Synthesis and characterization of partially fluorinated aerogels and xerogels from environmentally-compatible precursors

Abstract

A new fluorocyclic silane monomer was prepared from environmentally benign and commercially available starting reagents in two, high yielding steps. The monomer was characterized by multi-nuclear NMR ( 1 H, 13 C, 19 F, and 29 Si). The monomer was used in the preparation of the first known fluorocyclic aerogels and xerogels. Due to the hydrophobic nature of the fluorocyclic monomer, a modified sol-gel synthesis was utilized in which a minimum amount of water was used. The mol% of the fluorocyclic monomer was systematically varied in both types of silica gels and the effects on the properties of the aerogels and xerogels was analyzed by scanning electron microscopy, BET surface area measurements, differential scanning calorimetry, and thermogravimetric analysis. It was determined that in both aerogels and xerogels, increasing the mol% of the fluorocyclic monomer resulted in condensed materials (i.e., pore collapse). Increased monomer concentration affected the gels thermal stability as the monomer is more susceptible to thermal decomposition than the silica gel. Pore collapse accelerates this effect as the condensed medium dissipates heat less efficiently.

Aerogels from polypyrrole/carbon nanotubes-based polymeric blends

“…7 shows the diameter of the nanotubes, which is approximately 83 nanometers. In the liter-ature, there are reports of aerogels made from TEOS that mention that the pores or internal spaces of the material measure from 50 to 100 nm, coinciding with the pores obtained by us [22].…”

“…Given the great demand for aerogels that can be used for thermal insulation and electrical and mechanical conduction, it would be greatly useful to develop novel, more efficient materials for specific applications. Accordingly, the purpose of the present work was to produce novel aerogels made using a ternary mixture (carbon nanotubes/black smoke/polypyrrole) [18][19][20][21][22], to improve the thermal stability and the mechanical properties of aerogels reported in the literature or commercially-available. Ultrapure CO 2 , Infra SA.…”

Synthesis of Bio‐Based Silane Coupling Agents by the Modification of Eugenol

“…[41] In the third report, the high price of O-perfluorocyclopentenyl substrate limits its application as a starting material for the coupling agent. [42] Taking into account the relatively low toxicity of eugenol, low cost caused by its natural abundance, high thermal stability, and chemical reactivity, this compound has recently been considered as a sustainable alternative for the preparation of high-performance epoxy thermosets, [43] self-healing polymers, [44] flame retardants, [45] coatings, [46] adhesives, [47] or electrode materials for batteries. [48] In this article, we would like to present a simple approach to the synthesis of a new family of biogenic SCAs based on an alkyl-aryl eugenol core, which is obtained by a two-step procedure that involves hydrosilylation of eugenol and its derivatives, and a series of nucleophilic substitution reactions with acyl and alkyl chlorides possessing different groups capable of interacting with polymer chains (i. e., alkenyl, epoxide, thiirane, thiocarbamoyl, thioether, and thioester moieties).…”

“…Although the second method is highly effective, the multi‐step, high‐temperature synthesis procedure of a heterogeneous catalyst which is used, might be problematic [41] . In the third report, the high price of O‐ perfluorocyclopentenyl substrate limits its application as a starting material for the coupling agent [42] …”