Green Scalable Synthesis of Micrometer-Sized Hydrocalumite with Gas Barrier and UV Shielding Functions

Layered double hydroxides (LDHs) have potential applications in gas-barrier and anti-photoaging fields, yet the fabrication of high-quality micrometer-sized LDHs with low thickness and excellent dispersibility still faces great challenges. Herein, a general green approach for preparing well-dispersed micrometer-sized LDHs is proposed by taking advantage of the easy peptization property of boehmite, the high reactivity of Ca(OH)2, and the high shearing force of a colloid mill. As a proof of concept, micrometer-sized 2-phenylbenzimidazole-5-sulfonic acid (PBSA)-intercalated hydrocalumite (CaAl-LDH) with high crystallinity is synthesized at 90 °C under atmospheric pressure. The existing strong host-guest interactions between the anionic PBSA guests and the LDH host laminates improve the antimigration performance of PBSA guests. Meanwhile, incorporating PBSA-LDH into polyurethane (PU) significantly enhances both the gas barrier and anti-photoaging performance of PU due to the micrometer size and strong ultraviolet absorption capacity of PBSA-LDH. Adding 5 wt % PBSA-LDH reduces the oxygen transmission rate of PU from 2214.3 to 1332.2 cm3·cm-2·day-1 (a decrease of 39.8%) and the photoaging degree of PU by 52.1%. Notably, this strategy can be readily extended to prepare other micrometer-sized hydrocalumite and has good scalability. Therefore, this novel mild green method is efficient in the scalable synthesis of micrometer-sized functional hydrocalumite with practical applications.