In the present investigation, we have studied the confined crystallization behaviour of poly (ethylene oxide) (PEO) in electrospun nanofibers which were prepared from immiscible polymer blend of polystyrene (PS) and PEO. The crystallization behaviour of PEO in PS/PEO blend nanofibers were investigated in a wide range of composition from 0.1 to 0.4 using differential scanning calorimetry (DSC) and combine small and wide angle x-ray scattering (SAXS/WAXS). The crystallization of PEO in the as-cast PS/PEO blends occurred exclusively through homogenous nucleation mechanism. However, in the blend nanofibers, when the weight fraction of PEO was ≤0.2, the crystallization of PEO predominantly occurred through homogeneous. The change of nucleation mechanism suggested that the PEO domain volume, dispersed in the PS matrix, was considerably less in the nanofibers. Hence, the number of domains far exceeded the number of inherent heterogeneities present in a given volume of PEO such that in the heterogeneities free PEO domains crystallization could only occur through homogenous nucleation. The small PEo presence of small PEO domain was further confirmed using SEM analysis which also revealed fibril-like domain morphologies of PEO.  Furthermore, the significant depression in the melting point of PEO in the nanofibers suggested that the small PEO volume combined with the confinement imposed by the glassy PS matrix restricted the growth of PEO crystals. This was further confirmed by combined SAXS/WAXS analysis. Moreover, the crystallization behaviour and morphology of thermally annealed nanofiber blends, above the glass transition temperature of PS, was governed by the competition between Plateau Rayleigh instability induced PEO domain break-up and its further coalescence.  <br/>

Homogenous nucleated crystallization of poly (ethylene oxide) under confinement in electrospun nanofibers of polystyrene/poly(ethylene oxide) blends

253rd National Meeting (2017)

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