Photomechanics of light-activated polymers
Photomechanics of light-activated polymers
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DOI：
10.1016/j.jmps.2009.03.003
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发表时间：
2009-07-01
影响因子：
5.3
通讯作者：
Dunn, Martin L.
中科院分区：
文献类型：
--
作者：
Long, Kevin N.;Scott, Timothy F.;Dunn, Martin L.
光激活聚合物是一类令人兴奋的现代材料，当受到特定波长的光照射时，它们会做出机械反应。虽然将光激发与机械行为联系起来的机制的细节是复杂的，并且因材料的不同而不同，但它们之间有足够的共性，从而允许开发一个通用的建模框架来描述光力学。光激活聚合物的共同特征包括光与材料的相互作用，这引发了光化学反应，从而改变了交联聚合物网络结构。许多这样的结构变化导致聚合物网络的演化，以及随后的宏观变形。当这一过程被适当地执行时，它可以实现光机械形状记忆效果。在本文中，我们开发了一个三维有限变形建模框架来描述光激活聚合物体系的光机械响应。这一框架集成了四种有助于宏观光力学行为的耦合现象：光物理、光化学、化学-机械耦合和机械变形。化学机械耦合包括化学诱导的交联网络的结构改变，从而导致随后的变形。我们通过将交联网络分解成由原始网络和光化学改变的网络组成的两个部分来描述这一行为；两者都在光机械变形过程中演变。本文提出的建模框架具有足够的通用性，适用于在这四个领域中的每一个领域都具有不同机理的光激活聚合物体系。使用这种建模方法，我们建立了两个新近发展的光激活聚合物体系的本构模型[Lendlein，A.，Hong yan，J.，Junger，O.，Langer，R.，2005。光诱导形状记忆聚合物。《自然》434(7035)879；斯科特，T.F.，施奈德，A.D.，库克，W.D.，鲍曼，C.N.，2005。交联型聚合物的光致塑性。科学308(5728)1615]。对于Scott和他的同事开发的材料，我们通过测量和数值模拟光致应力松弛和弯曲变形来验证我们的模型，得到了很好的测量结果和预测结果。最后，我们利用该模型研究了光力学参数(外加应变大小、照射时间和强度、光吸收剂浓度)和网络演化规律对材料响应的影响。(C)2009爱思唯尔有限公司。保留所有权利。
Light-activated polymers are an exciting class of modern materials that respond mechanically when irradiated by light at particular wavelengths. While details of the mechanisms that connect the optical excitation to mechanical behavior are complex and differ from material to material, there is sufficient commonality among them to permit the development of a generalized modeling framework to describe the photomechanics. The features shared by light-activated polymers involve light interacting with the material, which triggers photochemical reactions that alter the structure of the crosslinked polymer network. Many such structural alterations result in an evolution of the polymer network, and subsequent macroscopic deformation. When this process is appropriately executed it can enable a photomechanical shape-memory effect. In this paper, we develop a three-dimensional finite-deformation modeling framework to describe the photomechanical response of light-activated polymer systems. This framework integrates four coupled phenomena that contribute to macroscopic photomechanical behavior: photophysics, photochemistry, chemomechanical coupling, and mechanical deformation. The chemomechanical coupling consists of chemically induced structural alterations of the crosslinked network that result in subsequent deformation. We describe this behavior through a decomposition of the crosslinked network into two components consisting of an original network and a photochemically altered network; both evolve during photomechanical deformation. The modeling framework presented in this paper is sufficiently general that it is applicable to light-activated polymer systems that operate with various mechanisms in each of the four areas. Using this modeling approach, we develop constitutive models for two recently developed light-activated polymer systems [Lendlein, A., Hongyan, J., Junger, O., Langer, R., 2005. Light-induced shape-memory, polymers. Nature 434 (7035) 879; Scott, T.F., Schneider, A.D., Cook, W.D., Bowman, C.N., 2005. Photoinduced plasticity in crosslinked polymers. Science 308 (5728) 1615]. For the material developed by Scott and his co-workers we validate our model by measuring and numerically simulating photoinduced stress relaxation and bending deformation and obtain good agreement between measurements and predictions. Finally, we use the model to study the effects of photomechanical parameters (applied strain magnitude, irradiation time and intensity, and photoabsorber concentration) and the behavior of the network evolution rule on the material response. (C) 2009 Elsevier Ltd. All rights reserved.