Grady Martha E, Birrenkott Cassandra M, May Preston A, White Scott R, Moore Jeffrey S, Sottos Nancy R
Department of Mechanical Engineering, University of Kentucky, 506 Administration Drive, Lexington, Kentucky 40506, United States.
Department of Mechanical Engineering, South Dakota School of Mines and Technology, 501 East Saint Joseph Street, Rapid City, South Dakota 57701, United States.
Langmuir. 2020 Jun 2;36(21):5847-5854. doi: 10.1021/acs.langmuir.0c00568. Epub 2020 May 17.
Functionalization of planar and curved glass surfaces with spiropyran (SP) molecules and localized UV-induced activation of the mechanophore are demonstrated. Fluorescence spectra of UV-irradiated SP-functionalized surfaces reveal that increases in surface roughness or curvature produce more efficient conversion of the mechanophore to the open merocyanine (MC) form. Further, force-induced activation of the mechanophore is achieved at curved glass-polymer interfaces and not planar interfaces. Minimal fluorescence signal from UV-irradiated SP-functionalized planar glass surfaces precluded mechanical activation testing. Curved glass-polymer interfaces are prepared by SP functionalization of E-glass fibers, which are subsequently embedded in a poly(methyl methacrylate) (PMMA) matrix. Mechanical activation is induced through shear loading by a single fiber microbond testing protocol. detection of SP activation at the interface is monitored by fluorescence spectroscopy. The fluorescence increase during interfacial testing suggests that attachment of the interfacial SP molecule to both fiber surface and polymer matrix is present and able to achieve significant activation of SP at the fiber-polymer matrix interface. Unlike previous studies for bulk polymers, SP activation is detected at relatively low levels of applied shear stress. By linking SP at the glass-polymer interface and transferring load directly to that interface, a more efficient mechanism for eliciting the SP response is achieved.
本文展示了用螺吡喃（SP）分子对平面和曲面玻璃表面进行功能化，以及对机械发色团进行局部紫外线诱导激活的过程。紫外线照射的SP功能化表面的荧光光谱表明，表面粗糙度或曲率的增加会使机械发色团更有效地转化为开放部花菁（MC）形式。此外，在弯曲的玻璃-聚合物界面而非平面界面上实现了力诱导的机械发色团激活。紫外线照射的SP功能化平面玻璃表面的荧光信号极小，无法进行机械激活测试。通过对E玻璃纤维进行SP功能化制备弯曲的玻璃-聚合物界面，随后将其嵌入聚甲基丙烯酸甲酯（PMMA）基质中。通过单纤维微粘结测试协议的剪切加载来诱导机械激活。通过荧光光谱监测界面处SP激活的检测。界面测试期间荧光的增加表明界面SP分子同时附着在纤维表面和聚合物基质上，并且能够在纤维-聚合物基质界面实现SP的显著激活。与之前对本体聚合物的研究不同，在相对较低的外加剪切应力水平下检测到了SP激活。通过在玻璃-聚合物界面连接SP并将载荷直接传递到该界面，实现了引发SP响应的更有效机制。
