Characterization of Dynamic Heterogeneity

Xiangfu Shi
Qin Qian

Mechanical Hole Burning Spectroscopy (MSHB): Evidence for Heterogeneous Dynamics in Polymer Systems

Xiangfu Shi

To understand the origins of the non-exponential relaxation of polymeric systems in the terminal relaxation regime, we have developed a unique mechanical spectroscopic hole burning (MSHB) technique to study the ideas of spatial and dynamic heterogeneity. Clear mechanical holes are burned far above the glass temperature and in the terminal regimes for a LDPE melt and for a PS solution in diethyl phthalate. The results suggest that MSHB is a potentially powerful tool to examine dynamics of complex fluids and that polymer dynamics reflect a spatial heterogeneity that is not readily captured in ordinary continuum models.

Funding

• Petroleum Research Fund
• National Science Foundation
• Texas Higher Education coordinating Board

 

Nano-confinement Effects on Dynamic Heterogeneity using Rubber Network as Soft Confinement Templates

Qin Qian

The effect of nanoconfinement on dynamic heterogeneity are being examined in the context of an NSF funded Nanotechnology Interdisciplinary Research Team (NIRT). Here we are looking at rubber networks as a means of providing a "soft" confinement template for these studies. In order to characterize the size scales relevant to the heterogeneity we are making measurements of the melting point depression of small molecule liquids in the rubber. Subsequently, We will investigate the effects of the rubber crosslink density on the observed melting point depression and in the future, will investigate the dynamics of glass forming liquids confined in the well characterized rubber network templates.

Funding

• National Science foundation