面体化学缺陷”，其中共轭碳-碳键被四面体键取代，将聚合物链分成结构上可识别的准直链段，使分子采用圆柱形构象。事实上，高度有序的圆柱形构象可能是决定共轭聚合物非凡的物理性质的关键因素，包括高效的分子内能量转移和薄膜中显着的局部光学各向异性。
The optical, electronic and mechanical properties of synthetic and biological materials consisting of polymer chains depend sensitively on the conformation adopted by these chains. The range of conformations available to such systems has accordingly been of intense fundamental(1,2) as well as practical(3-6) interest, and distinct conformational classes have been predicted, depending on the stiffness of the polymer chains and the strength of attractive interactions between segments within a chain(7-10). For example, flexible polymers should adopt highly disordered conformations resembling either a random coil or, in the presence of strong intrachain attractions, a so-called 'molten globule'(2,10). Stiff polymers with strong intrachain interactions, in contrast, are expected to collapse into conformations with long-range order, in the shape of toroids or rod-like structures(8,9,11). Here we use computer simulations to show that the anisotropy distribution obtained from polarization spectroscopy measurements on individual poly[2-methoxy-5-(2'-ethylhexyl)oxy-1,4-phenylenevinylene] polymer molecules is consistent with this prototypical stiff conjugated polymer adopting a highly ordered, collapsed conformation that cannot be correlated with ideal toroid or rod structures. We rnd that the presence of so-called 'tetrahedral chemical defects', where conjugated carbon-carbon links are replaced by tetrahedral links, divides the polymer chain into structurally identifiable quasi-straight segments that allow the molecule to adopt cylindrical conformations. Indeed, highly ordered, cylindrical conformations may be a critical factor in dictating the extraordinary photophysical properties of conjugated polymers, including highly efficient intramolecular energy transfer and significant local optical anisotropy in thin films.