Synthesis and analysis of a healable, poly(propylene glycol)-based supramolecular network

Abstract An investigation into healable supramolecular networks based upon branched poly(propylene) (PPG) oligomers that feature nitroarylurea chain ends is reported. A one-pot reaction utilising bis(toluene-1,4-diisocyanate)-terminated poly(propyleneglycol) (M n ∼ 2300), a nitroarylurea recognition motif, and tris(2-aminoethyl)amine was used to synthesise several branched PPG-based oligomers. The degree of oligomerization/branching was systematically varied by changing the stoichiometry of the starting materials in this one-pot reaction. The branched oligomers thus generated self-assemble into supramolecular networks, aided by association of the nitroarylurea end groups, and from this study a material that is capable of healing at ambient temperatures was realised. The healable supramolecular material formed from these studies exhibited effective autonomous healing (80% with respect to ultimate stress) up to 6 weeks after defect formation. Furthermore, elastic recovery was observed (80% with respect to yield stress) over a period of 24 h after the samples were elongated beyond the region of uniform strain (50%).