Preparation Of Porous Polyurea Microspheres And Their Application

Highly uniform porous polyurea microspheres were prepared through precipitation polymerization using isophorone diisocyanate(IPDI) as monomer and SiO2 nanoparticles as template in the mixture of H2O/ acetone at mass ratio of 3/7, and followed by removing SiO2 naoparticles using NaOH solution. Particle size, size distribution and amine content of porous polyurea microspheres prepared in the different experiment conditions were determined. The optimal amount of NaOH solution and operation time during the process of removing SiO2 nanoparticles were studied. Results showed that isocyanate group was dispeared after polymerization conducted for 4 h. When polyurea/SiO2 composite microspheres were placed in the NaOH solution after 18 h as the molar ratio of NaOH to SiO2 was 10, SiO2 particles were all removed. Uniform polyurea microspheres could be prepared without addition of SiO2 particles when polymerization temperature was 30 oC and IPDI amount was 3 wt% of all substances mass. With the addition of SiO2 particles, uniform polyurea/SiO2 composite particles and porous polyurea microspheres could be obtained when the polymerization temperature from 30 oC to 50 oC. Monodisperse porous polyurea microspheres could be obtained when SiO2 particles mass was less than 140 wt% of IPDI mass. Uniform porous polyurea microspheres with particle size from 1.88 to 10.0 μm can be prepared by changing IPDI concentration. Pore size of porous polyurea microspheres can be controlled by changing the size of SiO2 particles. And amine group content of the porous polyurea microspheres was between 0.66 and 1.86×10-4 mol/g.The uniform porous polyurea microspheres were functionalized by glutaraldehyde via the amines on the surface of the porous microspheres. Laccase and lipase were immobilized to the functionalized uniform porous microspheres via covalent binding, repectively. The activity of the laccase and lipase immobilized on the porous microspheres were measured, and comparied to free laccase and lipase.Using diammonium 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonate(ABTS) as the substrate of the catalytic reaction, the activity of the free laccase and immobilized laccase was studied. Results indicated that 0.4629 mg laccase can be immobilized to 1 mg porous microspheres when immobilization temperature was 40 oC, pH was 4.0, and reaction time was 4 h. The activity of free laccase was 4.6699 U/mg while the activity of the immobilized laccase was 0.5857 U/mg as the catalytic reaction temperature was 30 oC and pH was 4.0. So the retained activity of the immobilized laccase on the porous microspheres was only about 12.54% of free laccase. The immobilized laccase kept very low activity.Using p-Nitrophenyl palmitate as the substrate of the catalytic reaction, the activity of the free and immobilized lipase was studied. Results indicated that 0.7544 mg lipase can be immobilized to 1 mg porous microspheres when immobilization temperature was 30 oC, pH was 8.0, and reaction time was 6 h. The activity of free lipase was 40745 U/g while the activity of the immobilized lipase was 32665 U/g as the catalytic reaction temperature was 50 oC. So the retained activity of the immobilized lipase on the porous microspheres was about 80.17% of free lipase. The immobilized lipase had high activity.