8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P7.94Thu 811:10-14:00Relaxation dynamics in PVAc ultrathin polymer filmsinvestigated at nanometer scaleDaniele Prevosto, 1 Massimiliano Labardi, 1 Nguyen Kim Hung, 1 Mauro Lucchesi, 1Simone Capaccioli, 1 and Pierangelo Rolla 21 IPCF-CNR, L. go B. Pontecorvo 3, 56127, Pisa, Italy2 Dip. Fisica, Univ. Pisa, Pisa, ItalyThe investigation of geometric confinement and interfacial effects on relaxation dynamics of ultrathinpolymer films has been subject of many investigations with sometimes apparently contrastingresults. The understanding of the correct length scale characterizing the observed differences ofrelaxation properties with respect to the bulk is still not satisfactory. The real physical mechanismbeneath the effects of interfacial interactions on polymer dynamics is still not understood. A trulylocal investigation technique can benefit the investigation, allowing to study the polymer dynamicsat the truly interface with nanometric spatial resolution. We recently applied an atomic forcemicroscope based technique [1], namely local dielectric spectroscopy, allowing to measure the dielectricrelaxation dynamics with spatial resolution of few tens of nanometers [2]. I will presentand discuss our recent results on ultrathin polumer films of pure poly(vinyl acetate) as well as ananocomposite of poly(vinyl acetate) and montmorillonite [2]. In the case of pure polymer filmsthe effect of molecular weight, moisture and interfacial interactions is considered. We observeda speed up of dynamics in samples prepared on gold substrate for thicknesses smaller than threetimes the gyration radius. The moisture was found to enhance such effect, paralleling the plasticizationeffect observed in the bulk. Regarding the films prepared with the nanocomposite weobserved for the first time a slowing down of dynamics in region in contact with the montmorilloniteplatellets [2]. The lenght scale over which this effect disappears is estimated to be smallerthan about 30-40 nm, which is the spatial resolution of the instrument.[1] P. S. Crider, N. E. Israeloff et al. Appl. Phys. Lett. 91, 013102 (2007).[2] M. Labardi, D. Prevosto et al. J. Vacuum Sc. Tech. B C4D11 (2010).94