Design, Synthesis and Investigation of Substitution on Conformation Properties

在这个由化学系化学结构、动力学机制-B项目资助的项目中，加州大学默塞德分校的Jennifer Lu教授正在开发一类新的分子开关，这种开关可以由低能量刺激触发。受生物分子形状持久而精确变化的启发，卢教授设计并合成了一套独特的分子结构，并研究它们不断变化的结构。该项目的多学科性质采用了有机化学，物理化学和材料科学与工程的基础知识，并提供了一个有利于培养和激励各级学生的学习环境。该教育计划的一个关键组成部分是鼓励高中生在STEM领域接受大学教育。这项研究可能有助于科学家了解植物对阳光的定向生长以及如何收集废物能量。Lu教授和她的研究小组开发了能够产生巨大热收缩（高达-2300 ppm/K）的聚合物。 这些聚合物含有少量的1，4，7，10四苯基酰胺取代的s-二苯并环辛烷（DBCOD），一个灵活的环辛烷基团在每个末端稠合到一个刚性苯环上。该研究小组假设这种热收缩源于DBCOD从全局最小值到局部最小值的构象上转换。 这两种构象的相对能量和这种构象转变的能垒可以通过局部环境（例如，替代类型和模式）。为了获得对DBCOD构象变化的热力学和动力学方面的取代基效应的基本理解，他们进行了多学科的研究，包括计算指导的模型系统合成和原子和分子尺度的表征。 这个项目的目标是建立取代设计规则，将特定的取代基与它们对构象性质的影响联系起来。 为了将原子尺度的变化与宏观行为联系起来，并验证设计准则，他们使用了DBCOD衍生物，该衍生物在较低温度下有利于扭曲船构象，在较高温度下有利于椅子构象，以制造线性聚合物。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

In this project, funded by the Chemical Structure, Dynamics & Mechanisms-B Program of the Chemistry Division, Professor Jennifer Lu at University of California, Merced, is developing a new class of molecular switches that can be triggered by low-energy stimuli. Inspired by long-lasting and precise changes in the shapes of biomolecules, Professor Lu designs and synthesizes a set of unique molecular structures and studies their changing structures. The multidisciplinary nature of this project employs fundamental knowledge from organic chemistry, physical chemistry and materials science and engineering, and provides a learning environment that is conducive to training and inspiring students at all levels. A key component of the education program involves outreach to encourage high school students to pursue college education in STEM fields. This research may help scientists understand the directional growth of a plant in response to sunlight and how to harvest waste energy. Professor Lu and her research group develope polymers that generate anomalously large thermal contractions (up to -2300 ppm/K). These polymers contain a small amount of 1, 4, 7, 10 tetra-phenylamide substituted s-dibenzocyclooctadiene (DBCOD), a flexible cyclooctane group fused to one rigid phenyl ring at each end. The research group hypothesizes that this thermal contraction stems from DBCOD's conformational up-conversion from the global minimum to a local minimum. The relative energies of these two conformers and the energy barriers of this conformational transition can be adjusted by the local environment (e.g., substitution type and pattern). To acquire a fundamental understanding of substituent effects on the thermodynamic and kinetic aspects of the DBCOD conformational change, they conduct a multidisciplinary investigation that involves computation-guided model system synthesis and atomic and molecular scale characterizations. The goal of this project is to establish substitution design rules that correlate specific substituents to their effects on conformation properties. To connect atomic-scale changes to macroscopic behavior and validate the design guideline, they use the DBCOD derivative that favors the twist-boat conformation at lower temperature and the chair conformation at higher temperature to make a linear polymer.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.