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

P8.8Thu 811:10-14:00Metastable highly ordered supercooled liquid phaseinherited from molecular beam grown glassesSimona Capponi, 1 Simone Napolitano, 1 and Michael Wubbenhorst 11 Katholieke Universiteit, Celestijnenlaan, 200 D 3000, Leuven, BelgiumThe nature of the glass transition still remains one of the most intriguing phenomena in softmatter science. Recently, theoretical models ascribe vitrification to the presence of structuredregions which, diverging upon cooling, prevent crystallization. [1, 2] Here we report a dielectricinvestigation of ultrathin films of polyols, hinting to an experimental evidence of such structures.Those layers were grown in the glassy state by molecular beam deposition [3] and monitoredafter annealing above the glass transition temperature. They exhibit longer relaxation times withrespect to the bulk values, and an enhancement in the dielectric strength up to a factor 4.5. Asthis quantity is affected by dipole-dipole correlation, these findings indicate a remarkably higherorientational order in our systems, which we attribute to an improved organization of the MRCOregions, locally favored structures predicted by the two order parameters model, and characterizedby medium range orientational order. Consequently, MRCOs present higher thermal stability, andthey affect the dynamics of the system up to temperatures well above T g , where the liquid remainsin a metastable, highly ordered, phase. Our scenario is supported by agreement with numericalsimulations. [4] Isothermal measurements revealed an extraordinary kinetic stability, as shown bya conversion time into the normal state exceeding the structural relaxation time by nine decades.The results will be discussed in terms of changes in the H bonding networks induced by physicalvapor deposition below T g . The role of confinement will also be examined.[1] V. Lubchenko, P. G. Wolynes, Annu. Rev. Phys. Chem. 58 235-266, 2007.[2] H. Tanaka, J. non-Cryst. Solids 351 3772-3772, 2005.[3] S. F. Swallen et al. , Science 315 353-356, 2007.[4] H. Tanaka, et al. , Nat. Mater. 9 324-331.8