Interaction of Polar and Nonpolar Polyfluorenes with Layers of Two-Dimensional Titanium Carbide (MXene): Intercalation and Pseudocapacitance

This article provides insight into the interaction of synthetic conjugated polymers [polyfluorene derivatives (PFDs)] with layers of two-dimensional titanium carbide (Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>). Three derivatives with nonpolar, polar, and charged nitrogen-containing functionalities were synthesized via the Suzuki polycondensation reaction. The organic–inorganic PFD/Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> hybrids were prepared and characterized using X-ray diffraction and a range of microscopic and spectroscopic techniques to elucidate the host–guest interaction mechanism. We show that polar polymers with charged nitrogen-containing ends have the strongest interaction with the Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> layers, yielding an increase in interlayer spacing and large shifts in spectroscopic peaks. Furthermore, the effect of polymer backbone juxtaposition between Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> layers on pseudocapacitance is discussed in detail. Our results suggest that new organic materials capable of intercalation between the layers of Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> and other MXenes may be used in the design of hybrid structures for high-performance energy storage applications and beyond.