We report the synthesis of oligothiophene-containing polymer brushes and their application as nanodielectric materials in capacitors. Specifically, terthiophene-containing methacrylate polymer brushes were synthesized via a "graft from" technique by a combination of ring-opening metathesis polymerization (ROMP) and reversible addition fragmentation chain transfer (RAFT) polymerization. Both X-ray scattering and thermal studies indicated that polymer brushes led to the formation of small nanoscale crystalline domains (similar to 2 nm) dispersed in an amorphous matrix. Notably, the film forming capability and processability are greatly improved in comparison with corresponding homopolymers. Transparent freestanding films could be readily fabricated based on these polymer brushes and used for dielectric property studies. The adoption of polymer brush architecture into the oligothiophene-containing polymers has been proved to be an effective strategy to improve the mechanical robustness of films. Published by Elsevier Ltd.