Ionic conductivity of complexes of novel multiarmed polymers with phosphazene core and LiClO4

Abstract

Novel multiarmed polymers with ethylene oxide units, [( CH2CH2O)n: 7, n = 3; 8, n= 7.2; 9, n = 11.8, and 12, n = 11.8] were prepared from the reaction of polyethylene glycol monomethyl ethers with acid chlorides of hexakis(3,5-dicarboxyphenoxy)-(6) and hexakis(4-carboxyphenoxy)cyclotriphosphazenes (11) and conductivities of their Li+ salt complexes were investigated. The glass transition temperatures of the salt-free polymers are in the temperature range −59 to −54°C, indicative of a high degree of reorientational mobility of the arms. When LiClO4 was added to the multiarmed polymers, the Tg values raised monotonically. The extent of Tg elevation was affected by the length of arms and the number of oxygen atoms around cyclotriphosphazene core and increased in the order 7 > 8 > 12 > 9. The conductivities increased in the order 9 > 8 = 12 > 7 and the maximum conductivities of 4.0 × 10−5 S/cm at 30°C and 6.0 × 10−4 S/cm at 90°C have been achieved for the 9-Li+ complex with Li+/O = 0.03. Interestingly, the conductivity of 9-Li+ complexes at constant reduced temperatures increased in the whole concentrations of LiClO4 examined (Li+/O = 0.01–0.2), although the degree of increase in conductivity above Li+/O = 0.06 became small. From the behaviors of Tg and the conductivity of multiarmed polymer–LiClO4 complexes, it appears that the conductivity is governed by relative concentrations of inter- and intramolecular complexes in the polymer matrix. The influence of structural change of the comb-shaped to multiarmed polymers on the conductivity is described. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1839–1847, 1997