Wuu-Jyh Liang

Solid polymer electrolytes V: microstructure and ionic conductivity of epoxide-crosslinked polyether networks doped with LiClO4

Abstract A crosslinked polyether network was prepared from poly(ethylene glycol) diglycidyl ether (PEGDE) cured with poly(propylene oxide) polyamine. Significant interactions between ions and polymer host have been observed for the crosslinked polyether network in the presence of LiClO4 by means of FT-IR, DSC, TGA, and 7Li MAS solid-state NMR. Thermal stability and ionic conductivity of these complexes were also investigated by TGA and AC impedance measurements. The results of FT-IR, DSC, TGA and 7Li MAS solid-state NMR measurements indicate the formation of different types of complexes through the interaction of ions with different coordination sites of polymer electrolyte networks. The dependence of ionic conductivity was investigated as a function of temperature, LiClO4 concentration and the molecular weight of polyether curing agents. It is observed that the behavior of ion transport follows the empirical Vogel–Tamman–Fulcher (VTF) type relationship for all the samples, implying the diffusion of charge carrier is assisted by the segmental motions of polymer chains. Moreover, the conductivity is also correlated with the interactions between ions and polymer host, and the maximum ionic conductivity occurs at the LiClO4 concentration of [O]/[Li+]=15.

Synthesis of acrylic copolymers with pendant hydrophilic groups and comparative surface tension studies with corresponding siloxane copolymers

Methyl methacrylate (MMA) and methacrylic acid glycidyl ester (MAGE) have been copolymerized and three water-soluble derivatives of these types of copolymers have been synthesized by opening the epoxide ring with different hydrophilic functional groups like diethanolamine (CHE), quaternary diethylamine (CQDEA) and quaternary diethanolamine (CQHE) The structures have been identified by 1 H and 13 spectra. The behaviors in aqueous medium have been investigated in terms of the surface tension and the ratios of intensities of the fluorescence (I 1 /I 3 ). The results are compared with those of the corresponding water-soluble siloxane copolymers (SHE, SQDEA, SQHE). The plot of I 1 /I 3 as a function of polymer concentration verifies the existence of aggregates and indicates the extent of aggregate formation. It is found that the polymer molecules begin to transfer to the air/water interface before they start to form aggregates for both acrylic and siloxane copolymers. It is evident from the surface tension measurements that efficiency of these polymers to reduce surface tension in aqueous solution is in the order SHE > SQHE > SQDEA and CHE > CQDEA > CQHE. The plots of I 1 /I 3 as a function of polymer concentration show that the ease of formation of aggregates in aqueous solutions of the above-mentioned polymers is in the order SHE > SQDEA > SQHE and CHE >CQDEA > CQHE. The ability of aggregates formation in aqueous solution increases with increasing polymer concentration and the hydrophilicity of the hydrophilic moieties. Moreover, the inner core of these copolymer aggregates is less closely packed than those for usual surfactants like sodium dodecylsulfate (SDS). However, the inner cores of the aggregates of siloxane copolymers in solution are more hydrophobic than those of acrylic copolymers.