Ion conducting solid polymer electrolytes based on polypentafluorostyrene-b-polyether-b-polypentafluorostyrene prepared by atom transfer radical polymerization

Abstract

Novel triblock copolymers based on central poly(ethylene glycol) (PEG) or poly(ethylene glycol-co-propylene glycol) (PEGPG) blocks with poly(pentafluorostyrene) (PFS) outer blocks were prepared by Atom Transfer Radical Polymerization (ATRP) with polydispersities on the order of 1.2–1.3. The bromoisobutyrate functionalized polyether macroinitiators with molecular masses (M_n) of approx. 10000 enabled the addition of between 15 and 39 wt.% flanking PFS as found by ¹H NMR. In a similar fashion monomethoxy PEG (MPEG, M_n 5000) was added 50 wt.% PFS. Polymer electrolytes were prepared by complexing lithium bis(trifluoromethylsulfonyl)imide salt with the block copolymers and the liquid PEGPG precursor. The crystallinity and the melting points of the salted MPEG-b-PFS and triblock copolymers were found by DSC to be substantially suppressed. Short PFS blocks (T_g 33 °C) and the salted PEGPG blocks (T_g −65 °C) were immiscible and resulted in phase separation providing an elastomeric material in form of a physically cross-linked polyether network, even when the PFS block consisted of only about four monomer units. The salted triblock copolymers of PEGPG demonstrated conductivities of 10^−5.1 to 10^−4.9 S cm⁻¹ at 20 °C.