Expanding the chemistry of single‐ion conducting poly(ionic liquid)s with polyhedral boron anions

• Published in: Polymer international 2019-09, Vol.68 (9), p.1570-1579
• Main Authors: Lozinskaya, Elena I, Cotessat, Merlin, Shmalko, Akim V, Ponkratov, Denis O, Gumileva, Lyudmila V, Sivaev, Igor B, Shaplov, Alexander S
• Format: Article
• Language: English
• Subjects: Anions; Boron; closo‐dodecaborate anion; Cobalt; cobalt bis(1,2‐dicarbollide) anion; Copolymerization; Copolymers; Diethylene glycol; Free radicals; Glass transition temperature; Ion currents; Ion exchange; Ionic liquids; Ions; Li batteries; Lithium; Monomers; Organic chemistry; poly(ionic liquid)s; Polyelectrolytes; Polyethylene glycol; Propylene; single‐ion conductors; Stability; Valency
• ISSN: 0959-8103; 1097-0126
• DOI: 10.1002/pi.5878

The synthesis of a new family of single‐ion conducting random copolymers bearing polyhedral boron anions is reported. For this purpose two novel ionic monomers, namely [B12H11(OCH2CH2)2OC(O)C(CH3)CH2]2−[(C4H9)4N+]2 and [8‐(OCH2CH2)2OC(O)C(CH3)CH2‐3,3′‐Co(1,2‐C2B9H10)(1′,2′‐C2B9H11)]−K+, having methacrylate function, diethylene glycol bridge and closo‐dodecaborate or cobalt bis(1,2‐dicarbollide) anions were designed. Such monomers differ from previously reported ones by (i) chemically attached highly delocalized boron anions, by (ii) valency of the anion (divalent anion and monovalent one) and by (iii) the presence of oxyethylene flexible spacer between the methacrylate group and bonded anion. Their free radical copolymerization with poly(ethylene glycol) methyl ether methacrylate and subsequent ion exchange provided lithium‐ion conducting polyelectrolytes showing low glass transition temperature (−53 to −49 °C), ionic conductivity up to 9.1 × 10−7 S cm−1, lithium transference number up to 0.61 (70 °C) and electrochemical stability up to 4.1 V versus Li+/Li (70 °C). The incorporation of propylene carbonate (20–40 wt%) into the copolymers resulted in the enhancement of their ionic conductivity by one order of magnitude and significantly increased their electrochemical stability up to 4.7 V versus Li+/Li (70 °C). © 2019 Society of Chemical Industry Free radical copolymerization of novel ionic monomers bearing boron anions provided lithium‐ion conducting polyelectrolytes with low Tg (−53 °C), ionic conductivity of 9.1 × 10−7 S cm−1, tLi+ = 0.61 and electrochemical stability of 4.1 V versus Li+/Li.