Turning Plastics into Metals: Molecular and Ionic Alchemy in Crystalline Polymers

Plastics are generally regarded as electrical insulators because their electrons are localized within molecular orbitals. This view changed with the discovery of conjugated polymers, whose delocalized pi-electrons enable charge transport and semiconducting behavior. Despite decades of research, however, charge transport in conjugated polymers remains poorly understood because flexible, quasi-one-dimensional polymer chains cannot be fully described by conventional band theory.
Our research addresses this challenge by developing highly crystalline conjugated polymers with precisely controlled molecular packing. Their ordered structures enable coherent charge transport, while the periodic nanoscale free volume between neighboring chains provides pathways for ions and molecules. These channels allow reversible insertion and extraction of ions, enabling precise electrochemical control of carrier density without disrupting the crystal framework. 
Combining advanced spectroscopy with low-temperature electrical transport measurements, we have demonstrated wave-like electron transport, exceptionally high carrier mobility, and metallic electronic behavior in polymer crystals. These materials provide a unique platform for investigating quantum transport in soft matter.
We describe this strategy as "molecular and ionic alchemy". Rather than chemically producing metals, we engineer organic materials that reproduce metallic electronic functions through precise control of molecular arrangement and ionic motion. This approach enables lightweight, flexible polymers to acquire metallic properties while preserving the advantages of solution processability and low-temperature fabrication. By integrating synthetic chemistry, electrochemistry, and condensed matter physics, we aim to establish universal design principles for functional organic materials and create sustainable, printable alternatives to conventional metals for future flexible electronic and energy technologies.