Spatially resolved heat conduction in polar perhydrotriphenylene inclusion compounds studied by means of thermal waves

Scanning pyroelectric microscopy was applied to study the local thermal diffusivity in polar perhydrotriphenylene (PHTP) inclusion compounds. A thermal wave technique with special heat flow and pyroelectric detection principles was used to measure the longitudinal (K-parallel to) and transversal (K-perpendicular to) thermal diffusivity of needle shaped crystals. As expected, we have found a higher thermal conductivity along the channel direction: K-parallel to> K-perpendicular to. K-parallel to also showed a variation along the needle axis, the K-parallel to values near the capping faces being higher than in the center region. Based on these observations we suggest a relation between the longitudinal thermal conductivity and the local density of orientational defects of the dipolar guest molecules which reaches a maximum in the area around the seed. These findings are in agreement with previous pyroelectric studies, revealing a macrodomain structure and a spatially dependent pyroelectric activity for two different PHTP inclusion compounds. (C) 2000 American Institute of Physics. [S0021-8979(00)05416-5].status: publishe