Topochemical Reaction Induces Anisotropy, Decreasing Solid-State Thermal Conductivity.

Area of Science:

• Materials Science
• Polymer Chemistry
• Organic Electronics

Background:

• Dynamic thermal conductivity in organic materials is crucial for applications like thermal switches.
• Understanding the relationship between molecular structure, processing, and thermal transport is essential for designing such materials.

Purpose of the Study:

• To investigate the effect of photoinduced polymerization on the thermal conductivity of [2,2 '-bi-1H-indene]-1,1 '-dione-3,3 '-diheptylcarboxylate (BIT).
• To explore the potential of polyBIT as a solid-state organic thermal switch.

Main Methods:

• Photoinduced polymerization of BIT to polyBIT.
• Measurement of thermal conductivity on polycrystalline thin-films.
• Experimental determination of heat capacity.
• Theoretical calculations to understand thermal transport mechanisms.

Main Results:

• A greater than 4-fold decrease in through-plane thermal conductivity was observed after polymerization.
• The decrease in thermal conductivity is partly attributed to induced anisotropy in the polymer.
• Reduced heat capacity supports the observed decrease in thermal conductivity.
• Morphology changes, phase transitions, and thermal degradation influence the thermal depolymerization reaction.

Conclusions:

• Photoinduced polymerization of BIT into polyBIT significantly reduces thermal conductivity.
• Induced anisotropy plays a key role in the observed thermal transport behavior.
• Designing solid-state organic thermal switches requires consideration of molecular structure, processing, and material properties like heat capacity and degradation.