Design of Luminescent LDH–Polymer Hybrids via Thermally Activated Molecular Pillaring as an Antimigration Strategy for Fluorophores in Polymers

Abstract

In the approach involving the coinsertion of optically active molecules and molecular spacers, only very small amounts of fluorophores are used. These fluorophores must be both well dispersed as well as immobilized to prevent the “aggregation-caused quenching” (ACQ) phenomenon and to ensure efficient and durable optical emission. The inorganic framework of layered double hydroxide (LDH) is known to offer favorable conditions for such requirements. In this study, thermally linkable spacers are used to close the interlayer space of the LDH host, forming a pillared structure that effectively prevents the migration of organic fluorophores out of the host layers. By using vinylbenzenesulfonate (VBS) or sulfopropyl methacrylate (SPMA), optimal external photoluminescence quantum yields (PLQY_ext) are achieved with sulforhodamine B (SRB), even at relative loadings as low as 0.01 mol % and 0.03 mol % of LDH’s anion exchange capacity. For practical applications, such as in optics, the luminescent LDH powders are dispersed within a polymer matrix, where a major challenge lies in preventing fluorophore migration. The confinement provided by the present system is remarkable, as no trace of fluorophore was detected even under harsh accelerated migration tests.