Reactive Diazonium-Modified Silica Fillers for High-Performance Polymers

Abstract

We describe a simple way of modification of three silica-based fillers with in situ generated 4-hydroxymethylbenzenediazonium salt (N-CH-CHOH). The rationale for using a hydroxyl-functionalized diazonium salt is that it provides surface-functionalized fillers that can react with phenolic resins. The modification of silica by diazonium salts was assessed using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). FTIR spectroscopy permitted the tracking of benzene ring breathing and C-C. The absence of the characteristic N≡N stretching vibration in the 2200-2300 cm range indicates the loss of the diazonium group. XPS results indicate a higher C/Si atomic ratio after the diazonium modification of fillers and the presence of π-π* C1s satellite peaks characteristic of the surface-tethered aromatic species. Adhesion of aryl layers to the silicas is excellent because they withstand harsh thermal and organic solvent treatments. Phenolic resins (used, for example, as binders in abrasive products) were filled with diazonium-modified silicas at 10-25 wt %. The reactivity of the fillers toward phenolic resins was evaluated by the determination of the flow distance. After annealing at 180 °C, the diazonium-modified silica/phenolic resin composites were mechanically tested using the three-point flexural method. The flexural strength was found to be up to 35% higher than that of the composites prepared without any diazonium salts. Diazonium-modified silica with surface-bound -CH-OH groups is thus ideal reactive filler for phenolic resins. Such filler ensures interfacial chemical reactions with the matrix and imparts robust mechanical properties to the final composites. This specialty diazonium-modified silica will find potential application as fillers in the composites for the abrasive industry. More generally, aryl diazonium salts are a unique new series of compounds for tailoring the surface properties of fillers and tuning the physicochemical and mechanical properties of polymer composites.

Mechanically robust and thermally stable abrasive tools from phenolic resins reinforced with diazonium‐modified zeolites

“…The positive effect of interfacial covalent bonds on the improvement of flexural strength was previously presented in Ref. . Other studies have demonstrated the effect of diazonium modified materials on mechanical properties such as interfacial shear strength (IFSS).…”

“…However, despite remarkable achievements , the diazonium modification of fillers is still sparse This has motivated us to undertake a research work program on the evaluation of aryl diazonium salts for the specific modification of fillers. In this frame, we have shown that the silica fillers modified by diazonium salt with hydroxymethyl groups in the structure had a significant effect on the properties of the phenol‐formaldehyde resin composites . For composites containing diazonium‐modified silica an increase of flexural strength about 35% was achieved in comparison to the composite with unmodified filler.…”

Carbon black modified with 4‐hydroxymethylbenzenediazonium salt as filler for phenol‐formaldehyde resins and abrasive tools

“…This affects the lower possibility of using this method due to the very significant impact of substitution on the properties of the resin . Another possibility of modification to obtain active hydroxymethylbenzene moieties on the surface is the use of diazonium salts . These salts have been used many times before in the modification of many types of carbon structures .…”

Photophysical and Electrochemical Studies of Anchored Chromium (III) Complex on Reduced Graphene Oxide via Diazonium Chemistry

“…The successful modification of sp 2 carbon materials by diazonium chemistry introduced new strategies for the attachment of aryl layers to different organic and inorganic moieties, on account of the applications such as sensing, energy storage systems and molecular electronic junctions . Aryl diazonium compounds perform as precise coupling agents for polymers, biomacromolecules and nanoparticles which are extensively used for catalysis . Modification of materials by diazonium chemistry also provides a well‐defined pathway to design and tune the optical properties for polymers fillers, polymer nanocomposites and polymer sensing layers.…”

“…Modification of materials by diazonium chemistry also provides a well‐defined pathway to design and tune the optical properties for polymers fillers, polymer nanocomposites and polymer sensing layers. This also offers explicit routes to manipulate the nanorobots for cancer probes and drug delivery . Diazonium modification on graphene frame work appears promising since it results in significant increase of room temperature resistance and optical band gap of ~380 meV based on angle resolved photoemission electron microscopy measurements which leads graphene oxide as a potential material in optoelectronics .…”