Photo-CuAAC Induced Wrinkle Formation in a Thiol-Acrylate Elastomer via Sequential Click Reactions
Photo-CuAAC Induced Wrinkle Formation in a Thiol-Acrylate Elastomer via Sequential Click Reactions
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DOI：
10.1021/cm502237b
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发表时间：
2014-09-23
影响因子：
8.6
通讯作者：
Bowman, Christopher N.
中科院分区：
文献类型：
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作者：
Alzahrani, Abeer A.;Nair, Devatha P.;Bowman, Christopher N.
两个顺序的点击反应在一个简单的方法中实现，用于在弹性体表面上产生定义良好的时空控制和持久的皱纹。利用click - thol - michael加成反应形成具有残余活性炔位点的交联聚合物，这些活性炔位点在整个网络中保持系留。潜伏的未反应的炔位点随后通过光诱导Cu(I)催化的炔叠氮环加成（CuAAC）反应与二叠氮单体反应，以增加交联密度。交联的增加使丙烯酸硫酯反应后的模量和玻璃化转变温度从1.6 MPa和2℃提高到4.4 MPa和22℃。然而，由于Cu（II）离子扩散到丙烯酸硫酯弹性体中的限制，CuAAC反应的第二阶段光聚合在空间上受到明显限制，从而在整个初始网络的深度上产生所需的交联梯度，并导致高度交联的皮层的形成。对于总薄膜厚度为1280 μ m的聚合物，这种方法可以在材料表面形成明确的、持久的、可重复的皱纹，其波长和振幅分别为8.50 +/- 1.60和1.41 μ m。通过使用扫描电子显微镜（SEM）和原子力显微镜（AFM）研究表面轮廓，进一步证明了使用树脂膜厚度控制这些皱纹的波长和幅度。此外，这种新技术允许皱纹形成的空间选择性，皱纹区域仅比光掩膜区域宽8 μ m。这种策略代表了一种独特的方法，可以在弹性体的整个表面上一步产生光导起皱。
Two sequential click reactions are implemented in a facile methodology used to generate well-defined spatiotemporally controlled and persistent wrinkles on the surface of an elastomer. The click thiol-Michael addition reaction was utilized to form a cross-linked polymer with residual, reactive alkyne sites that remained tethered throughout the network The latent, unreacted alkyne sites are subsequently reacted with diazide monomers via a photoinduced Cu(I)-catalyzed alkyne azide cycloaddition (CuAAC) reaction to increase the cross-link density. Increased cross-linking raised the modulus and glass transition temperature from 1.6 MPa and 2 degrees C after the thiol acrylate reaction to 4.4 MPa and 22 degrees C after the CuAAC reaction. However, the second-stage photopolymerization of the CuAAC reaction is significantly spatially restricted via limited Cu(II) ion diffusion into the thiol acrylate elastomer, thereby creating the desired cross-linking gradient throughout the depth of the initial network and leading to the formation of a highly cross-linked skin layer. This approach leads to the formation of well-defined, persistent, reproducible wrinkles on the surface of the material with wavelength and amplitude of 8.50 +/- 1.60 and 1.41 mu m, respectively, for a polymer with a 1280 mu m total film thickness. Control over the wavelength and amplitude of these wrinkles using the resin film thickness is further demonstrated by studying the surface profiles using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Additionally, this novel technique allows the spatial selectivity of wrinkle formation with a wrinkled area that is only 8 mu m wider than the photomasked area. This strategy represents a unique approach to generate photodirected wrinkling on the entire surface of the elastomer in one single step.