Polymer films of partially phosphorylated poly(vinyl alcohol) (P-PVA) with dipotassium salts have been prepared and characterized, and the effects of phosphorylation on the ionic conduction in the mixed film of P-PVA and polyethylene glycol (PEG: average MW = 200), P-PVA/PEG film, have been investigated. The glass transition temperature (T-g) was significantly decreased by phosphorylation, and it decreased with increasing degree of phosphorylation (DP), indicating an increase in amorphous part on the polymer. For P-PVA/PEG systems, the ionic conductivity increased and activation energy of the ionic conduction decreased with increasing DP, which agreed with the result of T-g. The carrier mobility decreased and carrier density increased with DP. These results indicated that the ionic conductivity of P-PVA/PEG was mainly dominated by the carrier density. Compared with the low molecular weight systems (PVA/K2HPO4/PEG systems), the P-PVA/PEG systems had low T-g, low activation energy and high carrier density, although the ionic conductivity was small at 298.15 K. (C) 2000 Elsevier Science Ltd. All rights reserved.