Photochromic photomechanical effects

Some fine review articles dealing with various aspects of photochromic polymers are reported in the literature,11-91 and several photoresponse effects have been described. These include light-induced conformational changes, photostimulated variations of viscosity and solubility, photocontrol of membrane functions, and photomechanical effects. Here we provide an overview of the photoresponse effects... 

In this chapter we will consider to which extent conformational changes of the chromophores and connected chain segments of a photochromic polymer may induce changes of dimension of bulk polymers and thus generate reversible photomechanical effects. 

Menzel, H. Langmuir-Blodgett films of photochromic polyglutamates. 7. The photomechanical effect in monolayers of polyglutamates with azobenzene moieties in the side chains. Macromol. Chem. Phys., 195, 3747 (1994). 

Smets, G., Braeken, J. and Irie, M. (1978) Photomechanical effects in photochromic systems. Pure Appl. Chem., 50, 845—856. 

Matejka, L., Ilavsk,y M., Dusek, K. and Wichterle, O. (1981) Photomechanical effects in crosslinked photochromic polymers. Polymer, 22, 1511-1515. 

Matejka et al. synthesized several types of photochromic polymers based on a copolymer of maleic anhydride and styrene with azobenzene moieties both in the side chains and cross-links of the polymer network (Matejka et al., 1981 Matejka and Dusek, 1981 Matejka et al., 1979). The photomechanical effect was enhanced by an increase in the content of photochromic groups, and the photoinduced contraction of the sample amounted to 1% for a polymer with 5.4mol% azobenzene moieties. 

Some selected examples of 1,2-diarylethenes were shown in this review. Miyasaka and Irie et al. revealed the three-photon cyclization and two-photon cycloreversion of diarylethens (223) by a near-infrared femtosecond laser pulse at 1.28 pm. They also found single-molecule fluorescence photoswitching of a diarylethene-perylenebisimide dyad (225)." " Photomechanical effects of two-component cocrystal (226) composed of 1,2-diarylethene derivative and perfluoronaphthalene or hydrogen-bonded diarylethene-imidazoline crystalline (227) were examined. A variety of photochromic reactions of 1,2-diarylethenes in crystalline states were reported by Iiie et al. ... 

Matejka L, Dusek K, liavsky M. 1979. The thermal effect in the photomechanical conversion of a photochromic polymer. Polym Bull 1 659 664. 

There are two postulated mechanisms for photomechanical response, which taken together can explain the photochromic effect seen in this work. The first by Lovrien, " suggest that if a polymer interacts with some photochromic chromophore, it may undergo a conformational change when irradiated because the interactions between the polymer and the chromophore suffer changes. The second one, postulated by Matejka" and Irie, suggest that... 

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