Study of miscibility enhancement in poly(styrene-co-4-vinylphenol)/poly(ethylene oxide) blends by the spin labelling method

The electron spin resonance (ESR) spectra of end-group spin labelled poly(ethylene oxide) (SLPEO) using 2,2,6,6-tetramethyl-piperdine-1-oxyl nitroxide and its blends with poly(styrene-co-4- vinylphenol) (STVPhs) of different hydroxyl contents were recorded over a wide temperature range. For a blend of SLPEO and pure polystyrene (PS), the ESR spectrum was composed of a single motion component, indicating that PS was immiscible with PEO. For blends composed of SLPEO and different- hydroxyl-content STVPhs, two spectral components with different motion rates were observed over a certain temperature range. The difference between the motion rates should be attributed to micro- heterogeneity in the blends, with the faster rate corresponding to a nitroxide radical motion trapped in the PEO-rich domain and the slower rate corresponding to a nitroxide radical motion trapped in the STVPh-rich domain. Variations in the values of a number of the ESR parameters (Ta, Td and T50G )a nd the apparent activation energy (Ea) with hydroxyl content in the blends indicated that the miscibility of the blends increased with increasing hydrogen-bonding density due to specific interactions between the hydroxyl groups in STVPh and the ether oxygens in PEO.  2004 Society of Chemical Industry