Polyamine crosslinked with diisocyanates: Reprocessing, shape recovery and polyelectrolyte properties

A linear polyamine (PEA) was synthesized and then crosslinked with diisocyanates. The crosslinking led to the integration of benzyl hindered urea bonds (HUBs) into the PEA networks. First, the Schiff base reaction of terephthaldicarboxaldehyde with a polymeric diamine bearing poly(ethylene oxide) (PEO) block was carried out to generate a linear poly(ether imine), which was then transformed into the PEA through hydrogenation reaction. By taking control of types and contents of diisocyanates, the PEA networks were regulated displaying variable thermomechanical properties. More importantly, the PEA networks can be reprocessable (or recyclable); the dynamic exchange of benzyl HUBs was responsible for the excellent reprocessing (recycling) properties. Thanks to the crosslinking, the PEA networks had the shape memory properties featuring the reconfigurability. Benefiting from the integration of PEO blocks, the PEA networks can be converted into the solid polyelectrolytes (SPEs). Incorporated with an electrolyte [e.g., lithium bis(trifluoromethanesulphonyl)imide, LiTFSI], the networks can have the ionic conductivity as high as 7.1 × 10⁻⁵ S × cm⁻¹ at 300 K. Notably, the SPEs integrated with benzyl HUBs were recyclable without sacrificing the ionic conductivity.