Orientational order of single-wall carbon nanotubes in stretch-aligned photoluminescent composite films

We study the alignment of single-wall carbon nanotubes in polyvinylalcohol composites using polarized Raman and photoluminescence spectroscopies. Nanotubes are well dispersed down to the individual scale in the composites as revealed by the strong photoluminescence signal. Alignment can be continuously adjusted by hot stretching the composites. We propose a simple relation to measure the order parameter based on the assumption that only one single component of the Raman polarizability tensor is nonzero. The similar profiles of spectra measured in different polarization configurations validate this assumption. The orientation of the nanotubes under uniaxial stretching is well modelized by a simple affine model assuming deformation at constant volume.