Pressure-tunable thermal conductivity observed for bisamide functionalized diacetylene crystals

The polymerization of monomeric diacetylene (DA) crystals exhibits a strong dependence on the intermolecular distance relative to the van der Waals distance, which can be tuned with macroscopic mechanical stimuli. In this study, we report the effect of external pressure on the heat transport characteristics of bisamide functionalized DA (BA-DA) crystals. The thermal conductivity (kappa) of BA-DA crystals in the monomeric state could be enhanced with pressure from 0.42 +/- 0.13 W m(-1) K-1(<= 30 MPa) to 1.10 +/- 0.50 W m(-1) K-1(>= 50 MPa) but was not significantly affected by the structural change after photopolymerization. Raman and Fourier-transform infrared spectroscopy revealed that the kappa of the BA-DA crystals is correlated with the IR-active vibrational modes of N-H and C=O bonds correlated with the intermolecular hydrogen bonding. The UV polymerization significantly affected the Raman-active vibrational modes of monomers (-C C-C C-), but their effect on the kappa was negligible, which is likely attributed to the anharmonic interatomic potential. These results can potentially be utilized in polymer-based material design for thermal management technologies, such as printing heat circuits in an economically viable way or realizing a thermal barrier coating based on DA monomers.

Automated summary

External pressure can significantly enhance the thermal conductivity of bisamide functionalized diacetylene crystals, which is correlated with the vibrational modes related to intermolecular hydrogen bonding. UV polymerization affects Raman-active vibrational modes of monomers but has negligible effect on thermal conductivity. These findings may have applications in designing polymer-based materials for thermal management technologies.