Polymer Chain Conformation in CNT/Polystyrene Nanocomposites by SANS

Polymer conformations are a critical factor that affects the performance of polymer nanocomposites. Using small angle neutron scattering, we probed chain conformations and confinement of polymers in both SWCNT/polystyrene ($R_{SWCNT}$ \textless\ $R_{g})$ and MWCNT/polystyrene ($R_{MWCNT}$ $\sim$ $R_{g})$ nanocomposites. Through contrast matching experiments, we optimize the dPS:hPS ratio (0.725:0.275) to minimize the scattering from CNTs. To fit the scattering data, we developed a fitting model that includes scattering from polymer chains, rod networks, and defects. We found that the rod network scattering increases as the CNT concentration increases (0.3wt{\%} - 10wt{\%}) in both SWCNT and MWCNT composites, and the rod network scattering is much higher for SWCNT due to the smaller mesh size. When the CNTs concentration is below 2wt{\%}, there is no significant change in $R_{g}$ for both SWCNT and MWCNT nanocomposites. Above 2wt{\%}, the $R_{g}$ for SWCNT nanocomposites increases monotonically as a function of CNT concentration ($\sim$ 30{\%} increase for 10wt{\%} SWCNT loading), while the $R_{g}$ for MWCNT is not affected.