Waterborne Colloidal Polymer/Silica Hybrid Dispersions and Their Assembly into Mesoporous Poly(melamine-formaldehyde) Xerogels

Abstract

The acid-catalyzed polycondensation of oligo-(melamine-formaldehyde) in aqueous phase and in the presence of silica nanoparticles leads to a stable dispersion of coexisting silica and polymer nanoparticles. The dispersion can be processed into mesoporous xerogels (S BET ≈ 200 m 2 g −1 ), whose porosity can be enhanced by etching of silica up to specific surface areas of >400 m 2 g −1 . The formation mechanism and the characteristics of the hybrid dispersion are crucial to the materials derived from it and analyzed in detail using a variety of experimental techniques (electron and force microscopy, light and X-ray scattering, ultracentrifugation, and spectroscopy). The transformation of the dispersion into xerogels by electrostatic destabilization is described. Furthermore, the obtained materials are characterized with regard to their porosity and morphology using microscopy and porosimetry. The impact of selected synthesis parameters on the obtained properties is discussed, and it was found (most interestingly) that stable porosity was only observed if silica nanoparticles were present within the dispersion.

Simple synthesis of porous melamine-formaldehyde resins by low temperature solvothermal method and its CO2 adsorption properties

“…Among them, the porous melamine-formaldehyde resins (PMFRs) have gained great attention because they can be produced by low-cost highly abundant melamine that has suitable alkalescence (pKa = 5.5) versatile reactivity [28][29][30]. In addition, it is a mass produced product in the chemical industry and can be used as crosslinker in organic coating and plastic [31][32][33]. In general, the PMFRs can be synthesized by using the microemulsion approach or the template method, such as SiO 2 particles [34].…”

Melamine-formaldehyde-silica and melamine-silica-cellulose composites in removing Iron and N-ammonia from landfill leachate

“…Silica nanoparticles are homogeneously distributed within the PMF matrix. The presence of silica nanoparticles and not agglomerates, in addition to the uniform distribution, allows the PMF-Si composite to have better stability and better water absorption capacity by the hydrogel (Schwarz & Weber, 2015). Figure 4d at 200 nm scale shows in the upper left corner the network structure of the PMF present in the hydrogel.…”