Characterization of polymer structures based on Burnside's lemma.
Characterization of polymer structures based on Burnside's lemma.
复制标题
DOI：
10.1103/physreve.84.011805
复制
发表时间：
2011-07
期刊：
影响因子：
--
通讯作者：
K. Doi;Keigo Kato;S. Kawano
中科院分区：
文献类型：
--
作者：
K. Doi;Keigo Kato;S. Kawano
聚合物结构建模是近年来材料科学的一个发展趋势。计算科学和纳米技术的发展使预测复杂分子结构的性质成为可能。许多理论和计算方法已经成功地阐明了聚合物结构的性质。依靠计算机能力对整个复杂结构进行建模并不总是最好的。材料的重要特性可以在简单的结构方面表现出来。在本研究中，通过将Burnside引理应用于建模过程来研究聚合物结构的特性。该方法有望用于模拟官能团在表达其功能方面起重要作用的聚合物或分子晶体。完整地计算了对称和周期性下的每一个结构，从而澄清了官能团构象引起的能量分布。介绍了该方法的具体步骤，并将其应用于磺化聚醚醚酮（SPEEK）分子结构的研究。SPEEK专注于聚合物电解质燃料电池中质子交换膜的候选材料。磺酸基在质子交换膜中形成质子传导通道具有重要作用。从我们的分析中发现，在稳定的条件下，磺酸基倾向于分散在SPEEK膜中。对于质子交换膜来说，这些都是不利的特性，因为它们难以形成理想的水通道，这对于高质子电导率是不可避免的。这是SPEEK膜不如Nafion膜的一个原因，Nafion膜作为质子交换膜表现出最高的性能。利用本方法，验证了以往报道的实验和理论结果，并从结构简单性的角度讨论了详细的特性。
Polymer structure modeling is a trend of recent material sciences. Developments of computational science and nanotechnology make it possible to predict properties of complicated molecular structures. Many theoretical and computational methods have succeeded in elucidating the nature of polymer structures. It is not always best to model whole complicated structures depending on computer capabilities. Significant properties of materials may be manifested in simple structural aspects. In the present study, characteristics of a polymer structure are investigated by applying Burnside's lemma to the modeling procedure. This method is expected to be available to model polymers or molecular crystals in which functional groups play an important role in expressing their functions. Every structure under the symmetry and periodicity is counted completely and the energy distribution caused by the conformations of functional groups can be clarified. The detailed procedure is introduced and the present method is applied to a problem for investigating molecular structures of sulfonated poly(ether ether ketone) (SPEEK). SPEEK is focused on a candidate for proton exchange membranes in polymer electrolyte fuel cells. Sulfonic groups have a significant role in proton exchange membranes to make proton conduction channels. From our analysis, it is found that sulfonic groups tend to be dispersed in SPEEK membranes at their stable conditions. These are unfavorable characteristics for proton exchange membranes due to their difficulty to form desirable water channels inevitable for the high proton conductivity. This is one reason why SPEEK membranes are inferior to Nafion® membranes that express the highest performance as proton exchange membranes. Using the present method, experimental and theoretical results previously reported are confirmed and detailed characteristics are discussed in terms of structural simplicities.