Abstract
The functionalization of carbon nanotubes (CNTs) plays a key role in their solubilization and compatibility for many applications. Among the many possible ways to functionalize CNTs, the creation of an Si–O–C bond is crucial for the formation of silicone composites. Catalyst-mediated silylesterification is useful in creating Si–O–C bonds because it is cost-effective and uses a hydrosilane precursor of lower reactivity than that of chlorosilane. However, it was previously demonstrated that two important silylesterification catalysts (zinc chloride and Karstedt’s catalyst) exhibit different selectivity for oxidized functional groups that are present on the surface of CNTs after oxidative acid treatment. This report details the selective modification of CNTs with various oxygenated functional groups (aromatic and nonaromatic alcohols, carboxylic acids, ethers, and ketones) using diazonium chemistry. Modified CNTs were used to assess the specifity of zinc chloride and Karstedt’s catalyst for oxygenated functional groups during a silylesterification reaction. Karstedt’s catalyst appeared to be widely applicable, allowing for the silylesterification of all of the aforementioned oxygenated functional groups. However, it showed lower efficacy for ethers and ketones. By contrast, zinc chloride was found to be very specific for nonaromatic carboxylic acids. This study also examined the Hansen solubility parameters of modified CNTs.
Highlights
Carbon nanotubes (CNTs) [1] have exceptional electrical, mechanical, and physical properties [2].their major drawbacks are their insolubility in most common solvents, and their tendency to form aggregates due to strong π–π and van der Waals interactions
Due to the chemical functionalization of CNTs, it is often necessary in order to exfoliate and solubilize them before their practical application [3,4]
One approach consists of the direct functionalization of the CNT sidewall using, for example, carbenes, nitrenes, the Diels–Alder reaction, and diazonium [6]
Summary
Carbon nanotubes (CNTs) [1] have exceptional electrical, mechanical, and physical properties [2].their major drawbacks are their insolubility in most common solvents, and their tendency to form aggregates due to strong π–π and van der Waals interactions. Carbon nanotubes (CNTs) [1] have exceptional electrical, mechanical, and physical properties [2]. Due to the chemical functionalization of CNTs, it is often necessary in order to exfoliate and solubilize them before their practical application [3,4]. One approach consists of the direct functionalization of the CNT sidewall using, for example, carbenes, nitrenes, the Diels–Alder reaction, and diazonium [6]. This option has the advantage of preserving the aspect ratio of CNTs, as well as their mechanical and electrical properties [7].
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