This paper explores whether the photochromic reaction of a molecule embedded in a polymer film can affect its surface adhesion properties, as measured by shear strength and delamination in water. The adherence of polystyrene (PS) to glass was chosen as a model system. Two commercially available photochromes—a spiropyran derivative 1′,3′-dihydro-1′,3′,3′-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2′-(2H)-indole]) (SP) and a diarylethene derivative 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)-3,3,4,4,5,5-hexafluoro-1-cyclopentene (DAE)—are studied in detail. Both photochromic reactions can significantly enhance the adhesion of PS to a glass surface. The most dramatic results were obtained for PS/SP films, whose shear strength increased by a factor of 7 while the delamination rate was suppressed by at least 2 orders of magnitude after exposure to UV light. The enhanced polymer adhesion could only be partially reversed, even after extended exposure to visible light completely regenerated the UV-absorbing isomer. Nanoindentation and heating experiments suggest that the limited reversibility results from changes in polymer internal structure. We hypothesize that the adhesion changes arise from localized polymer and molecular motions that eliminate void spaces and surface gaps at the polymer–glass interface. The results show that adhesive forces between a prototypical polymer and an inorganic substrate can be modulated by photochromic reactions of embedded molecules.

中文翻译：

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非共价光致变色聚合物粘合

本文探讨了嵌入聚合物膜中的分子的光致变色反应是否会影响其表面粘附性能，如通过剪切强度和在水中的分层来衡量。选择聚苯乙烯（PS）对玻璃的附着力作为模型系统。两种市售的光致染料-螺吡喃衍生物1'，3'-二氢-1'，3'，3'-三甲基-6-硝基螺[2 H -1-苯并吡喃-2,2'-（2 H）-吲哚]）（SP）和二芳基乙烯衍生物1,2-双（2,4-二甲基-5-苯基-3-噻吩基）-3,3,4,4,5,5-六氟-1-环戊烯（DAE）-进行了详细研究。两种光致变色反应均可以显着增强PS对玻璃表面的附着力。对于PS / SP薄膜，获得了最引人注目的结果，其PS / SP薄膜的抗剪强度提高了7倍，而暴露于UV光后的脱层速度被抑制了至少2个数量级。即使长时间暴露于可见光下，增强的聚合物附着力也只能部分逆转，从而完全吸收了紫外线吸收异构体。纳米压痕和加热实验表明，有限的可逆性是由聚合物内部结构的变化引起的。我们假设粘附力的变化是由于局部的聚合物和分子运动引起的，这种运动消除了聚合物-玻璃界面上的空隙和表面间隙。结果表明，可以通过嵌入分子的光致变色反应来调节原型聚合物与无机底物之间的粘合力。