Mass transport in low Tg azo-polymers: Effect on the surface relief grating induction and stability of additional side chain groups able to generate physical interactions

International audienceThe nanostructuration ability of low glass transition temperature (Tg) azo-polysiloxanes films is investigated at working temperatures close or higher than the film Tg. The behavior of materials incorporating additional side chain nitrobenzene or naphthalene groups and as a result presenting different Tg is compared in terms of the surface modulation dynamics and stability of the induced topographic modifications.This comparison is carried out under light exposure and in dark environment. We demonstrate the ability to optically generate surface modulations on these materials even at operating temperatures corresponding to the film Tg. Along with a modification of the opto-mechanic properties correlated with the materials chemical structure, a collapse of the surface structures occurring with different dynamics in materials of similar Tg is highlighted. These observations suggest the existence of an additional mechanism rather than a purely thermal redistribution of the polymer chains in the films

Azobenzene based polymers as photoactive supports and micellar structures for applications in biology

International audienceAzo-polymers have been investigated for the large structural modifications occurring under light excitation. Photo induced isomerizations of the azobenzene molecular units can provide cooperative forces able to affect self-assembling processes in the liquid state or leading to an efficient mass transport in the solid state, which results in large deformations of film surfaces. We introduce here our studies on azopolymers based on a polysiloxane matrix bearing specific chemical functions, whose composition can be finely tuned for applications in the biological field. Depending on their chemical structure, these materials are able to form photoactive surfaces with adjustable topographic properties or photosensitive micellar architectures in aqueous solvents. In the first case, the ability to control the surface shape at the optical wavelength scale aims to provide photoactive cell growth supports with tuneable properties, for the investigation of the environment influence on cell development. The optical properties of the materials are presented, as well as the preliminary studies showing the materials potential to modify the cell response to the surface. The stability of the films surface in contact with biological media and the implications on the cell behavior are also addressed. The second property involving formation of micellar structures is demonstrated by showing the ability of the materials to encapsulate and provide controlled release of small molecules pointing to their potential use in drug delivery applications