Photoresponsive polymers

Masahiro Irie received his B.S. and M.S. degrees from Kyoto University and his Ph.D. in radiation chemistry from Osaka University. He joined Hokkaido University as a research associate in 1968 and started his research on photochemistry. In 1973 he moved to Osaka University and developed various types of photoresponsive polymers. In 1988 he was appointed Professor at Kyushu University. In the middle of the 1980 s he invented a new class of photochromic molecules - diaryl-ethenes - which undergo thermally irreversible and fatigue resistant photochromic reactions. He is currently interested in developing singlecrystalline photochromism of the diarylethene derivatives. 

Photoresponsive polymers can be prepared by coupling photochromic compounds which undergo structural changes upon irradiation with light and subse-... 

Note 1 Examples of the changes in photosensitive polymers are a change in molecular shape (photoresponsive polymer), a change in its constitution (photoreactive polymer), and a reversible change in color (photochromic polymer). 

Novel Methodology for Immobilization of Biomolecules on the Surface of a Photoresponsible Polymer Containing Azobenzene Moiety... 

The editors hope that these volumes will provide the reader with an overview of various aspects of photoresponsive polymers. We recommend that readers also examine other volumes in this series to learn more about related topics. In addition the editors thank the authors of the chapters in these volumes and the staff of Springer for their contribution to these volumes and accept responsibility for any errors or inaccuracies. 

Polymer-based photochromic systems have been studied extensively and are attractive in terms of practical applications because of their advantages of stability and processability. A number of reviews and articles dealing with various aspects of photochromic polymers and photoactive biomaterials have been published. 68 Chiral photochromic peptides are discussed in Chapter 13, and photochromic liquid crystals and polymers for holographic data storage and nonlinear optics have been reviewed. 69 Specific stereochemical effects in chiral photoresponsive polymers include ... 

Photoresponsive polymers are quite special polymers, able to respond to light and dark conditions and thus giving rise to reversible variations in their structure and conformation. These photoinduced structural changes may in turn be accompanied by reversible changes in the physical and chemical properties of the polymeric materials. 

Photoresponsive polymers can be obtained by introducing photochromic units, such as azobenzene or spiropyran groups, into the macromolecules of polymeric compounds. As described in Chapter 1 of this book, photochromic compounds can exist in two different states, such as two isomeric structures that can be inter-converted by means of a light stimulus, and the relative concentrations of which depend on the wavelength of the incident light. For instance, in azobenzene compounds, photochromism is due to trans-cis photoisomerization around the N=N double bond, while in spiropyran compounds photochromism involves interconversion between the neutral spiro form and the zwitterionic merocyanine form (Figure 1). 

Thus far, photoresponsive polymers have been intensively investigated and significant advances have been made on fundamental aspects and strategies. However, it is fair to say that they have found only limited practical application. 

Fig. 3 Photoresponsive polymer surface sensitive to pH and light. Adsorption and release of cytochrome c triggered by pH (b, c, and d) release of the polymer layer and cytochrome c by breaking the host-guest interactions between surface-tethered azo dye and cyclodextrin via light irradiation (a and d). The molecular structure on the right represents the host-guest complexa-tion of the azo dye with the cyclodextrin-modified poly(acrylic acid). Reprinted, with permission, from [68]. Copyright (2009) Wiley Interscience...

More recently, Sugiura et al.11 developed a fully functional microvalve based on this photoresponsive behavior, which was composed of poly(/V-isopropylacrylamide) functionalized with the chromophore spirobenzopyran (pSPNIPAAm). The microvalve was fabricated in a polydimethylsiloxane (PDMS) microchannel by in situ photopolymerization. Blue light irradiation (18 to 30 s) to the gel induced photoisomerization of the spirobenzopyran chromophore which resulted in shrinkage due to dehydration of the gel, thus causing the microvalves to open, as seen in Figure 23.7. In this example, localized irradiation enabled independent control of three photoresponsive polymer gel microvalves, which had been fabricated on a single microchip. 

V. CHIRALITY OR HELICITY INDUCTION ON ACHIRAL PHOTORESPONSIVE POLYMER FILMS BY CIRCULAR POLARIZED LIGHT... 

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