Light-scattering study of a supercooled epoxy resin

Area of Science:

• Materials Science
• Condensed Matter Physics
• Physical Chemistry

Background:

• Fragile glass-forming liquids exhibit complex dynamics near the glass transition.
• Understanding relaxation processes is crucial for predicting material properties.
• Diglycidyl ether of bisphenol-A serves as a model system for studying these dynamics.

Purpose of the Study:

• To investigate the dynamics of diglycidyl ether of bisphenol-A using light scattering and photon correlation spectroscopy.
• To characterize the structural (alpha-) relaxation process.
• To compare experimental relaxation times with viscosity data and test theoretical models.

Main Methods:

• Depolarized Rayleigh-Brillouin light-scattering.
• Photon correlation spectroscopy.
• Measurements conducted over a wide temperature (261-473 K) and frequency (1 Hz-300 GHz) range.

Main Results:

• The structural (alpha-) relaxation process was identified.
• No secondary relaxation was observed, contrasting with previous dielectric spectroscopy findings.
• A fractional power law (tau proportional to eta^0.89) was found for light-scattering relaxation times, deviating from the Stokes-Einstein-Debye model.
• Cooperative motion and a characteristic length scale were inferred from the deviation.

Conclusions:

• The study reveals distinct dynamics probed by light scattering compared to dielectric methods.
• The observed deviation from the Stokes-Einstein-Debye model supports theories of cooperative motion in supercooled liquids.
• The findings provide insights into the fluctuation theory of glass transition.