Click chemistry promoted by graphene supported copper nanomaterials

Abstract

A facile and robust approach is provided for the synthesis of highly dispersed copper nanoparticles immobilized onto graphene nanosheets, useful as a recyclable and reusable heterogeneous catalyst with excellent catalytic activity to achieve Cu(I)-catalyzed [3+2] cycloaddition 'click' chemistry.

“Click”‐Triggered Self‐Healing Graphene Nanocomposites

“…To enhance the mechanical properties and to improve the dispersion of the copper catalyst, graphene‐immobilized copper(I) (TRGO‐Cu 2 O) was synthesized. [21b] TEM and STEM investigations (Figure j–m) and XPS analysis (Figure S1, Supporting Information) confirm that graphene‐immobilized copper is in the form of Cu(I) as required for successful “click” chemistry. To investigate the click‐based polymer‐network formation (Figure f), and to verify the activity of different catalysts in the epoxy matrix, differential scanning calorimetry (DSC) of mixtures composed of component 1 and 2 , together with the respective homo‐ and heterogeneous Cu(I) catalysts, was performed.…”

“…The obtained results confirm a low temperature network formation in the presence of commercially available homogeneous (Cu(PPh 3 ) 3 F, and Cu(PPh 3 ) 3 Br), and the heterogeneous (TRGO‐Cu 2 O) catalysts, where crosslinking happened at around T onset ≈ 55 °C, and T p = 59 °C, respectively, compared to the thermally triggered click reaction, which occurred at T onset = 99 °C, and T p = 133 °C. [21a] Subsequently, the stability of components 1 and 2 in the epoxy matrix was evaluated. Therefore, DSC measurements were run with different loadings of healing components (10, 20, and 30 wt%) dispersed in the precured epoxy matrix (Figure l,n), where a linear enthalpy of crosslinking was observed with respect to the concentration of the healing components (Figure S2a, Supporting Information).…”

“…Thus, the results demonstrated a higher catalytic activity of TRGO‐Cu 2 O in comparison to homogeneous copper(I) catalysts, related to the scaffold properties of the applied graphene sheets, which prevent the agglomeration of copper particles (Figure h). [21b], Additionally, the unique interactions of metal particles with graphene, including its ability for electron capture and transport, were helpful to boost the catalytic activity of graphene supported metal particles . In contrast, an agglomeration of the homogeneous Cu(I)‐catalysts in the epoxy matrix was observed (Figure S4, Supporting Information), which further emphasizes their limited self‐healing performance compared to their heterogeneous counterpart.…”

“…Synthesis : Trivalent azide 1 and trivalent alkyne 2 [21a] (Figure a,b) were prepared according to previously reported methods.…”

“…The used components 1 and 2 can be encapsulated as liquids via an interfacial embedding process, transmitting stability over months within the capsules. Furthermore the use of graphene as a stabilizer for the Cu(I)‐species expects an enhanced catalyst dispersion along with graphene‐based reinforcement of the mechanical properties for the resulting nanocomposites …”