Development and Study of Structurally-Dynamic Covalent Polymers

结构动态共价聚合物的开发与研究

• 批准号: 1609076
• 负责人: Stuart Rowan
• 金额: $ 43.44万
• 依托单位: University of Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2021-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1609076&HistoricalAwards=false
• 关键词: Development; Study; Structurally; Dynamic; Covalent

PART 1: NON-TECHNICAL SUMMARYTraditional polymers or plastics have been designed to minimize degradation (e.g. by breaking of covalent bonds) and as such maintain their mechanical properties over their lifetime. This has led to a wide range of very useful materials (such as fibers, plastics and adhesives) that are ubiquitous in our daily lives. One issue with such materials is that when they break or degrade it can be difficult and/or not cost effective to repair or recycle them. What if plastics could be accessed that would allow them to either heal scratches or deformations or to be more efficiently recycled. One way to achieve this is to design into the polymer structure reversible bonds that can be broken and remade upon application of a relatively small amount of heat or light. With this NSF funding the Rowan group is working on a range of different stimuli-responsive reversible bonds that will be incorporated into polymers and used to access new classes of responsive/adaptive materials. A key component of these systems is the ability to systematically control the stimulus required to access the reversible character of the bond which in turn allows them to be tailored for different applications. With these materials the Rowan group will focus on the development of (1) new soft actuators that act like 'polymeric muscles' and offer applications to (soft) robotics, (2) materials that exhibit both scratch-healing characteristics as well as enhanced toughness to extend their useful operational lifetime, and (3) on-demand reversible glues and adhesives. This project involves graduate and undergraduate students, students from local high schools, including students from underserved and predominately minority neighborhoods of Chicago. The integrated approach of this project provides students at all levels with an exciting learning environment and broad research experiences. In addition, Prof. Rowan and his research group will design new hands-on demonstrations for a Museum outreach program entitled "Nature's Materials", which is part of the Cleveland Museum of Natural History's "Winter Discovery Day" on Dr. Martin Luther King Jr. Day. This program aims (i) to expose the local community to polymers and how Nature's materials can help us create a sustainable planet, and (ii) to train current graduate students on how to communicate to and educate the general public and younger students about science and technology.PART 2: TECHNICAL SUMMARYThe introduction of dynamic bonds (that can undergo reversible exchange) into a polymer network imparts new adaptive properties onto the materials. The adaptive properties come from the network's ability to alter its architecture (and/or composition) through dynamic bond exchange and as such have been termed structurally-dynamic polymers. Depending on the specific type, placement and amount of the dynamic bond incorporated into the network the resulting films will have the ability to be re-processable/re-moldable, exhibit healing and/or shape-memory properties, and even open the door to materials that have enhanced toughness, stress relaxation, and/or adaptive adhesion capabilities. This proposal outlines the synthetic as well as structural (via NMR, MALDI-MS, FT-IR, UV, POM and WAXS/SAXS) and mechanical (rheology, tensile testing, and dynamic mechanical thermal analysis) studies on three different classes of structurally-dynamic polymers, focusing not only on investigating the basic science of these systems but also on targeting specific applications that suit the specific dynamic behavior of the film's chemistry. Specifically, the Rowan group will focus on the synthesis, characterization, and investigation of (1) poly(disulfides), (2) thia-Michael adduct-containing polymers and (3) poly(alkylureas). While poly(disulfides) networks are known and have been investigated as healable materials, their use to access photo-adaptive liquid crystalline elastomers is new. Specific interest is in accessing 3D actuating films with this class of material. The thia-Michael reaction can be dynamic at room temperature, but to date, this class of dynamic bond has received little attention in the polymer field. The advantage of this bond is that both its exchange thermodynamics and kinetics can be systematically altered by changing the electronics of the alkene (Michael acceptor). The final class of dynamic bond the PI will investigate is the most commercially relevant and is based on bulky alkylureas. Alkylureas are used as blocked (protected) isocyanates in the polyurethane industry that deblock at temperatures 100°C. The PI will target/develop alkylureas and derivatives that can deblock at lower temperatures. The goal for these last two classes of materials is to develop structure/property relationships focusing on their solid state mechanical and adaptive properties.

第 1 部分：非技术摘要传统聚合物或塑料的设计目的是最大限度地减少降解（例如，通过共价键的断裂），并因此在其使用寿命内保持其机械性能。这催生了我们日常生活中无处不在的各种非常有用的材料（例如纤维、塑料和粘合剂）。此类材料的一个问题是，当它们破裂或降解时，修复或回收它们可能很困难和/或不具有成本效益。如果塑料能够治愈划痕或变形，或者更有效地回收，会怎样呢？实现这一目标的一种方法是在聚合物结构中设计可逆键，这些键可以在施加相对少量的热或光时断裂和重建。在国家科学基金会的资助下，罗文小组正在研究一系列不同的刺激响应可逆键，这些键将被纳入聚合物中并用于获得新型响应/自适应材料。这些系统的一个关键组成部分是能够系统地控制获得键的可逆特性所需的刺激，从而使它们能够针对不同的应用进行定制。通过这些材料，罗文小组将重点开发（1）新型软执行器，其作用类似于“聚合物肌肉”，并为（软）机器人提供应用；（2）具有划痕修复特性和增强韧性以延长其使用寿命的材料；（3）按需可逆胶水和粘合剂。该项目涉及研究生和本科生、当地高中的学生，包括来自芝加哥服务水平低下和以少数族裔为主的社区的学生。该项目的综合方法为各个级别的学生提供了令人兴奋的学习环境和广泛的研究经验。此外，罗文教授和他的研究小组将为题为“自然的材料”的博物馆外展项目设计新的实践演示，该项目是克利夫兰自然历史博物馆马丁·路德·金博士纪念日“冬季发现日”的一部分。 该计划的目的是 (i) 让当地社区接触聚合物以及大自然的材料如何帮助我们创造一个可持续发展的地球，以及 (ii) 培训在校研究生如何与公众和年轻学生进行沟通和教育科学技术。第 2 部分：技术摘要将动态键（可以进行可逆交换）引入聚合物网络，赋予材料新的适应性。适应性特性来自网络通过动态键交换改变其结构（和/或组成）的能力，因此被称为结构动态聚合物。根据纳入网络的动态键的具体类型、位置和数量，所得薄膜将具有可再加工/可再成型的能力，表现出愈合和/或形状记忆特性，甚至为具有增强韧性、应力松弛和/或自适应粘附能力的材料打开了大门。该提案概述了三种不同类别的结构动态聚合物的合成和结构（通过 NMR、MALDI-MS、FT-IR、UV、POM 和 WAXS/SAXS）和机械（流变学、拉伸测试和动态机械热分析）研究，不仅侧重于研究这些系统的基础科学，而且还针对适合薄膜特定动态行为的特定应用。 化学。具体来说，罗文小组将重点关注（1）聚（二硫化物）、（2）含硫杂-迈克尔加合物的聚合物和（3）聚（烷基脲）的合成、表征和研究。虽然聚（二硫化物）网络是已知的，并且已经作为可修复材料进行了研究，但它们用于获得光自适应液晶弹性体的用途是新的。 特别感兴趣的是使用此类材料访问 3D 驱动电影。硫杂-迈克尔反应在室温下可以是动态的，但迄今为止，这类动态键在聚合物领域很少受到关注。这种键的优点是可以通过改变烯烃（迈克尔受体）的电子来系统地改变其交换热力学和动力学。 PI 将研究的最后一类动态键是最具商业相关性的，并且基于大烷基脲。烷基脲在聚氨酯工业中用作封端（受保护）异氰酸酯，可在 100°C 温度下解封端。 PI 将瞄准/开发可在较低温度下解封闭的烷基脲和衍生物。最后两类材料的目标是开发结构/性能关系，重点关注其固态机械和适应性性能。