Construction and Mechanism Analysis of a Self-Assembled Conductive Network in DGEBA/PEI/HRGO Nanocomposites by Controlling Filler Selective Localization

Abstract

Herein, a feasible and effective approach is developed to build an electrically conductive and double percolation network-like structure via the incorporation of highly reduced graphene oxide (HRGO) into a polymer blend of diglycidyl ether of bisphenol A/polyetherimide (DGEBA/PEI). With the assistance of the curing reaction-induced phase separation (CRIPS) technique, an interconnected network of HRGO is formed in the phase-separated structure of the DGEBA/PEI polymer blend due to selective localization behavior. In this study, HRGO was prepared from a unique chemical reduction technique. The DGEBA/PEI/HRGO nanocomposite was analyzed in terms of phase structure by content of PEI and low weight fractions of HRGO (0.5 wt.%). The HRGO delivered a high electrical conductivity in DGEBA/PEI polyblends, wherein the value increased from 5.03 × 10−16 S/m to 5.88 S/m at a low content of HRGO (0.5 wt.%). Furthermore, the HRGO accelerated the curing reaction process of CRIPS due to its amino group. Finally, dynamic mechanical analyses (DMA) were performed to understand the CRIPS phenomenon and selective localization of HRGO reinforcement. The storage modulus increased monotonically from 1536 MPa to 1660 MPa for the 25 phr (parts per hundred in the DGEBA) PEI polyblend and reached 1915 MPa with 0.5 wt.% HRGO reinforcement. These simultaneous improvements in electrical conductivity and dynamic mechanical properties clearly demonstrate the potential of this conductive polyblend for various engineering applications.

Enhanced Electromagnetic Interference Shielding Properties of Immiscible Polyblends with Selective Localization of Reduced Graphene Oxide Networks

“…Figure 4 a,d represents the inversion phase structure of DP25R3 and DP30R3, respectively. The phase structure of DP25R3 is changed from the co-continuous phase morphology of DP25 to the inversion phase morphology [ 14 ]. This change may be caused by the amino groups from RGO, which stimulate the CRIPS [ 19 ].…”

“…The peaks of DP30 at ~1476, 1361, 1101, and 744 cm −1 correspond to aromatic ring stretching, C–N stretching (in phthalimide rings), Ar–O–Ar stretching, and C–N bending (in phthalimide rings) vibrations, respectively [ 39 , 40 ], which are not visible in neat DGEBA or DR3. In comparison with DP30, however, DP30R3 does not show a significant decrement in the peak intensities at ~1658 and 1573 cm −1 , which are associated with C=N and –NH 2 stretching, respectively, and are formed by hydrazine reduction of RGO [ 14 ], due to the low content of RGO in the polyblend. The PEI chains might more efficiently interact with RGO through non-bonding interactions such as electrostatic, dipole, and π-π stacking interactions between PEI and RGO basal plane [ 41 ].…”

“…The values of ω a from both the harmonic and geometric methods are close to 1, indicating the two possibilities of selective localization for RGO according to different RGO content. In our previous work with 0.5 wt.% RGO in nanocomposites [ 14 ], the prediction using the harmonic method showed that RGO selectively localized at the interface. However, by increasing the content of RGO to 3 wt.% in this work, a few RGO entered the DGEBA phase close to the interface, as predicted by the geometric method, due to the limitation of the interface and the strong interfacial tension of DGEBA.…”

“…The preparation of RGO was according to a previous publication [ 14 ]. The RGO suspension was then filtered and washed by DMF for three times to remove the unreacted reducing agent (i.e., hydrazine).…”

“…To form conductive networks with low percolation, it is necessary that the nanofiller be localized at the interface of the separated polymer phases in co-continuous or phase inversion polyblend with the balanced mechanical properties of two integrated polymers [ 13 ]. When the polyblend system contains a thermosetting polymer such as diglycidyl ether of bisphenol A (DGEBA), the curing reaction can control the localization of the nanofiller at the interface of two immiscible polymers [ 14 ]. Other than the thermodynamics of curing reaction, various kinetic and rheological factors also influence the final phase structure of the polyblend and preferential localization of fillers.…”