Catalysis of isocyanate reaction with water by DMF and its use for fast preparation of uniform polyurea microspheres through precipitation polymerization

• Published in: European polymer journal 2019-06, Vol.115, p.384-390
• Main Authors: Wei, Youyan, Jiang, Xubao, Li, Shusheng, Kong, Xiang Zheng
• Format: Article
• Language: English
• Subjects: Acceleration; Acetone; Catalysis; Catalysts; Composition effects; Copolymers; Diisocyanates; DMF catalysis; Functional microspheres; Isocyanates; Microspheres; Monomer concentration; Polymerization; Polymers; Polyurea; Polyurethane resins; Precipitation polymerization; Solvents; Temperature
• ISSN: 0014-3057; 1873-1945
• DOI: 10.1016/j.eurpolymj.2019.03.054

[Display omitted] •Catalytic effect of dimethylformamide (DMF) observed in isocyanate-H2O reaction.•Mechanism of DMF catalysis in the reaction proposed based on designed experiments.•Preparation of polyurea (PU) microspheres optimized to enhance their productivity.•PU microspheres achieved with higher yield in shorter time in presence of DMF.•PU chemical structure and properties characterized with prospects briefly described. Highly uniform polymer microspheres are widely used for a variety of applications. Uniform polyurea (PU) microspheres have been prepared by precipitation polymerization of isophorone diisocyanate (IPDI) in a binary mixture of H2O-acetone (AT). With AT replaced by N,N′-dimethylformamide (DMF) in the binary mixture, a significant acceleration effect is observed. Through measurements of the solubility of IPDI and its polymer in the binary solvents of different composition, catalytic effect of DMF is confirmed, and a mechanism of catalysis is proposed. The polymerization is carried out at different temperature with varied IPDI concentration in H2O/DMF or H2O/AT/DMF of different composition, with objective to optimize the preparation of PU microspheres. The results demonstrate that, with the polymerization done at 60 °C in a ternary mixture of H2O-DMF-AT, highly uniform PU microspheres are well formed with IPDI concentration of up to 13.0 wt%, which represents an increase of 3 wt% compared to the highest IPDI concentration allowed to have these microspheres in the binary solvent of H2O-AT. This is also accomplished in an obviously shortened time. PU structure and properties are briefly discussed. This work provides a simple and fast protocol for large-scale production of uniform and functional PU microspheres with DMF as a cosolvent and catalyst.