High yield preparation of uniform polyurea microspheres through precipitation polymerization and their application as laccase immobilization support

Abstract

Uniform polyurea (PU) microspheres were prepared through precipitation polymerization using isophorone diisocyanate (IPDI) as the only monomer in mixed solvent of water-acetonitrile. The highest IPDI loading allowed to have uniform PU microspheres went up to 23wt%, with a high yield of about 95% for the microspheres. The productivity of microspheres thus obtained was about 22 times higher than that by free radical precipitation polymerization, and practically doubled that previously reported on the same polymerization in the mixed solvent of water-acetone. In addition, the polymerization was done under quiescent process with the reactor standing still without any stirring or shaking. TGA and FTIR tests indicated that the microspheres were of high thermal stability with abundant amine group on the surface. As a model enzyme, laccase was immobilized on the surface of the PU microspheres via glutaraldehyde coupling. Compared with the free laccase, the immobilized one exhibited higher activity in alkaline environment and higher thermal stability. The immobilized laccase was used as biocatalyst for degradation of Remazol Brilliant Blue R and showed good decolorization capacity with good reusability. About 65% of its initial catalytic activity was retained after 7 cycles of reuse. This work provides a practically operational protocol for large scale production of uniform PU microspheres, and also demonstrates that these microspheres have promising applications as enzyme immobilization carrier and as biocatalyst in organic dyes degradation.