Innovative Hyperbranched Polybenzoxazine-Based Graphene Oxide—Poly(amidoamines) Nanomaterials

Abstract

The covalent functionalization of graphene oxide (GO) surface with hyperbranched benzoxazine (BZ) structures has been achieved using poly(amidoamine) dendrimers (PAMAM) of different generations. By increasing the PAMAM generation, multiple benzoxazine rings were synthesized decorating the GO layers. The polymerization process and the exfoliation behavior were investigated. The novel BZ-functionalized GO hybrid materials were characterized by a combination of techniques such as FT-IR, XPS, and 1H-NMR for the confirmation of benzoxazine formation onto the GO layer surfaces. Raman and XRD investigation showed that the GO stacking layers are highly disintegrated upon functionalization with hyperbranched benzoxazine monomers, the exfoliation being more probably to occur when lower PAMAM generation (G) is involved for the synthesis of hybrid GO-BZ nanocomposites. The polymerization of BZ rings may occur either between the BZ units from the same dendrimer molecule or between BZ units from different dendrimer molecules, thus influencing the intercalation/exfoliation of GO. DSC data showed that the polymerization temperature strongly depends on the PAMAM generation and a significant decrease of this value occurred for PAMAM of higher generation, the polymerization temperature being reduced with ~10 °C in case of GO-PAMAM(G2)-BZ. Moreover, the nanoindentation measurements showed significant mechanical properties improvement in case of GO-PAMAM(G2)-BZ comparing to GO-PAMAM(G0)-BZ in terms of Young modulus (from 0.536 GPa to 1.418 GPa) and stiffness (from 3617 N/m to 9621 N/m).

Study of the dielectric heating of graphite oxide and its effect on the microwave‐assisted synthesis of Nylon‐6/graphite oxide polymeric hybrid nanocomposites

“…Same case to rGrOF‐Ny where the aforementioned peaks appear at 400.5, 399.8, and 399.1 eV. These findings reveal the grafting of Nylon‐6 chains onto the graphene hexagonal network 42,44 . This covalent bonding is confirmed by the analysis of the C 1s peak, where the spectrum of GrO (Figure 9d) shows the peaks of its characteristic functional groups of C═C/CC, CO, COC, C═O, and O═COH, 57 which disappear in the spectrum of rGrOP‐Ny and rGrOF‐Ny (Figure 9e,f).…”

“…These findings reveal the grafting of Nylon-6 chains onto the graphene hexagonal network. 42,44 This covalent bonding is confirmed by the analysis of the C 1s peak, where the spectrum of GrO (Figure 9d) shows the peaks of its characteristic functional groups of C═C/C C, C O, C O C, C═O, and O═C OH, 57 which disappear in the spectrum of rGrOP-Ny and rGrOF-Ny (Figure 9e,f). In addition, the hybrid materials exhibit the peaks related to chemical grafting with Nylon-6 chains such as C C═O, C N, and O═C NH.…”

“…On the other hand, the absence of signals corresponding to GrOP suggests a complete exfoliation during polymerization 41 that is attributed to its interlamellar spacing (9 and 10 Å) and its dimensions (5 nm–250 μm) 42 . SEM studies reveal that Nylon‐6 chains graft and crystallize on the surface of rGrOF‐Ny and rGrOP‐Ny, preventing the reordering of the sheets and increasing their d ‐spacing 43,44 . Moreover, the grafted polymer induces the film formation by acting as a bond between the sheets 39 …”

“…Besides, their low molecular weight accentuates this effect. [53][54][55] To confirm the chemical grafting in rGrOP-Ny and rGrOF-Ny specimens, XPS studies were performed where the survey spectra (Figure 9a) GrO initially shows the characteristic signals of O and C at 531 and 283 eV, 44,56 but rGrOP-Ny and rGrOF-Ny, reveal an additional signal of N at 397 eV.…”

“…42 SEM studies reveal that Nylon-6 chains graft and crystallize on the surface of rGrOF-Ny and rGrOP-Ny, preventing the reordering of the sheets and increasing their d-spacing. 43,44 Moreover, the grafted polymer induces the film formation by acting as a bond between the sheets. 39 To further study the exfoliation of GrOF, a set of polymerizations was performed applying higher irradiation powers (400 and 500 W) in which the DH of the film increased considerably, causing an explosion before the melting of the monomer (Figure S10).…”