Holographic Grating Relaxation and Photon Correlation Spectroscopic Studies of Viscoelastic Liquids Above the Glass Transition (Preprint)
Abstract
Photon correlation spectroscopic (PCS) and holographic grating relaxation (HGR) techniques are used to measure the dynamics of density fluctuations in liquid orthoterphenyl, salol and poly(propylene glycol) oligomers in both the normal and supercooled liquid regimes down to their glass transition temperatures. In the PCS study a strongly temperature dependent nonhydrodynamic mode due to structural relaxation is observed in each of the above mentioned glass forming liquid. The shape of the nonhydrodynamic mode is nonexponential and can be fit to a stretch exponential function for each liquid. The nonhydrodynamic mode measured in PCS is shown to be the dynamic longitudinal compliance of the liquid. The tracer diffusion coefficients of camphorquinone in the above glass forming liquids do not obey the Stokes-Einstein equation. The slowness of the structural relaxation of the host liquid and the finite size of the tracer are identified to be the cause for the departure from the Stokes Einstein equation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1992
- Accession Number
- ADA252485
Entities
People
- C. H. Wang
- Shou-Shu Gong
Organizations
- University of Nebraska-Lincoln Department of Chemistry