Research Institute for Sustainable Chemistry , National Institute of Advanced Industrial Science and Technology (AIST Chugoku) , 3-11-32 Kagamiyama , Higashihiroshima , Hiroshima 739-0024 , Japan.
Research Institute for Sustainable Chemistry , National Institute of Advanced Industrial Science and Technology (AIST) , Tsukuba Central 5, 1-1-1 Higashi , Tsukuba , Ibaraki 305-8565 , Japan.
ACS Appl Mater Interfaces. 2018 Sep 26;10(38):32649-32658. doi: 10.1021/acsami.8b09319. Epub 2018 Sep 13.
Photocurable adhesives based on polymers and resins are an integral part of different production processes because of their fast curing and local area bonding ability. Recently, dismantlable adhesives have attracted a lot of attention for recycling adherends or replacement of adhesion defects. However, adhesives that allow repeatable bonding and debonding solely by light irradiation, i.e., without heat activation, are lacking. Here, ABA-type triblock copolymers consisting of poly(meth)acrylates bearing an azobenzene moiety (A block) and 2-ethylhexyl (B block) side chains were synthesized and utilized as photocurable adhesives. In contrast to the azo homopolymers, the block copolymer structure and incorporation of the soft middle block actualized a low concentration of the azobenzene moiety and consequently, higher flexibility of the resultant copolymers. This enabled film formation of the azobenzene-based adhesives and light-induced bonding for the first time. On the basis of the photoisomerization of the azobenzene moiety, changes in their viscoelastic property, i.e., softening and hardening, were induced by UV irradiation at 365 nm (50-100 mW cm) and green light irradiation at 520 nm (40 mW cm), respectively. In fact, two glass substrates were bonded with the self-standing polymer film, which was sequentially softened and hardened upon UV and green light irradiations. They exhibited shear strengths of 1.5-2.0 MPa, and UV irradiation lowered the adhesion strength to 0.5-0.1 MPa. Interestingly, the repeatable bonding and debonding abilities of the polymers were accomplished without loss of the adhesion strength.
基于聚合物和树脂的光固化胶粘剂由于其快速固化和局部粘结能力，是不同生产工艺的重要组成部分。最近，可拆解胶粘剂因其可回收粘结体或替代粘结缺陷而受到广泛关注。然而，缺乏仅通过光照射（即无需热激活）即可实现重复粘结和脱粘的胶粘剂。在这里，我们合成了由带有偶氮苯部分（A 嵌段）和 2-乙基己基（B 嵌段）侧链的聚（甲基）丙烯酸酯组成的 ABA 型嵌段共聚物，并将其用作光固化胶粘剂。与偶氮均聚物相比，嵌段共聚物结构和软中间嵌段的掺入实现了偶氮苯部分的低浓度，从而使所得共聚物具有更高的柔韧性。这使得基于偶氮苯的胶粘剂能够进行薄膜形成和光诱导粘结。基于偶氮苯部分的光异构化，其粘弹性能（即软化和硬化）在 365nm（50-100mWcm）的 UV 照射和 520nm（40mWcm）的绿光照射下分别发生变化。事实上，两个玻璃基板用自支撑聚合物膜粘结，该聚合物膜在 UV 和绿光照射下依次软化和硬化。它们的剪切强度为 1.5-2.0MPa，UV 照射将粘结强度降低至 0.5-0.1MPa。有趣的是，聚合物的重复粘结和解粘能力是在不损失粘结强度的情况下实现的。
