MICROPHASE SEPARATION IN AMORPHOUS POLYETHERS COMPLEXED WITH LICLO4, NACLO4, AND NAI

Solubility and glass transition (T(g)) data obtained for amorphous mix tures of LiClO4 with poly(propylene oxide) (PPO) and poly(ethylene oxi de) (PEO), both of molecular weights 4 x 10(3,) confirm that cation-ox ygen binding energy is of lower magnitude in PPO than in PEO. In agree ment with anterior data reported by Moacanin and Cuddihy for a high mo lecular weight PPO, below a critical concentration, which corresponds to a molar ratio O/Li = 10 (O = ether oxygen), a liquid-liquid microph ase separation takes place in the mixtures of the PPO-LiClO4 system. A calorimetric analysis of the DSC data shows that more dilute mixtures of this system consist of microdomains of a fixed composition (O/Li = 10) in equilibrium with salt-free PPO. The same feature applies to th e PPO-NaI system. Further data obtained on amorphous mixtures of PPO a nd PEO with NaClO4 suggest that such a separation phenomenon, which is induced by the long-range Coulombic interactions, is probably a gener al feature of polyether electrolytes. Depending on the balance between these interactions and the cation-oxygen interactions, the complexed components in the present systems separate as either a macroscopic pha se (PPO-NaClO4) or a microphase (PPO-LiClO4 and PPO-NaI) or as more di screte and more labile heterogeneities (PEO-NaClO4).