Chiral Conflict Leads to a New Relationship Between Temperature and Optical Activity

在化学系的有机动力学计划和材料研究部的聚合物计划的支持下，纽约理工大学的Mark Green教授将继续开展一项研究计划，以开发新的方法来控制温度和液晶光学性质之间的关系，这些关系是由于结构不同的对映体之间的竞争而产生的，目的是控制聚合物的螺旋感觉。将通过合成具有一对随机分散的侧基的螺旋形成聚合物来获得与上述液晶性质一致的材料，这些侧基具有对映体高度丰富但不同的结构，并且竞争控制聚合物的螺旋感觉。这是因为对于每个手性基团，有利于一个或另一个螺旋意义的自由能项的温度依赖性是不同的。基于统计物理理论，可以证明由合成确定的竞争手性基团的比例决定了螺旋感觉均匀分布的温度。由这种聚合物形成的溶致液晶产生了一系列材料，其中向列相将在唯一的预定温度下形成，而在该温度以上和低于该温度时，随着温度偏离向列相温度，将出现具有相反意义的螺距变紧的胆甾相。建议通过实验获得有关聚合物中分子内手性相互作用和衍生液晶中分子间手性相互作用的新信息。此外，最近的观察发现，含有适当荧光特性的染料的胆甾型溶致液晶可以产生激光，这为产生具有前所未有的温度依赖性和圆偏振特性的激光打开了可能性。化学系的有机化学和高分子化学计划以及材料研究部的聚合物计划支持纽约理工大学的Mark Green教授，他将尝试将多异氰酸酯的基本发现扩展到各种螺旋形成聚合物，包括聚乙炔、多肽和多肽核酸。这将涉及研究生的跨学科培训，涉及立体化学、聚合物化学、液晶和光学。结果可能会产生独特的想法，甚至是测量温度的设备，这是所有技术和生活的基础。由温度相关液晶产生的美丽颜色已经被展示给小学生，所以格林教授计划联系博物馆等组织来展示说明性的演示。这项工作将包括与新泽西州的一家初创公司、一家政府实验室、其他学术机构以及日本的科学家进行合作。

With the support of the Organic Dynamics Program in the Chemistry Division and the Polymer Program in the Division of Materials Research, Professors Mark Green at Polytechnic University of New York will continue a research program to develop new ways to control the relationship between temperature and the optical properties of liquid crystals that arise from the competition between structurally different enantiomers to control the helical sense of a polymer. A material consistent with the liquid crystal properties noted above will be obtained by synthesis of a helical forming polymer with a pair of randomly dispersed pendant groups that are enantiomerically highly enriched but of different structure and which are competing to control the helical sense of the polymer. This arises from the fact that the temperature dependence for the free energy term favoring one or the other helical sense differs for each of the chiral groups. Based on statistical physical theory it can be shown that the proportion of the competing chiral groups, determined by synthesis, fixes the temperature at which the helical senses are equally populated. Formation of lyotropic liquid crystals from such polymers yields a series of materials in which a nematic phase will be formed at a unique predetermined temperature while above and below this temperature cholesteric phases of opposite sense will arise with tightening pitch as the temperature deviates from the nematic temperature. Experiments are proposed to yield new kinds of information on intramolecular chiral interactions in the polymer and intermolecular chiral interactions in the derived liquid crystal. Moreover, the recent observation that cholesteric lyotropic liquid crystals with incorporated dyes of appropriate fluorescence characteristics give rise to lasing, opens the possibility of producing lasers with unprecedented temperature dependent and circular polarization properties..The Organic and Macromolecular Chemistry Program in the Chemistry Division and the Polymer Program in the Division of Materials Research supports Professor Mark Green at Polytechnic University of New York who will attempt to extend basic findings in polyisocyanates to a variety of helical forming polymers including polyacetylenes, peptides and peptide nucleic acids. This will involve the interdisciplinary training of graduate students, which will involve stereochemistry, polymer chemistry, liquid crystals and optics. The results may lead to unique ideas and even devices for measuring temperature, a property that is fundamental to all technology and life. The beautiful colors arising from the temperature dependent liquid crystals have been shown to intrigue elementary school students so Professor Green is planning to approach organizations such as museums to present explanatory demonstrations. The work will involve collaborations with a start-up company in New Jersey, a government laboratory, with scientists in other academic institutions and also in Japan.