Poly(thiourethane-co-ethylene oxide) networks crosslinked with disulfide bonds: Reinforcement with POSS and use for recyclable solid polymer electrolytes

Abstract

In this contribution, we reported the synthesis of the solid polymer electrolytes (SPEs) involving poly(thiourethane-co-ethylene oxide) [denoted P(TU-EO)] and lithium bis(trifluorosulfonyl)imide (LiTFSI). The SPEs were the networks crosslinked with disulfide bonds. First, a linear multi-segmented poly(mercaptothiourethane-co-ethylene oxide) copolymer [denoted P(MTU-EO)] was synthesized via the step-growth polymerization of a difunctional five-membered cyclic trithiocarbonate (D5CT) with equimolar α,ω-diamino-terminated poly(ethylene oxide). Thereafter, the crosslinking of the multi-segmented copolymer was carried out via the radical coupling reaction of thiol groups and the disulfide bonds acted as the crosslinkages. To reinforce the network, octavinyl POSS was introduced and the additional crosslinking was generated via the thiol-ene addition reaction between thiol groups of P(MTU-EO) and vinyl groups of the POSS macromer. It was found that the crosslinking densities increased with increasing the incorporation of POSS. The LiTFSI salt can be well dispersed into the P(TU-EO)-POSS networks and the crystallization of PEO was effectively suppressed. Depending on the molar ratio of ethylene oxide to LiTFSI and the percentage of POSS, the ionic conductivity of the SPEs can reach 2.1 × 10−5 S × cm−1 at 300 K. More importantly, the SPEs can be reprocessed (or recycled) via the dynamic exchange of disulfide bonds.