Photoresponsive New Polysiloxanes with 4‐Substituted Azobenzene Side‐Groups. Synthesis, Characterization and Kinetics of the Reversible Trans‐Cis‐Trans Isomerization

Hurduc, Nicolae; Adès, D.; Belleney, Joël; Siove, Alain; Sauvet, G.

doi:10.1002/macp.200700326

Cited by 15 publications

(16 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…They are respectively straight and bent in conformation (Fig. 8), and are photo-reversible under alternative irradiation of UV and visible light irradiation (Ercole et al 2010;Hurduc et al 2007). Therefore, they would show varied hydrophobic association in response to their conformations.…”

Section: Phase Transition Characterized By Turbidimetric Measurementmentioning

confidence: 97%

Thermal inverse phase transition of azobenzene hydroxypropylcellulose in aqueous solutions

Zhang

Liu

2016

Cellulose

View full text Add to dashboard Cite

Water soluble 2-azobenzenoxy-ethoxyhydroxpropylcelluloses (azo-EHPC) were synthesized by etherification reaction of bromoethoxy-azobenzene (BEA) with hydroxypropylcellulose (HPC) to study their phase transition behavior in aq. solution. The degree of substitution (DS) of the water soluble azoEHPCs was less than 0.066. Their chemical structure and thermal property were characterized by proton nuclear magnetic resonance ( 1 H-NMR), fourier transform infrared spectroscopy (FT-IR), and differential scanning calorimetry. The azo-EHPC showed a reversible sol-gel transition behavior in its aq. solution, i.e. a clear azo-EHPC aq. solution became turbid when the solution temperature surpassed a lower critical solution temperature (LCST). The sol-gel transition phenomenon was investigated by optical microscopy and turbidimetric measurement. It was found that the LCST was related to the cis-/transconformation of the azobenzene side group, the type of cyclodextrin (CD), concentration of azo-EHPC, and NaCl concentration. The LCST of azo-EHPC was lower than that of HPC (36.6°C) by at most 13.6°C, and the LCST of trans-azo-EHPC was less than that of cis-azo-EHPC by ca. 3°C. Additionally, the presence of CD in solutions displayed a positive effect on the LCST, i.e. increasing the LCST by 3-5°C. And this impact was more profound on the azo-EHPC with higher DS values. The thermoreversible phase transition mechanism was discussed. We proposed that the effect of DS, conformation of azobenzene group, azo-EHPC concentration, salt concentration, and CD on the LCST of azo-EHPCs was a rearrangement of the hydrophilic/hydrophobic interaction between side azobenzene groups and water molecules.

show abstract

Section: Phase Transition Characterized By Turbidimetric Measurementmentioning

confidence: 97%

Thermal inverse phase transition of azobenzene hydroxypropylcellulose in aqueous solutions

Zhang

Liu

2016

Cellulose

View full text Add to dashboard Cite

show abstract

“…The photo-excitation time used is large enough to obtain the maximum conversion of the trans isomer into the cis, according to previous studies of the photochromic behavior of the azo-polysiloxanes. 29 Molecular Modeling Simulations. The dipole moment values corresponding to the unsubstitued and para-substituted azophenols were calculated using the soft Materials Studio 4.0 (VAMP module, AM1 method).…”

Section: Methodsmentioning

confidence: 99%

“…28,29 Film Processing, Irradiation and Photochromic Evolution. The azo-polysiloxane films were spin-coated either onto a glass plate from chloroform solutions for surface free energy determination (3 wt% chloroform solution; 1,500 rpm; thickness around 1 µm), or onto quartz cell by casting 0.5 wt% chloroform, for the photochromic studies (film thickness around 500-600 nm).…”

Section: Methodsmentioning

confidence: 99%

“…Details concerning the spectrophotometric studies of the photoisomerization and thermal relaxation as well, of the p-CF 3 , p-CN, p-NO 2 -substituted and non-substituted azophenoxy-polysiloxanes, have been described previously. 29 It can be remind that photoisomerization kinetics were studied by following the evolution of the UV absorption of the trans isomers. Indeed, the UV-Visible spectra exhibit a strong absorption at around 350 nm characteristic of the π-π* transition of the trans isomers (ε trans ≈20,000-23,000 L mol -1 cm -1 ) and a weak absorption near 440 nm due to the n-π* transition of both isomers (ε trans ≈400-500 L mol -1 cm -1 ; ε cis ≈1,200-1,500 L mol -1 cm -1 ).…”

Section: Methodsmentioning

confidence: 99%

“…These results are not in keeping with the kinetics of cis-trans backisomerization followed by optical spectroscopy of films. 29 Indeed, the rate constants of the considered isomerization were found to be largely dependent on the electron-withdrawing ability of the substituent, the rate constants of relaxation increasing in the order: H < CF 3 < CN < NO 2 . 29 This apparent discrepancy can be attributed to the polymer matrix effect associated to the silicon polymer backbone motion, not detectable by spectrophotometry but leading to modification of the wettability of the surface measurable by the contact angle technique.…”

Section: Contact Angle Measurements and Surface Propertiesmentioning

confidence: 98%

See 2 more Smart Citations

Surface properties, thermal behavior, and molecular simulations of azo-polysiloxanes under light stimuli. Insight into the relaxation

Resmeriță

Epure

Hurduc³

et al. 2010

Macromol. Res.

Self Cite

View full text Add to dashboard Cite

Light-sensitive materials as azo-polymers have interesting applications in microelectronics, biology, or energy storage, due to their capacity to change their supramolecular ordering. Light-induced modifications result in i) changes in the azobenzene-groups dipole moment due to the trans-cis isomerization, ii) thermal backward cistrans relaxation, and iii) re-ordering of the polymer chain conformation. Conjugation of these phenomena leads to mass transport in the solid state, which is still not well understood. Changes in the surface properties of non-substituted and p-CF 3 ,-CN,-NO 2 -substituted azophenoxy-polysiloxane films, before and after photo-excitation, were examined. Molecular simulations were performed to evaluate the dipole-moments of the trans and cis p-substituted azobenzene groups and provide a general vision of the spatial arrangement of polymer chains. The role of trans-cis back relaxation and that of the polymer matrix relaxation on the surface and bulk of the materials was discussed. Surface free energy determination of the non-substituted azophenoxy-polysiloxane suggested that the relaxation process is dominated by the thermal slow back-isomerization of the cis fraction and not by the motion of a glassy polymer matrix involving both the surface and bulk. A less clear situation was presented by the semi-crystalline polysiloxanes with electron-withdrawing groups substituted in the para-position. This was attributed mainly to the similar values of the dipole-moment of trans and cis azo-group, the former being slightly more dipolar than the latter.

show abstract

Thermoresponsive surface prepared by atom transfer radical polymerization directly from poly(vinylidene fluoride) for control of cell adhesion and detachment

Dai

et al. 2009

J of Applied Polymer Sci

View full text Add to dashboard Cite

Thermoresponsive surface was prepared from commercial poly(vinylidene fluoride) (PVDF) films via surface-initiated atom transfer radical polymerization. The direct initiation of the secondary fluorinated site of PVDF facilitated grafting of the N-isopropylacrylamide (NIPAAm) monomer. The PVDF surfaces grafted with poly(N-isopropylacrylamide) [P(NIPAAm)] were characterized by X-ray photoelectron spectroscopy. Kinetics study revealed that the P(NIPAAm) chain growth from the PVDF surface was consistent with a ''controlled'' process. The temperature-dependent swelling behavior of the surfaces in aqueous solution was studied by atomic force microscope. At 37 C [above the lower critical solution temperature (LCST, about 32 C) of NIPAAm], the seeded cells adhered and spread on the NIPAAm grafted PVDF surface. Below the LCST, the cells detached from the P(NIPAAm)-grafted PVDF surface spontaneously. The thermoresponsive surfaces are potentially useful as stimuli-responsive adhesion modifiers in the biomedical fields.

show abstract

Photoresponsive New Polysiloxanes with 4‐Substituted Azobenzene Side‐Groups. Synthesis, Characterization and Kinetics of the Reversible Trans‐Cis‐Trans Isomerization

Cited by 15 publications

References 28 publications

Thermal inverse phase transition of azobenzene hydroxypropylcellulose in aqueous solutions

Thermal inverse phase transition of azobenzene hydroxypropylcellulose in aqueous solutions

Surface properties, thermal behavior, and molecular simulations of azo-polysiloxanes under light stimuli. Insight into the relaxation

Thermoresponsive surface prepared by atom transfer radical polymerization directly from poly(vinylidene fluoride) for control of cell adhesion and detachment

Contact Info

Product

Resources

About