Self-healable and reprocessable networks involving diblock copolymer and hindered urea bonds

In this contribution, we reported a novel design of the self-healable (and/or reprocessable) networks involving diblock copolymers and hindered urea bonds (HUBs). The diblock copolymers were crosslinked with a cross linker bearing hindered urea bonds (HUBs). Toward this end, a novel crosslinker (denoted HUDA) was synthesized via the reaction of 2-isocyanatoethylacrylate with N,N'-di-tert-butylethylenediamine, a hindered diamine. The diblock copolymers were composed of polystyrene (PS) and poly(n-butyl acrylate-stat-HUDA) [denoted P(BA-stat-HUDA)] blocks, which were synthesized via a two-step sequential reversible addition fragmentation chain transfer (RAFT) polymerization approach. In the P(BA-stat-HUDA) blocks, HUDA acted as not only one of the copolymerization monomers but also the crosslinker bearing HUBs. In the networks, the PS microdomains behaved as the nanoreinforcement of P(BA-stat-HUDA) matrix. It was found that the PS-b-P(BA-stat-HUDA) networks displayed the self-healing properties or/and reprocessing properties. The self-healing properties were quite dependent on the concentration of hindered urea bonds. The self-healing behavior is attributable to the intense metathesis of HUBs in the crosslinked networks.