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Equilibrium and out-of-equilibrium dynamics in a molecular layer of azopolymer floating on water studied by Interfacial Shear Rheology
- Source :
-
Journal of Non-Crystalline Solids . Jan2011, Vol. 357 Issue 2, p580-586. 7p. - Publication Year :
- 2011
-
Abstract
- Abstract: We report the details of the construction and calibration of a sensitive surface rheometer, inspired by an instrument described in the literature, adapted to the study of photosensitive polymeric materials. By high resolution video tracking of the motion of a floating magnetized needle we are able to measure the viscoelastic complex shear modulus G of a Langmuir monolayer with an accuracy of 5*10−6 N/m. This instrument is then employed for the rheological characterization of a Langmuir monolayer of a photosensitive azobenzene polymer, which can be brought out of equilibrium by a suitable photoperturbation. The shear modulus is measured as a function of temperature, illumination power and wavelength. The reversible rheological changes induced in the film by photo-perturbation are monitored during time, observing a transition from a predominantly elastic (G mainly real) to a viscoelastic regime (real and imaginary parts of G comparable). These results are confirmed by a comparison with independent measurements performed using other rheological techniques. Finally a discussion is made, taking into account the results of a recent X-ray photon correlation spectroscopy (XPCS) experiment on the same polymer in equilibrium and out of equilibrium. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00223093
- Volume :
- 357
- Issue :
- 2
- Database :
- Academic Search Index
- Journal :
- Journal of Non-Crystalline Solids
- Publication Type :
- Academic Journal
- Accession number :
- 57511796
- Full Text :
- https://doi.org/10.1016/j.jnoncrysol.2010.06.057