Grafting hyperbranched polyurethane onto silica nanoparticle via one-pot “A2 + CBn” condensation approach to improve its dispersion in polyurethane

In order to improve the dispersion of silica powder in polyurethane (PU), hyperbranched PU was introduced onto particle surface with coupled NCO-groups by one-pot condensation reaction of “A2 + CBn” monomers, a combination of commercially available 4,4-diphenylmethane diisocyanate (MDI) and diethanolamine (DEOA) or tris-(hydroxymethyl)aminomethane (TOAM). The incorporation of polymers was confirmed by TG/DTA and FTIR analysis. The morphology of silica particles re-dispersed in organic solvent of N,N-dimethylacetamide (DMA) and prepolymer of PU, or kept in diluted reaction suspensions was observed by Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). It was indicated that the dispersion of particles enhanced with grafted polymers attached on surface, and in diluted reaction suspensions or prepolymer of PU, particles dispersion became better than that in DMA. Prepolymer of PU with well-modified silica particles immersed in demonstrated high decomposition temperatures, suggesting an improvement of thermal stability. Hybrid films composed of prepolymer of PU and modified silica particles showed high transmittance in range of near UV and visible light, illustrating the good dispersion of modified silica particles in prepolymer of PU.