Modular Synthesis and Interface Engineering of Guest–Host Polymers Containing Highly Asymmetrical Push–Pull Heptamethines for Electro-Optics

Push–pull heptamethine chromophores (PPH-phores) containing Michler’s base donor moieties exhibit limited solubility and low loading density during film processing of guest–host electro-optic (EO) polymers. To address the issues, we designed and synthesized asymmetrical derivatives of Michler’s base through steric and electronic modifications, yielding 11 highly asymmetrical PPH-phores that incorporate various meso -substituents and strong tricyanofuran acceptors. These diverse structural variations regulate the electronic polarization and solution processability of the PPH-phores, further determining their first hyperpolarizabilities (β values) and optimal loading densities in guest–host polymers. The approach effectively increased the loading levels of PPH-phores in poled guest–host polymers by 23%, resulting in a substantial enhancement in the EO coefficients ( r 33 values) of the materials. Furthermore, for high-field poling of sandwiched EO polymer films, inserting a solution-processable ultrathin SnO 2 barrier layer dramatically reduced the leakage current during poling, thereby improving the poling efficiency of guest–host films. Together, the modular synthesis and interface engineering presented in this study achieved large r 33 values, up to 149.1 pm/V at 1304 nm, from the poled films containing highly asymmetrical PPH-phores, representing the best EO activities to date for PPH-phores in poled polymer systems.