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 Ti₃C₂T sheets (d-Ti₃C₂T) modified with hyperbranched polysiloxane (HPSi) (referred to as HPSi-d-Ti₃C₂T). Before the final cross-linking, HPSi-d-Ti₃C₂T, trapped with short-chain PDMS (C_S-PDMS) and long-chain PDMS (C_L-PDMS), was pre-reacted, which formed a distinct bimodal network structure. d-Ti₃C₂T/PDMS and HPSi-d-Ti₃C₂T/PDMS composites with different filler loadings were prepared, and their percolation thresholds (f_c) were 1.32 and 1.43 vol %, respectively The dielectric constant of 1.40 vol % HPSi-d-Ti₃C₂T/PDMS is 23.7 at 10² Hz, which is 1.5 times that of 1.28 vol % d-Ti₃C₂T/PDMS and 8.5 times that of pure PDMS. Meanwhile, the dielectric loss of HPSi-d-Ti₃C₂T/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.