Grafting Amino-Terminated Ionic Liquid to Graphene Oxide Toward Multi-Bonding Synergy for Ultra-High Strength Polyamide 56 Composite Fibers

Polyamide 56 (PA56) is a competitive bio-based polymer but its insufficient mechanical properties restrict its use in advanced applications. Graphene oxide (GO), normally via surface modification toward higher interfacial interaction, is an ideal reinforcing filler for polymers. Herein, an amino-terminated ionic liquid (AIL) is grafted to carboxyl functionalized GO (CGO) with aims to form multi-bonding networks with PA56, including covalent bonding, hydrogen bonding, and electrostatic interaction. The resulting CGO-AIL contains abundant IL at the edge and basal plane of GO, as well as residual carboxyl groups. By filling only 0.2 wt% CGO-AIL to PA56 fiber, the crystallinity of the composite fiber increases from 24.9% to 31.6%. The tensile strength of 0.2% CGO-AIL/PA56 fiber reaches 1555 MPa, which is 3.3 times higher than neat PA56 fiber. For comparison, 0.2 wt% GO and 0.2 wt% CGO only increase the tensile strength to 1211 and 1247 MPa, respectively. This suggests that carboxyl modification brings very limited enhancement for GO/PA56, while IL modification is able to form stronger interfacial interactions for the multi-bonding synergy. This work provides an efficient strategy for the interfacial engineering toward high-strength GO/polymer composites. Highlights Amino-terminated ionic liquid (AIL) is grafted to carboxyl functionalized GO (CGO). The resulting CGO-AIL is filled to PA56 fiber via in situ polymerization. 0.2 wt% CGO-AIL increases the crystallinity of PA56 fiber from 24.9% to 31.6%. Ultra-high tensile strength of 1555 MPa is achieved on 0.2% CGO-AIL/PA56 fiber. The enhancement is for stronger interfacial interaction via multi-bonding synergy.