Preparation of Highly Uniform Polyurethane Microspheres by Precipitation Polymerization and Pd Immobilization on Their Surface and Their Catalytic Activity in 4-Nitrophenol Reduction and Dye Degradation

Polyurethanes (PUNs) have been widely used in many fields. However, there are few reports on their microsphere preparation through precipitation polymerization. Herein, uniform PUN microspheres are prepared by precipitation polymerization of toluene diisocyanate and trimethylolpropane, without any surfactant and stabilizer. Under optimized conditions, monomers are fully polymerized within 2 h at a monomer concentration as high as 25.0 wt %, with a high yield of the microspheres (96.9%). By loading Pd on their surface, composite microspheres Pd@PUN are obtained and used as catalysts. 4-Nitrophenol is completely reduced within 1 min, with a kinetic constant of 4.96 min(-1), significantly higher than many reported Pd-loaded catalysts, and with comparable reusability. Used in degradation of dye molecules, the catalytic performance is practically unchanged after 20 recycled uses. This work provides a simple method for the preparation of highly uniform PUN microspheres with a high yield and their Pd-loaded catalysts, both of great potential for various applications.