ToF-SIMS study of the surface morphology of blends of polystyrene and poly(N-vinyl-2-pyrrolidone) compatibilized by poly(styrene-co-4-vinylphenol)

The influence of the vinylphenol content of poly(styrene-co-4-vinylphenol) (STVPh) on the surface morphology of a blend of polystyrene (PS) and poly(N -vinyl-2-pyrrolidone) (PVP) was investigated by time-of-night secondary ion mass spectrometry (ToF-SIMS) chemical imaging. The images obtained through the use of the ToF-SIMS positive total ions and selected negative ions cle arly show that the characteristic size of the dispersed phase (PVP) decreas ed with the addition of the STVPh-5 (5 mol.% vinylphenol) random copolymer. The spectra obtained retrospectively from the matrix and the dispersed pha se indicated that the matrix phase was very similar to the pure PS and that the dispersed phase was very similar to the pure PVP. The addition of the STVPh-9 random copolymer to the blend of FS and PVP resulted in a totally d ifferent morphology: both PVP and PS became semi-continuous and the dispers ed particles are much larger. The morphological changes were caused by the formation of a single phase between PVP and STVPh-9 due to an increase in t he density of the hydrogen bond formed between PVP and STVPh-9. When the vi nylphenol content was <2 mol.%, the particle size of the PVP-rich phase sta yed the same. The compatibilizing effect was much weakened as the concentra tion of STVPh-5 decreased to 1 wt.%. Copyright (C) 2001 John Wiley & Sons, Ltd.