Reaction Engineering of Covalent Adaptable Polymer Networks

鲍曼：该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。交联热固性聚合物的形成在我们的社会中无处不在，应用于涂料，粘合剂，复合材料，牙科材料和快速成型。不幸的是，相同的交联结构是许多理想的机械和热性能的起源，导致聚合物的形状和性能在聚合时被固定，传统上需要降解交联来改变它们。此外，聚合过程本身会导致显著的应力发展，最终导致翘曲、材料失效，并需要复杂的固化工艺。PI计划开发聚合单体，形成一种称为共价适应性网络（can）的新材料类别。这些材料结合了共价网络的优势特性和根据需要逆转聚合物网络结构的能力。一旦这些网络形成，他将展示和理解通过聚合物网络中受控反应的后续适应性可以实现的各种特性，这些特性可以通过均匀或有图案的暴露在光下、温度变化或暴露在电磁场中触发。聚合物材料具有适应性，能够通过控制应力、形状、塑性和复合组织来“按需”响应，这对粘合剂、热固性复合材料、生物材料、聚合物涂层和超材料的发展至关重要。PI计划通过这种外部可触发can的合成、表征和开发来扩展交联聚合物网络的能力。这些进步是通过开发材料和工艺来实现的，这些材料和工艺可以在暴露于热、光或电磁场时实现聚合、网络可逆性、流动、形状记忆、裂纹愈合和复合组织。本研究计划分为四个主要目的：(i)设计和合成含有烯丙基硫化物（AS）的新功能单体，以便将基于AS的适应性网络的优势扩展到更广泛的传统热固性材料；（ii）合成基于Diels-Alder （DA）的多功能聚合物网络，其中聚合和可逆交联的形成通过暴露于电磁场来控制，无论是在聚合的同时还是在聚合之后；（iii）开发和优化反应条件，从基于数据的聚合物网络中形成图案复合超材料结构；（iv）将上述研究作为培养至少10名本科生和4名研究生的多样化群体的手段，在发现学习过程中以及在聚合物科学和反应工程领域。在超材料制造、可逆聚合物网络设计和远程控制聚合物网络结构方面，将会出现变革性的发现。这些目标的实现可能会带来进步，为未来的技术发展奠定基础。具体来说，这项研究将建立一系列新的可用交联材料和反应方法，适用于形成广泛的聚合物网络结构。这些网络对于确定交联聚合物的基本结构是有价值的，因为网络的微观和宏观性质都是可控的。还将开发新的技术来减少聚合引起的收缩应力。聚合动力学的耦合、高度局域热传递和粒子的布朗运动是超材料形成所必需的，这将产生重大的智力进步。更广泛的影响通过提供一种可逆控制聚合后交联网络的形状、应力和应变的方法，开发这种新型聚合物材料有助于克服交联聚合物的问题。通过迟滞加热，人们将能够远程消除结构热固性材料和复合材料中的疲劳并促进裂纹愈合，而基于da的can的图案暴露将使复杂的3D复合材料能够形成几乎无限可能的材料特性。在结构粘合剂、3D原型、MEMS、牙科材料、光学材料和复合材料等各种工艺中的应用都可以从这项工作的成功完成中受益。受研究影响的研究生的数量和多样性将通过与PI目前指导的教育部GAANN项目的互动而得到提高。本科生将通过独立研究项目和获得本科生资助的研究经历直接参与研究。

0933828BowmanThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The formation of crosslinked thermosetting polymers is ubiquitous in our society in applications such as coatings, adhesives, composite materials, dental materials and rapid prototyping. Unfortunately, the same crosslinked structure that is the origin of many of the desirable mechanical and thermal properties results in the polymer shape and properties being fixed upon polymerization, traditionally requiring degradation of the crosslinks to change either. Additionally, the polymerization process itself leads to significant stress development and ultimately warping, material failure, and the requirement of complex curing processes. The PI plans to develop monomers that polymerize to form a new material class referred to as Covalent Adaptable Networks (CANs). These materials combine the advantageous properties of covalent networks with the ability to reverse the polymer network structure on demand. Once these networks are formed, he will demonstrate and understand the various properties that can be achieved by subsequent adaptation through controlled reactions within the polymer network, as triggered either by uniform or patterned exposure to light, by temperature changes, or by exposure to an electromagnetic field. Polymeric materials such as these that are adaptable and able to respond 'on demand' with control of stress, shape, plasticity and composite organization are critical to the development of adhesives, thermosetting composite materials, biomaterials, polymeric coatings, and metamaterials. The PI plans to expand the capabilities of crosslinked polymer networks by this synthesis, characterization, and development of externally triggerable CANs. These advances are achieved by developing materials and processes that enable polymerization, network reversibility, flow, shape memory, crack healing, and composite organization upon exposure to heat, light, or electromagnetic fields. This research program is divided into four principal aims: (i) Design and synthesize new functional monomers that contain allyl sulfides (AS) so that the benefits of AS-based adaptable networks are expanded to a broader range of conventional thermosets, (ii) Synthesize multifunctional Diels-Alder (DA)-based polymer networks in which the polymerization and reversible crosslink formation are controlled by exposure to an electromagnetic field, either concurrent with or after the polymerization, (iii) Develop and optimize reaction conditions to form patterned composite metamaterial structures from the DA-based polymer networks, and (iv) Use the aforementioned research as a means for training a diverse group of at least 10 undergraduate students and 4 graduate students in the discovery learning process and in the fields of polymer science and reaction engineering. Transformational discoveries will occur in regards to metamaterials fabrication, reversible polymer network design, and remotely controllable polymer network structures. Intellectual MeritThe achievement of these goals could lead to advances that provide a foundation for future technology developments. Specifically, this research will establish a new range of available crosslinked materials and reaction methodologies that are appropriate for the formation of a wide range of polymer network structures. These networks will be valuable in ascertaining the fundamental structure of crosslinked polymers, as both the microscopic and macroscopic nature of the network are controllable. New techniques will also be developed to reduce polymerization induced shrinkage stress. The coupling of polymerization kinetics, highly localized heat transfer, and Brownian motion of particulates as necessary for metamaterial formation will yield significant intellectual advances. Broader ImpactDeveloping this new class of polymeric materials helps to overcome a problem with crosslinked polymers by providing a means for reversibly controlling the shape, stress, and strain of crosslinked networks post-polymerization. With the hysteresis heating, one will be able to remotely eliminate fatigue and facilitate crack healing in structural thermosets and composites and the patterned exposure of the DA-based CANs will enable complex 3D composites to be formed with an almost infinite array of possible material properties. Applications in processes as varied as structural adhesives, 3D prototyping, MEMS, dental materials, optical materials and composite materials all could benefit from the successful completion of this work. The number and diversity of the graduate students impacted by the research will be heightened by interaction with the Department of Education GAANN program that the PI currently directs. Undergraduate students will participate directly in the research through independent study projects and research experiences for undergraduate grants.