Reaction Engineering of Covalent Adaptable Polymer Networks

0933828Bowman该奖项由2009年美国复苏和再投资法案(公共法律111-5)资助。在涂料、粘合剂、复合材料、牙科材料和快速成型等应用中，交联型热固性聚合物的形成在我们的社会中普遍存在。不幸的是，作为许多期望的机械和热性能的来源的相同的交联结构导致聚合物的形状和性质在聚合时被固定，传统上需要交联物的降解才能改变其中的任何一种。此外，聚合过程本身会导致显著的应力发展和最终翘曲、材料失效以及复杂固化过程的要求。PI计划开发聚合单体，形成一种新的材料类别，称为共价适配网络(CANS)。这些材料结合了共价网络的有利性质和按需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内的受控反应实现的后续适应的各种特性，如由均匀或图案化的光暴露、温度变化或暴露在电磁场中触发。这样的聚合物材料能够适应并能够根据需要控制应力、形状、塑性和复合材料组织，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计划通过合成、表征和开发外部可触发的罐头来扩展交联聚合物网络的能力。这些进展是通过开发材料和工艺来实现的，这些材料和工艺能够在暴露于热、光或电磁场的情况下实现聚合、网络可逆性、流动性、形状记忆、裂纹愈合和复合材料组织。该研究计划分为四个主要目标：(I)设计和合成含有烯丙基硫化物(AS)的新的功能单体，以使基于AS的适应性网络的益处扩展到更广泛的传统热固性树脂，(Ii)合成基于DA的多功能聚合物网络，其中聚合和可逆交联链的形成通过暴露在电磁场中来控制，同时或在聚合之后，(Iii)开发和优化反应条件，以从基于DA的聚合物网络形成图案化的复合超材料结构，以及(4)利用上述研究作为一种手段，在发现学习过程以及聚合物科学和反应工程领域对至少10名本科生和4名研究生进行培训。在超材料制造、可逆聚合物网络结构和远程可控聚合物网络结构方面将出现变革性的发现。智力价值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。具体地说，这项研究将建立一系列新的可用的交联材料和反应方法，适合于形成广泛的聚合物网络结构。这些网络在确定交联聚合物的基本结构方面将是有价值的，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降低聚合引起的收缩应力。聚合动力学、高度局域热传递和颗粒的布朗运动的耦合是形成超材料所必需的，这将带来重大的智能进步。更广泛的影响开发这种新型聚合物材料通过提供一种方法来可逆地控制聚合后交联网络的形状、应力和应变，从而帮助克服交联聚合物的问题。通过滞后加热，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，基于DA的罐头的图案化暴露将使复杂的3D复合材料能够形成几乎无限可能的材料特性阵列。这项工作的成功完成将使结构粘合剂、3D原型、MEMS、牙科材料、光学材料和复合材料等过程中的应用受益。受这项研究影响的研究生的数量和多样性将通过与教育部目前指导的GAANN项目的互动而增加。本科生将通过自主学习项目和本科助学金的研究经验直接参与研究。

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.