Poly azobenzene

Monolayers representing two-dimensional arrays of membrane-mimetic assemblies, consisting of azobenzene (poly-L-lysine) with 43 % loading of the photoisomerizable units, were prepared.1441 The compressed trans-azobenzene polymer mono-layer exhibited a surface pressure of 7 mN m 1, whereas photoisomerization of the monolayer to the cis-azobenzene state by UV light decreased the surface pressure to... 

Host-guest Polyallylamine [P-cyclodextrine], poly (acrylic acid) [azobenzene], poly(methacryUc acid) [azobenzene] Poly(L-aspartic acid) [adamantine] Dextran [carboxymethyl-, a-cyclodextrin, p-cyclodextrin]... 

Synthesis of Poly(p-phenylene) Containing Azobenzene Unit 60so... 

R. Yuan, Y.Q. Chai, and R.Q. Yu, Poly(vinyl chloride) matrix membrane pH electrode based on 4,4 -bis[(N,N-diakylamino)-methyl]azobenzene with a wide linear pH response range. Analyst 117, 1891-1893 (1991). 

Fig.7. Quadratic Stark effect spectrum of a poly(methylmetacrylate) film doped with an azobenzene-linked amphiphile C180AZ0C00H (solid line). Dotted line, broken line, and dash and dotted line show an absorption spectrum of the film, its first derivative, and second derivative, respectively.

Figure 7 shows the quadratic Stark spectrum of a poly(methyl metacrylate) film doped with a azobenzene-linked amphiphile, 4-octadecyloxy-4 -nitroazobenzene. Using eq. (5) and the most characteristic spectral point on the AT/T curves, where dD/dX = 0 and d2D/dXa = 0, the value of Ap was evaluated to be 5.4 debye. Further, the p value of the azobenzene-linked amphiphile was calculated to be 24 x 10 30 esu at a fundamental wavelength of 1064 nm. The p values of azobenzene-linked amphiphiles employed in this study were evaluated by the procedure mentioned here. The values are listed in Table 2 in the section 1.1.1. 

McGrath and Junge [36] reported a photoresponsive poly(aryl ether) dendrimer with azobenzene as the dendrimer core. These dendrimers exhibited reversible trans to cis photoisomerization by irradiation at 350 nm. The authors proposed the use of this type of dendrimer as novel photoswitchable transport vectors. This is based on the expected ability of dendrimers to encapsulate or eject small molecules reversibly upon light perturbation. 

Figure 16.5 Reversible switching of amphiphilic azobenzene modified poly(propylene imine) dendrimer on quartz, and at the air-water interface (inset) [74]...

Figure 16.7 TEM picture (uranyl acetate staining) of vesicles reported by Schenning etal. [44] (A) schematic representation of the bilayer, (B) palmitoyl-and (C) azobenzene-modified poly(propylene imine) dendrimers used in the construction of the aggregates...

Tsuda K, Dol GC, Gensch T, Hofkens J, Latterini L, Weener JW, MeijerEW, De SchryverEC. Fluorescence from azobenzene functionalized poly(propylene imine) dendrimers in self-assembled supramolecular structures. J Am Chem Soc 2000 122 3445-3452. 

Unlike W and Mo catalysts, Rh catalysts are not suited to oriho-swhstxtutcd phenylacetylenes because Rh catalysts are rather sensitive to the steric effect. Instead, Rh catalysts are suitable to various phenylacetylenes having polar groups (e.g., ether, ester, amine, carbazole, imine, nitrile, azobenzene, nitro groups) at ra-position, resulting in the formation of high MW poly(phenylacetylenes). Many such examples are found in Table 3. 

Cast multibilayers prepared from an azobenzene-containing surfactant (33) [426] and from mixtures of 33 and 5 display only short-term stabilities and low solubilities in water. These disadvantages have been overcome by coating the multibilayers with cellulose acetate and by using poly(vinyl alcohol) as a binder [429], The method of choice in preparing these composite cast multibilayers... 

Scheme 3 Chemical structure of poly(L-glutamic acid) modified with 4-amino-azobenzene (III), and 4-amino-azobenzene-4 -sul-fonic acid sodium salt (IV).

Fig. 5 Poly(L-glutamic acid) containing 56 mol% azobenzene units in the side chains (III). CD spectra in trimethylphosphate before (continuous line) and after (dashed line) irradiation at 360 nm. Below 250 nm, molar ellipticity is based on the mean residue weight above 250 nm, the ellipticity is referred to one azo-Glu residue.

The conformational behavior can be quite different in aqueous solution. Below pH 5, a sample of poly(L-glutamic acid) containing about 30 mol% azobenzene units adopts a P-structure that is not affected by light. Above pH 7, the polypeptide is random coil and the conformation is, once more, not affected by the photoisomerization of the azo side chains. However, at pH values in the range 5-7 (close to the pK of the conformational transition), irradiation causes a remarkable diminishing of the ordered structure, which is completely reversed in the dark.120,221... 

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