Structure and mobility in water plasticized poly(ethylene oxide)

The change in structure and mobility of poly(ethylene oxide) (PEO) containing 2 wt% of fumed silica and the water self-diffusion coefficient in concentrated PEO-water systems have been investigated at room temperature in the water weight fraction, w_w, range 0-0.50 w/w. Pulsed field gradient nuclear magnetic resonance was used to measure the self-diffusion coefficients. Structure and mobility properties of PEO were measured with differential scanning calorimetry as well as with positron annihilation lifetime spectroscopy. The largest reduction of the degree of crystallinity of PEO was observed when w_w was increased from 0.13 w/w to 0.50 w/w. Moreover, water induced relaxation of the PEO segments in the amorphous phase, which seemed to have been strained by the crystals during compression molding. The water self-diffusion coefficient increased logarithmically with increased water content below water weight fractions in the amorphous phase of 0.30 w/w and the water molecules were obstructed by the crystalline phase.