Direct evidence for effect of molecular orientation on thermoelectric performance of organic polymer materials by infrared dichroism

A direct evidence by infrared dichroism is reported for the first time for the effect of molecular orientation on thermoelectric (TE) performance of organic polymer materials. The preferred orientation was induced by mechanical uni-axial stretching of the films of neat polyaniline (PANI) and its nanocomposites with reduced graphene oxide (rGO) or multi-walled carbon nanotube (MWCNT). Five characteristic bands of Fourier transform infrared (FTIR) spectra were chosen, and quantitative investigations were carried out using the dichroic ratios measured by polarized FTIR spectra. The influences of draw ratio and content of inorganic carbon nanoparticles were taken into account. The results show that the TE performance (including anisotropic TE function) can be conveniently tuned by polymer molecular orientation induced by mechanical stretching, which shed light on the understanding of molecular mechanism towards structure-TE performance relationship, and will speed up the applications of organic polymer TE materials.