Mechanically strong and highly stiff supramolecular polymer composites repairable at ambient conditions

Abstract

It is a formidable challenge to fabricate healable polymeric materials with high mechanical strength and stiffness due to the highly suppressed diffusion of their polymer chains. Herein, a high-strength, highly stiff, andrepairable/healablesupramolecularpolymercompositewas fabricatedby complexingpoly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) in aqueous solutions, followed by molding into desired shapes. Exquisitely tuning the electrostatic and H-bonding interactions between PAA and PAH led to associative phase-separation and in situ formation of nanostructures in the resultant PAA-PAH composites. The H-bonded assembly of PAA-PAH complexes existedasnanospheresweredispersedhomogeneously in the continuous phase as an electrostatic assembly of PAA-PAH complexes. Such a structural feature endowed the PAA-PAH copolymer with a doublecross- linked structure, enabling significant reinforcement of the material.a The PAA-PAH composites exhibited a tensile strength and an elastic modulus as highas∼67MPa and∼2.0GPa, respectively.Due tothe benefits from the reconstruction of the complexes, such as reversible electrostatic interactions and H-bonds between PAA and PAH, the PAA-PAH composite could be repaired/healed readily under ambient conditions (25°C, 40% humidity) by using the liquid-like form of the PAA-PAH complexes (i.e., coacervate). The healing strategy reported here provides a supplementary method for easy repair or healing of high-strength and stiff supramolecular polymer materials.