https://doi.org/10.1140/epje/i2015-15056-9
Regular Article
Experimental evidence of ultrathin polymer film stratification by AFM force spectroscopy
1
Institut des Molécules et Matériaux du Mans (IMMM) - UMR CNRS 6283, Université du Maine, Avenue Olivier Messiaen, 72000, Le Mans, France
2
Laboratoire d’Ingénierie des Matériaux de Bretagne (LIMATB), Université de Bretagne Sud, Rue Saint Maudé, 56321, Lorient, France
3
Institut Charles Sadron (ICS), Université de Strasbourg, 67034, Strasbourg, France
* e-mail: nicolas.delorme@univ-lemans.fr
Received:
3
February
2015
Revised:
25
March
2015
Accepted:
11
May
2015
Published online:
22
June
2015
By performing Atomic Force Microscopy measurements of pull-off force as a function of the temperature, we were able to probe the dynamic of supported thin polystyrene (PS) films. Thermal transitions induce modifications in the surface energy, roughness and surface modulus that are clearly detected by AFM and related to PS chain relaxation mechanisms. We demonstrated the existence of three transition temperatures that can be associated to the relaxation of polymer chains located at different depth regions within the polymer film. Independently of the film thickness, we have confirmed the presence of a region of high mobility for the polymer chains at the free interface. The thickness of this region is estimated to be above 7nm. The detection of a transition only present for film thicker than the gyration radius Rg is linked to the dynamics of polymer chains in a bulk conformation (i.e. not in contact with the free interface). We claim here that our results demonstrate, in agreement with other techniques, the stratification of thin polymer film depth profile in terms of relaxation behavior.
Key words: Soft Matter: Polymers and Polyelectrolytes
© EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg, 2015