Enhanced Dielectric Properties of a Poly(dimethyl siloxane) Bimodal Network Percolative Composite with MXene

Excellent comprehensive dielectric properties (including dielectric constant and loss) are essential for electromechanical transducers. This work introduced a bimodal network composite with poly(dimethyl siloxane) (PDMS) and delaminated Ti3C2Tx sheets (d-Ti3C2Tx) modified with hyperbranched polysiloxane (HPSi) (referred to as HPSi-d-Ti3C2Tx). Before the final cross-linking, HPSi-d-Ti3C2Tx, trapped with short-chain PDMS (CS-PDMS) and long-chain PDMS (CL-PDMS), was pre-reacted, which formed a distinct bimodal network structure. d-Ti3C2Tx/PDMS and HPSi-d-Ti3C2Tx/PDMS composites with different filler loadings were prepared, and their percolation thresholds (fc) were 1.32 and 1.43 vol %, respectively The dielectric constant of 1.40 vol % HPSi-d-Ti3C2Tx/PDMS is 23.7 at 102 Hz, which is 1.5 times that of 1.28 vol % d-Ti3C2Tx/PDMS and 8.5 times that of pure PDMS. Meanwhile, the dielectric loss of HPSi-d-Ti3C2Tx/PDMS composite is still relatively small (0.11 at 103 Hz). The origin of dielectric property optimization of the composite is attributed to the boundary capacitor model, the accumulated charges at the interfaces between the conductive filler and the insulating polymer matrix of the composite, and the distinct bimodal network structure.