SPECIFIC INTERACTION BETWEEN POLY(STYRENE-CO-4-VINYLPHENOL) AND POLY(STYRENE-CO-4-VINYLPYRIDINE) STUDIED BY C-RAY PHOTOELECTRON-SPECTROSCOPY AND TIME-OF-FLIGHT SECONDARY-ION MASS-SPECTROMETRY

The specific interaction of hydrogen bonding between poly(styrene-co-4 -vinylphenol) (STVPh) and poly(styrene-co-4-vinylpyridine) (STVPy) was investigated by X-ray photoelectron spectroscopy (XPS) and time-of-fl ight secondary ion mass spectrometry (ToF-SIMS). The density of the hy drogen bond was adjusted by varying the 4-vinylphenol (VPh) content in the STVPh copolymers. Immiscible blends were formed when the VPh cont ent was low, and an interpolymeric complex was formed when the VPh con tent was above a certain value. In addition, an interpolymer complex w as formed between poly(4-vinylphenol) (PVPh) and STVPy-72 (containing 72 mol % of Py). For the complexes, XPS results revealed that the inte rmolecular hydrogen bonds between the hydroxyl and pyridyl units can i nduce a shift of 0.6-0.7 eV and 0.4-0.5 eV in the N 1s and O 1s bindin g energies, respectively. Such large shifts in the binding energy may imply that the nitrogen is partially protonated. The XPS results also showed that STVPy-72 was enriched on the surface of immiscible blends of STVPy-72 and STVPh-y (where y is the mol % of VPh, y = 1, 9, and 22 ). However, surface segregations of STVPh-50 and PVPh were detected re spectively for the complex between STVPh-50 and STVPy-72 and the compl ex between PVPh and STVPy-72. The intensity ratios of the ions for the complexes that were affected by the formation of hydrogen bonding, su ch as C5H6N+/C5H5N+ and C6H7N+/C6H6N+, were larger than those in the S TVPy-72 copolymer. The intensity ratios of these ions for immiscible b lends of STVPh and STVPy-72 and for the STVPy-72 copolymer were almost the same. The results indicate that hydrogen bonding plays an importa nt role in the distribution of the peak intensities of the ions that a re affected by the formation of hydrogen bonding in a SIMS process.