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

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TECHNICAL SUMMARY:An experimental study into the origins of anisotropic thermal conductivity of solidpolymers is proposed. In particular, a relationship between the molecular structure ofthe polymer and the resulting macroscopic properties is sought. It has already beenestablished that (1) deformed, cross-linked elastomers exhibit an anisotropic thermalconductivity 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 twoquantities exhibits a universal value of 0.03, independent of chemistry for the fewsystems studied, when properly made dimensionless. In this work a set of experimentshas been designed that will distinguish between competing theories to describe theseobservations. A non-invasive optical technique called Forced Rayleigh Light Scatteringto examine novel material states is used. Results will necessarily distinguish betweencompeting theories on the origins of the effect.The results of the study will have broad impact on the transport modeling of advancedmaterials containing plastic. While previous work showed how non-isothermalmodeling of liquids requires an additional complexity because of anisotropy, it alsosuggested that this complexity could be easily modeled through use of a phenomenologicalrelation to stress. The current work, if successful, should determine if similarprinciples apply to the solid polymer during cooling.NON-TECHNICAL SUMMARY:An experimental study into the origins of how heat flows differently in differentdirections for solid polymers, such as plastic, is proposed. In particular, a relationshipbetween how the molecules are behaving and the resulting heat-flow propertiesis sought. In this work a set of experiments has been designed that will distinguishbetween competing theories to describe these observations using a non-invasive opticaltechnique called Forced Rayleigh Light Scattering. Results will necessarily distinguishbetween competing theories on the origins of the effect.The results of the study will have broad impact on the modeling of advanced materialscontaining plastic. While previous work showed how temperature modeling of theseliquids requires an additional complexity, it also suggested that this complexity couldbe easily modeled through use of a simple relation to stress which is typically calculatedalready. The current work, if successful, should determine if similar principlesapply to the solid polymer during cooling.Secondly, as part of the project, a display explaining the key optical technique employedwill be provided to the Holography Museum in Chicago. Visitors will learn thatholography is used to study material properties, and how the technique is employed.