Terthiophene-Containing Copolymers and Homopolymer Blends as High-Performance Dielectric Materials

This work explores the dielectric and polarization properties of block copolymers and homopolymer blends containing a terthiophene-rich, electronically polarized block (PTTEMA) and an insulating polystyrene block (PS). PTTEMA-b-PS block copolymers were synthesized by reverse addition-fragmentation chain transfer (RAFT) polymerization, and PTTEMA/PS homopolymer blends with the same PTTEMA weight percentages were produced by solution blending. DSC and XRD characterization show that crystallinity increases with PTTEMA content, indicating the presence of terthiophene-rich crystalline domains. Under an applied electric field, these domains are electronically polarized, but the insulating PS block inhibits current leakage, resulting in enhanced dielectric properties. Impedance measurements show that relative permittivity increases with PTTEMA content. The permittivity values are higher in PTTEMA-b-PS copolymers with moderate PTTEMA content due to the ability of the PS block to inhibit PTTEMA association, resulting in a higher density of isolated, terthiophene-rich polarizable domains. Freestanding PTTEMA/PS blend films containing up to 40 wt % PTTEMA have almost 40% greater recoverable energy density compared to pure PS films polarized to the same electric field strength.