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Preparation of poly(ethylene oxide) film with variation of drying temperature

Different applications of polymers demand different processing procedures, among which is the film preparation for solid polymer electrolyte (SPE) by solution casting technique. Solution casting technique is widely used technique to prepare flexible films of SPE with different thickness. The main obstacle is to prepare films without solvent residue, that is primarily connected to the drying procedure. Poly(ethylene oxide) (PEO) as water-soluble and biodegradable polymer is one of the polymers that is used as the host polymer for a salt and other additives to prepare SPE [1]. Since the ionic conductivity in PEO with lithium salts was discovered, the significant effort was devoted to preparation of a good quality film with higher conductivity value. This can be improved by lowering the amount of crystalline phase because the ionic transport is correlated with amorphous phase that is preferred for the faster ion transfer [1]. The procedure of the film preparation can influence the crystallinity of the film. PEO films with different PEO molecular weights (100 000 and 300 000 g mol-1) were prepared by casting the films from the aqueous solutions of different PEO concentrations (1 and 1.5 wt%). The optimal conditions for dissolving the polymer in water was found. Successfully prepared solutions were casted and dried at 40, 50 and 60 °C, to find the optimal drying conditions. Films with higher molecular weight has better quality. Differential scanning calorimetry (DSC) was applied to investigate the influence of different molecular weights, film thicknesses and drying temperatures on the thermal properties and crystallinity of PEO. The formation of different PEO crystals was observed, and in general it can be concluded that thermal characteristics of the films doesn’t differ significantly. The thermal stability of the films was investigated using non-isothermal thermogravimetry (TG). PEO films decompose in one decomposition stage and there is no large difference in the thermal stability by variation of the molecular weight, film thickness or drying temperature, with one exception. Due to the successful removal of the solvent from the dried films at 40 °C, it is not necessary to use a higher temperature but only to investigate the minimum drying time to optimize the preparation procedure.

poly(ethylene oxide), film, solution casting technique, drying temperature

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