Anisotropic Polymer Conformations in Aligned SWCNT/PS Nanocomposites

In our previous study of isotropic SWCNT/polystyrene (PS) nanocomposites, we found that the polymer radius of gyration (Rg) increases and the SWCNT mesh size decreases with increasing SWCNT concentration. Here, we investigate the effect of aligning SWCNTs on Rg and the SWNCT mesh. SWCNT alignment was accomplished by melt fiber spinning or extrusion, and small angle neutron scattering was used to probe the structure. As expected, SWCNT alignment produces anisotropic meshes. Below 2 wt{\%} SWCNT, no significant change in Rg is observed and Rg parallel and perpendicular to the direction of SWCNT alignment are comparable. More interestingly, at higher wt{\%} SWCNT the polymer conformations are anisotropic with a larger Rg perpendicular to the SWCNT than along the SWCNT. For example, with 6 wt{\%} SWCNT, the Rg perpendicular to the SWCNT is $\sim$ 15{\%} larger than parallel to the SWNCT. This anisotropy in the polymer conformation becomes more prominent at higher SWCNT concentrations, perhaps because at higher SWCNT concentrations the distribution of mesh shifts to smaller meshes (\textless 2Rg) so that a single polymer chain interacts with multiple SWCNTs. Implications of this finding will be discussed.