Poly , spirobenzopyran groups

Fig. 7. Viscosities of poly(methyl methacrylate) having spirobenzopyran groups (13 mol%) at 30 °C (A) in benzene ( ) in the dark (O) under irradiation (A > 310 nm) (B) in dichloroethane [21]...

Fig. 13. Photomechanical behavior of poly(ethyl acrylate) cross-linkal with spirobenzopyran groups [33]- Influence of temperature and stress time in min...

We can use the change of dipole moment as a driving force of conformational change of the polymer chain by incorporating the chromophores into the pendant groups. A representative example is poly(methyl methacrylate) with pendant spirobenzopyran groups. ... 

Poly(methacrylic acid) with pendant spirobenzopyran groups also showed photostimulated conformational changes in methanol.Visible light irradiation of the solution increased the viscosity while ultraviolet light irradiation caused a decrease in the solution viscosity. 

In the poly(ethyl acrylate)rubbers described above spirobenzopyran and aromatic azo chromophores were incorporated in the cross-links between the polyacrylic chains. In contrast, Matejika and al. studied cross-linked systems with azo side groups they considered especially the relative importance of the thermal effects occurring during photomechanical conversion. Most interesting are their results on copolymers ccmtaining low concentrations of chromophore (for which heat effects are less important), namely copolymers of )8-hydroxyethyl methacrylate (0.99) and azonaphthol methacrylate (XII) (0.01) swollen in water... 

It should be expected that the influence of the chain segment mobility is most pronounced when the photochrome groups are inserted into a semirigid polymer backbone instead of being attached as mobile side groups in copolymers. Therefore, polyesters have been prepared by condensation of bis-hydroxymethyl-spirobenzopyrans with bisacid dichlorides.followed by polyesterification with bisphenol-A43,46). Thus, a photo-chromic poly(bisphenol-A-pimelate) (polyester XI) of the following formula was obtained. 

Poly(methacrylic acid) with spirobenzopyran pendant groups is soluble in polar solvents, such as methanol or water, when the content of spirobenzopyran is less than 20 mol%. A methanol solution of the polymer has a weak red color under thermal equilibrium conditions, which indicates the presence of merocyanine form in equilibrium with spiropyran form. Visible irradiation completely bleached the absorption (merocyanine - spiropyran) after the light was removed, the absorption gradually reappeared in the dark (spiropyran merocyanine). Ultraviolet irradiation caused enhancement of the absorption near 530 nm (merocyanine merocyanine) the intense absorption again returned to the thermal equilibrium intensity after removal of the light (merocyanine - spiropyran). Together with these isomerizations. 

Figure 23 Changes in the viscosity of a methanol solution of poly(methacrylic acid) with spirobenzopyran pendant groups (Structure (12), x = 0.926) on visible light (Xi > 470 nm) irradiation and UV light (410 nm > 2 > 310 nm) irradiation at 20°C. Concentration of the polymer is 0.25 g dL . ...

Photoinduced mechanical response of a monolayer consisting of poly(methyl methacrylate) with spirobenzopyran pendant groups was examined at an air-water interface [55]. Irradiation with UV light pulses isomerized the spiropyran chromophore and led to a relative surface pressure increase of up to 10%. The pressure decreased progressively in the dark, and a typical decay time was estimated as being approximately 20 min. The decay can be accelerated by use of visible light pulses (Fig. 26). The whole process can be repeated several times. 

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