Abstract : An experimental study of aging in glassy material, based on the
analogy between spin glasses and structural glasses, has been
realized introducing an effective temperature Teff of this
weakly out of equilibrium systems. This new observable is measured
with the fluctuation dissipation ratio.
The measurement of Teff on the dielectric properties of a
polymeric glass (polycarbonate) after a quench below the glass
temperature transition shows that the fluctuation dissipation
theorem is strongly violated. The amplitude and the persistence
time of this violation are decreasing functions of frequency. At
frequency larger than 1 Hz it persists for about 3 hours. The
origin of this violation is a highly intermittent dynamics
characterized by large fluctuations. This intermittency seems to
depend on the cooling rate and the stop temperature. This dynamics
seems to be in good agreement with a theoretical interpretation
based on the trap model.
Similar intermittent behaviour has been measured for a colloidal
glass (Laponite) during the sol-gel transition whereas no
violation and no intermittency have been observed after a slow
cooling rate quench realized on another polymeric glass,
poly(methyl) methacrylate (PMMA).
We present also a preliminary mechanical measurement of the
fluctuation dissipation relation on a polycarbonate rod via an
original two arms Nomarski interferometer.