Photoresponsive polymer surfaces

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...

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

Very varied applications have been proposed soil release properties of easy care cotton, assymetric solvents for the resolution of racemates and ligand exchange chromatography, " flame retardant properties, polymeric dyes which were reviewed by Marechal, chemical modification of surfaces, " chelating resins, photoresponsive polymers, " modification of polymers to alter or to remove unstable groups " and photoresists. " Chemical modification of telechelic oligomer end groups is of major importance to increase their reactivity and their selectivity. ... 

The copolymerizations were carried out in benzene solution (50 vol%), in the presence of diisopropyl peroxydicarbonate as the initiator, on the surface of glass or mercury. A representative condition is 100 mmol of ethylacrylate, 0.66 mmol of bis-photochrome dimethacrylate, and 0.096 mmol of diisopropyl peroxydicarbonate. Table 4 summarizes the photoresponsive polymers with spirobenzopyran chromophores. 

In the case of undoped PVCa films, impurities and surface states dominate the photoconduction mechanism (6) leading one to question any study of intrinsic pKotoconduction in organic polymers. Poly(N-vinylcarbazole) films yellow under ambient laboratory conditions. Work in our laboratory (7) has shown that ageing of a purified sample of PVCa leads to an increase in photoresponse in the 350-450 nm region while there is an initial drop in photoresponse in the 250-... 

The electron transfer from Ru(bpy)2+ to MV2+ is very rapid, the order being 10s—10 M-1 s . But the irradiation of an aqueous solution of both the compounds does not give a photoresponse at the electrode dipped in that solution, because the back electron transfer from MV+ to Ru(bpy)j+ is also very rapid thereby no photochemical products are accumulated in the photostationary state (Scheme 6), However, when Ru(bpy)2 + is modified on the electrode surface by utilizing polymer coating, the electrode shows photoresponse 95), Such a modification of the electrode makes it photoresponsive, to afford a new type of photodiode. 

The surface of a carbon electrode was at first coated with a thin film of an anionic polymer such as sodium poly(styrene-sulfonate) 95) or nafion 96) (thickness thousand A) then the cationic Ru(bpy)2+ was adsorbed in the anionic layer electrostatically. The modification was also made by coating water insoluble polymer pendant Ru(bpy)2 + ( ) from its DMF solution 97). These Ru(bpy) +/polymer modified electrode gave a photoresponse in the MV2+ solution with the Pt counter electrode 95-97) The time-current behaviours induced by irradiation and cutoff of the light under argon are shown in Fig. 28. It is interesting to see that the direction of the photocurrent reversed at the electrode potential of ca. 0.4 V (vs. Ag—AgCl) under... 

Dyes such as erythrosin B [172], eosin [173-177], rose bengal [178,179], rhodamines [180-185], cresyl violet [186-191], thionine [192], chlorophyll a and b [193-198], chlorophyllin [197,199], anthracene-9-carboxylate [200,201], perylene [202,203] 8-hydroxyquinoline [204], porphyrins [205], phthalocyanines [206,207], transition metal cyanides [208,209], Ru(bpy)32+ and its analogs [83,170,210-218], cyanines [169,219-226], squaraines [55,227-230], and phe-nylfluorone [231] which have high extinction coefficients in the visible, are often employed to extend the photoresponse of the semiconductor in photoelectro-chemical systems. Visible light sensitization of platinized Ti02 photocatalyst by surface-coated polymers derivatized with ruthenium tris(bipyridyl) complex has also been attempted [232,233]. Because the singlet excited state of these dyes is short lived it becomes essential to adsorb them on the semiconductor surface with... 

The morphological changes discussed in Section 15.4.1.2 were obtained for monolayers at assembled states in 2D. In such an assembled state, secondary effects such as generation of 3D collapse are accompanied on the solid surface. This should be ascribed to the limited allowance of lateral diffusion compared to the rate of the photoisomerization process. For observation of intrinsic photoresponse of the monolayer, separation of the polymer chain is highly desired, ideally on a single-chain level. 

In this chapter we describe conformationally photoresponsive CD-systems of various eomplexity by distinguishing them among functionalized CDs and CD-eontaining small complexes (2.1) supramoleeular nanoaggregates of CD-containing units (2.2) CD-containing polymer-like arrays (2.3) functional surfaces based on CD reeognition (2.4). 

FIGURE 5.5.3 Control of cell adhesion on photoresponsive surfaces, (a) Access control of GRGDS peptides for biospecific cell adhesion by photoinduced cis-trans Isomerization of terminal azobenzene residues in grafted polymers (54). 

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