Reversible Photo‐Mechanical Switching Behavior of Azobenzene‐Containing Semi‐Interpenetrating Network under UV and Visible Light Irradiation

Abstract

Summary: Light‐induced reversible changes in elasticity of semi‐interpenetrating network (semi‐IPN) films bearing azobenzene moieties were achieved under both ultraviolet (UV) and visible light irradiation. The semi‐IPN film was prepared by a cationic copolymerization of azobenzene‐containing vinyl ethers in a linear polycarbonate (PC) film as a matrix. When the irradiation was switched on and off, the semi‐IPN film showed rapid reversible deformation with the same behavior occurring over a range of wavelengths, including both the UV and visible regions. The observed reversible deformation of the film was attributed to the decrease in the film's elasticity, which was assumed to be caused by the frequent trans‐cis cycling isomerization of azobenzene moieties taking place during the UV and visible light irradiation. This cycling makes it difficult for the azobenzene groups to aggregate, thus hindering their ability to function as pseudo‐crosslinking points. magnified image

Anisotropic Photomechanical Response of Stretched Blend Film Made of Polycaprolactone‐Polyvinyl Ether with Azobenzene Group as Side Chain

“…However, this postulated mechanism [20,21] does not fully explain the anisotropic photomechanical responses of the stretched films. A newly introduced factor in the stretched films is the uniaxial stretching, which makes the crystalline PCL orient to the direction of stretching via rearrangement.…”

“…This means that the film reversibly deformed in response to the switching on and off of the light without any delay as previously reported in the system of Azo-PVE/PC. [19][20][21] In Figure 3a, changes in temperature of the film during the repeating process of irradiation are also illustrated. When the light was turned on and off, the temperature of the film gradually increased and recovered at a rate of 1 8C Á min À1 .…”

“…A similar photomechanical response behavior to the switching on and off of the irradiation with Azo-PVE/PCL film was exhibited. In Table 1 the discussion in the previous report, [21] this high deformation value of Azo-ME/PCL must be induced by the softening effect of the model compound Azo-ME, which has a lower molecular weight than Azo-PVE. Figures 5 and 6 show the photomechanical responses of stretched Azo-PVE/PCL and Azo-ME/PCL films when stretched by 300%, and in Figure 7, the anisotropic responses are illustrated schematically.…”

“…[18] Any such light-induced change, especially a rapid and reversible photoresponse, is also a highly desirable property of materials because, there are potential applications to smart photoresponsive devices and this promise of highly functional devices is being explored with great interest. The rapid and reversible photoresponses [19][20][21] have been reported by Kim et al using polymer blend films consisting of poly(vinyl ether) with azobenzene moiety as a side chain and polycarbonate as a matrix. The blend films A rapid and reversible anisotropic photomechanical response of polymer film was achieved by using uniaxially stretched blend film composed of polycaprolactone and poly(vinyl ether) with azobenzene moiety (Azo-PVE) as a side chain.…”

The Study of Thermal Effect Suppression and Wavelength Dependence of Azobenzene-coated FBG for UV Sensing Application

“…최근 이러한 단점들을 극복한 UV 에 민감한 아조벤젠 (azobenzene) 폴리머가 코팅된 광섬유 격자 센서가 제안되었다 [8] . [4][5][6][7] . [8] , 스트레인과 중심파장의 관계 는 간단히 다음 수식으로 표현된다.…”