Diels–Alder Reactions on Surface-Modified Magnetite/Maghemite Nanoparticles: Application in Self-Healing Nanocomposites

Abstract

Surface-modified inorganic nanoparticles with organic groups allowing thermoreversible cross-linking are versatile building blocks for nanocomposites with improved lifetimes. We studied the synthesis of various organophosphorus coupling agents consisting of phosphonic acid anchor groups, different alkyl spacers (C3, C10), and furan-or maleimide functional groups. The obtained molecules, which are able to undergo Diels−Alder (DA) reactions, were attached to the surface of well-defined preformed magnetite/maghemite nanoparticles by an exchange reaction of the stabilizing oleic acid ligands under mild conditions. A dilution of the reactive functional groups with unreactive methyl phosphonic acid resulted in a cofunctionalization of the surface with nonreactive groups. The reactivity of the modified particle surface toward DA reactions was systematically explored by converting these particles with maleimide/ methylfuran or N-dodecylmaleimide/dodecylfuran. Fourier transform infrared spectroscopy, differential scanning calorimetry, and CHN elemental analysis measurements revealed a correlation between the quantity of functional reagent on the surface and the conversion in DA reactions. DA conversion of the modified particles is higher if fewer sterical hindered molecules react with the surface, which has implications on the use of these particles as cross-linking agents in polymer matrices. A thin nanocomposite film with thermally triggered healing capacity was successfully prepared by cross-linking the particles with 1,1′-(methylenedi-4,1-phenylene)bismaleimide.

Development of Self-Healable Organic/Inorganic Hybrid Materials Containing a Biobased Copolymer via Diels–Alder Chemistry and Their Application in Electromagnetic Interference Shielding

“…For example, conductivity is greatly required for electronic applications such as microelectronics packaging [33], medical devices [34], artificial skins [35], and electromagnetic interference (EMI) shielding [36]. So far, several research studies have been performed to develop DA based nanocomposites, wherein conductive fillers such as metallic nanoparticles [37], carbon nanotubes [38,39,40], and graphene [41,42,43] were incorporated into the material systems. In particular, graphene has attracted a great interest because this two-dimensional carbon allotrope possesses large aspect ratio as well as superior carrier mobility, and can thereby serve as a promising material in EMI shielding technology [43,44,45].…”

Method screening for conjugation of the small molecules onto the vinyl-coated Fe3O4/silica nanoparticles: highlighting the efficiency of ultrasonication

“…Protection of the Fe 3 O 4 NPs against damaging to the core/shell structure, is the most important advantage of one-pot mechanisms such as CA and click chemistry rather than mechanism with successive reactions. They are considered as versatile tools for attaching organic molecules directly onto the surface of nanoscale particles such as silver, iron oxide and diamond [31][32][33].…”

Thermoreversible magnetic nanochains

“…36,37 Moreover, their properties, such as their zeta potential, hydrophobic/-philic character, and ability to interact with other particles, can be tuned by surface modification via ligand exchange. 25,26,38,39 In order to achieve control over the organization and decomposition of the nanostructures, we propose the use of a thermoreversible reaction between ligands. 40 An example of such reactions is the Diels-Alder [4 + 2] cycloaddition.…”

“…41,42 Such a well-known reaction between a conjugated diene and dienophile for forming a substituted cyclohexene derivative can be reversible under certain conditions, [43][44][45][46] which can be further used in the development of self-healing materials. 38,[47][48][49][50][51] In this study, we report a general strategy for MF-assisted organization of individual magnetic NPs into nanochains linked together by thermoreversible covalent bonds (meaning coupling and subsequent thermally induced decoupling). It is a first 'proof of concept' of temperature tunable 'on-off' anisotropic magnetic assemblies.…”