Poly spiropyran

Photoresponsiveness of Poly(spiropyran-L-glutamate) under Acidic Conditions... 

Chung DJ, Ito Y, Imanishi Y (1994) Preparation of porous membranes grafted with poly (spiropyran-containing methacrylate) and photocontrol of permeability. J Appl Polym Sci 51 2027-2033... 

Higuchi, A. Hamamura, A. Shindo, Y Kitamura, H. Yoon, B. O. Mori, T. Uyama, T. Umezawa, A. Photon-modulated changes of cell attachments on poly(spiropyran-co-methyl methacrylate) membranes. Biomacromolecules 2004, 5, 1770-1774. 

Many examples are known such as the Fries rearrangement in aromatic polyesters or in some poly(methyl methacrylates) with poly(spiropyran) groups. 

Sunlight-induced Conformational Transitions in Spiropyran-containing Polypeptides 13.2.2.1 Spiropyran-modified Poly(L-glutamate)s... 

Poly(L-glutamate)s containing various molar percentages of spiropyran units in the side chains (XV) have been prepared by treating poly(L-glutamic acid) with N-(2-hy-droxyethyl) -spiropyran in the presence of dicyclohexylcarbodiimide and 4-pyrrolidino-pyridine.[60 62] The structure and photochromic behavior of the modified polymers are shown in Figure 8. 

Fig. 9 Absorption spectra of poly(L-glutamic acid) containing 85% spiropyran units, in HFP 1) sample kept in the dark ...

The structures of spiropyran-modified poly(L-glutamate)s are strongly affected by light or dark conditions, as demonstrated by the CD spectra in Figure 10. Before irradiation, the colored solutions show the CD spectrum of a random coil conformation. After exposure to sunlight, the colorless solutions display the typical CD pattern of the a-helix, thus indicating that the isomerization of the side chains causes a transition from coil to helix in the polypeptide chains. The photoinduced conforma-... 

Quite interesting photoresponsive behavior was observed when spiropyran-modified poly(L-glutamate) was dissolved in HFP and a small amount of trifluoroacetic acid... 

Fig. 11 Poly(L-glutamic acid) incorporating 85 mol% spiropyran units in the side chains. Effect of irradiation on CD spectra in various HFP/MeOH solvent mixtures in the presence...

Fig. 13 Reverse photochromic reactions of spiropyran-modified poly(L-lysine) (XVI) in hexafluoro-2-propanol.

Fig. IS Poly(L-lys ine) containing 46 mol% spiropyran units (XVI) in HFP/ NEt3. Variation of ellipticity at 222 nm as a function oftriethylamine concentration forthe sample kept in the dark (continuous line) and after irradiation (dashed line).

SchemelO Chemical structure ofthe polypeptide obtained after introducing spiropyran units into the side chains of succinylated poly(L-lysine) (XVII). 70 ...

Photomechanical effects have been also observed in monolayers obtained from poly(L-glutamic acid) modified with carbocyanine1831 and spiropyran dyes.184 In the latter case, irradiation at 254 nm produced changes in the molecular conformation, which in turn caused photomodulation of the surface pressure and surface area of the films. From all these examples, it appears that photoresponsive monolayers are quite fascinating systems, which may eventually come to be regarded as a machine to transform light into mechanical energy . 81 ... 

O. Pieroni, A. Fissi, F. Ciardelli, and D. Fabbri, Spiropyran-containing poly(L-glutamic acid). Photochromic and conformational behavior in acid conditions, Mol. Cryst. Liq. Cryst., 246, 191-194 (1994). 

The number of cycles in DHI 7 increases since oxygen is excluded, which, after activation to 102, causes destruction of the colored betaine 9.3 The number of Z cycles measured (e.g., in Saran) exceeds Z50 = 600. The Z50 equals the number of cycles leading to 50% of the original extinction of the colored form (Z 80 equals 80% of the original E). Similar matrix effects have been observed with spiropyrans.57 Typical values are given in Table 6.4. In a poly(vinyl butyral) (TrosifolR) matrix, the number of cycles for DHI 7 —> 9 exceeds Z50 = 50 00.3-7... 

When the most common spiropyran SP-4 was mixed in poly(y-benzylglutamate) to prepare a film, a reversible change in optical rotation was observed upon 365 nm light irradiation and visible light irradiation [49], The largest Aa before and after UV irradiation at sodium D-line (589 nm) was 1.225° for 4 mol% concentration. It was supposed that the change might have arisen from the chiral interaction between the chiral polypeptide environment and the colored merocyanine. Indeed, an induced CD was observed. 

Extensive studies on photochromic liquid-crystalline polymers have been made by Krongauz et al,2 Liquid-crystalline phases caused marked colour changes of poly(acrylates)98 and poly(siloxanes) substituted with spiropyran side chains upon UV irradiation owing to the aggregation of the photomerocyanines." In contrast, spirooxazines attached to liquid-crystalline polymer backbones displayed no aggregation and hence exhibited normal photochromism similar to that in solution. Fulgimides bound covalently to the side chains of nematic liquid-crystalline polymers also showed normal photochromism. 

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