Dismantlable Adhesion Interface Featuring a Thermo/Photocleavable Molecular Layer

Abstract

Adhesion technology, in which materials are bonded together to create an integrated material, is widely used in a range of household, commercial, and industrial applications. [1] In recent years, adhesives have received more attention from the viewpoint of energy consumption. In the automobile industry, reducing vehicle mass is a key factor regarding the demand for improving energy efficiency. Therefore, adhesives are becoming more important and more in demand owing to their availability to bond different materials that cannot be bonded through typical mechanical methods. [2] Among these demands for new adhesion technologies, sustainability through material lifecycle has also been recognized as an important factor. [3] Dismantlable adhesives that have been developed to meet these requirements exhibit sufficient adhesion strength during use and can be easily separated by external stimuli when the material in question needs to be recycled or repaired. [4][5][6] Various types of dismantlable adhesives have been developed that reduce the adhesive force by utilizing stimuli such as heating, [7][8][9][10][11][12] light irradiation, [13][14][15][16][17][18][19][20][21] electric fields, [22] magnetic fields, [23] and chemical treatments. [24][25][26] These dismantlable adhesives maintain the changed state caused by applying the stimulus; thus, there is no regain in their original adhesive strength even in the absence of the stimulation. This feature enables easy separation without the need for continuous stimulation. Despite the recent progress on these functional adhesives, neither is currently universally accepted in dismantling systems. [6] One considerable reason of this circumstance is that the dismantling mechanisms are limited to changes in bulk state, such as controlling the cohesiveness of the adhesives. This limitation requires large amounts of trigger materials, such as stimulusresponsive molecules, to dismantle these adhesives by changing their entire state. Therefore, the development to achieve both sufficient adhesion strength and an efficient dismantling system is difficult because the overall condition of adhesives needs to be involved.The surface treatment of adherends also plays a critical role in ensuring sufficient adhesion strength; altering the surface treatment is more efficient than changes in bulk state. [27] A typical example of surface treatment is a coating process applied to the base materials, which is known as a primer treatment. This has been conventionally used as a method to improve adhesion strength. [28] For example, phosphoric acid primers are used to improve adhesion between resin cements and zirconia ceramics, for which it is normally difficult to achieve suitable adhesion. [29,30] Organosilane compounds are used as coating agents to improve the adhesion strength between metal and

Photo-and Heat-Induced Dismantlable Adhesion Interfaces Prepared by Layer-by-Layer Deposition

“…28 The average peel strength of the test specimen of the APS/Di9AC/APS layer was determined to be 10 N/10 mm, which is almost the same as that observed in our previous report. 28 The dismantling properties of the APS/Di9AC/APS layer were evaluated by applying a stimulus to the specimen. The conditions of the applied stimuli were determined based on the cleavage characteristics of the anthracene dimer: irradiation with 280 nm light for 1 min or heating at 180 °C for 1 min.…”

Photoswitchable Adhesives of Spiropyran Polymers

“…Meanwhile, as represented by marine plastic pollution, global environmental problems are worsening, and material recycling is strongly required. − In this context, switching of adhesives between strong bonding during use and on-demand debonding by external stimuli is a key technology to achieve both development of complex architectures and material recycling. , In particular, light is an ideal stimulus that can minimize effects on adherends due to the high spatiotemporal resolution and easy, precise control of the intensity and wavelength . To date, photoswitchable adhesives have been developed by utilizing a variety of photoresponsive systems including large structural changes of azobenzenes, − conjugation changes of diarylethenes, , dimerization of anthracenes, − photothermal effects of supramolecular motifs and dyes, − and other reactions. − Reversibly switchable polymer adhesives are particularly attractive because of their strong adhesion and recyclability. Similarly, large polarity changes in the photoisomerization between noncharged spiropyran (SP) and zwitterionic merocyanine (MC) seem highly suitable for photocontrol of adhesion (Figure a) , because molecular polarity and related interactions between adhesives and substrate surfaces are dominant factors to generate adhesion force. − The dipole moment (μ) drastically changes between 4–6 D for SP and 14–18 D for MC. , However, to the best of our knowledge, SP has been only used as additives in polymer adhesives ,, or as low-molecular-weight adhesives .…”

Adhesive Interfaces toward a Zero-Waste Industry

“…A dismantlable adhesive based on a thermo- and photocleavable layer containing an anthracene photodimer has been demonstrated . Anthracene has been widely characterized before and is known to form reversible covalent bonds through photodimerization and photocleavage processes.…”

“…134 A dismantlable adhesive based on a thermo-and photocleavable layer containing an anthracene photodimer has been demonstrated. 135 Anthracene has been widely characterized before and is known to form reversible covalent bonds through photodimerization and photocleavage processes. This switchable anthracene layer was formed in the adhesive interface and increased the adhesion strength due to the formation of covalent bonds between the substrate and the adhesive.…”