Determining the Relation Between Molecular Structure and Macroscopic Heat Transport in Oriented and Stressed Polymers.

TECHNICAL SUMMARY:

An experimental study into the origins of anisotropic thermal conductivity of solid

polymers is proposed. In particular, a relationship between the molecular structure of

the polymer and the resulting macroscopic properties is sought. It has already been

established that (1) deformed, cross-linked elastomers exhibit an anisotropic thermal

conductivity tensor, k (2) the tensor k is linearly related to the extra stress tensor,

for the polymer in the same state, and (3) the constant of relation for these two

quantities exhibits a universal value of 0.03, independent of chemistry for the few

systems studied, when properly made dimensionless. In this work a set of experiments

has been designed that will distinguish between competing theories to describe these

observations. A non-invasive optical technique called Forced Rayleigh Light Scattering

to examine novel material states is used. Results will necessarily distinguish between

competing theories on the origins of the effect.

The results of the study will have broad impact on the transport modeling of advanced

materials containing plastic. While previous work showed how non-isothermal

modeling of liquids requires an additional complexity because of anisotropy, it also

suggested that this complexity could be easily modeled through use of a phenomenological

relation to stress. The current work, if successful, should determine if similar

principles apply to the solid polymer during cooling.

NON-TECHNICAL SUMMARY:

An experimental study into the origins of how heat flows differently in different

directions for solid polymers, such as plastic, is proposed. In particular, a relationship

between how the molecules are behaving and the resulting heat-flow properties

is sought. In this work a set of experiments has been designed that will distinguish

between competing theories to describe these observations using a non-invasive optical

technique called Forced Rayleigh Light Scattering. Results will necessarily distinguish

between competing theories on the origins of the effect.

The results of the study will have broad impact on the modeling of advanced materials

containing plastic. While previous work showed how temperature modeling of these

liquids requires an additional complexity, it also suggested that this complexity could

be easily modeled through use of a simple relation to stress which is typically calculated

already. The current work, if successful, should determine if similar principles

apply to the solid polymer during cooling.

Secondly, as part of the project, a display explaining the key optical technique employed

will be provided to the Holography Museum in Chicago. Visitors will learn that

holography is used to study material properties, and how the technique is employed.