High-Pressure Synthesis of Highly Conjugated Polymers via Synergistic Polymerization of Phenylpropiolic Acid

The synergistic reaction between alkyne and phenyl groups is a promising pathway for decreasing the reaction pressures of aromatics and enabling scalable high-pressure synthesis of carbon materials via pressure-induced polymerization (PIP). Here by combining theoretical calculations and experimental data, we demonstrate that a simultaneous polymerization of alkynyl and phenyl groups occurred in phenylpropiolic acid (PPA) with the threshold distance d(C center dot center dot center dot C) = 3.3 angstrom, generating an extended structure consisting of sp(2) and sp(3) carbons. The reaction pressure of phenyl was significantly decreased to similar to 5 GPa, which can be applied for large-scale synthesis. The product has a large pi-electron conjugated system, resulting in a band gap energy reduced to 1.65 eV and an electrical conductivity increasing to 1.24 x 10(-6) S.cm(-1). Our research confirmed that conjugated polymers can be synthesized at lower pressures via the high-pressure synergistic reaction route of phenylethynyl compounds and can be used to further realize applications in organic photovoltaic devices.