Surface characterization of poly(styrene-co-p-hexafluorohydroxyisopropyl-α-methylstyrene)/poly(4-vinylpyridine) blends spanning the immiscibility-miscibility-complexation transition by XPS, ToF-SIMS, and AFM

X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and atomic force microscopy (AFM) were used to investigate the surface composition, structure, and morphology of various poly(styrene-co-p-hexafluorohydroxyisopropyl-alpha-methylstyrene)/poly(4-vinylpyridine) (PS(OH)/PVPy) blends spanning the immiscibility-miscibility-complexation transition, when the density of the hydrogen bond was adjusted by varying the hydroxyl content of the PS(OH) component. The surface chemical composition of the blends has been shown to be strongly dependent on the density of the hydrogen bonds. XPS results revealed that the intermolecular hydrogen bonding between PS(OH) and PVPy could induce a shift of 0.9-1 and 1.2-1.3 eV in the N 1s and O 1s binding energies, respectively. ToF-SIMS data showed that the absolute intensity of positive secondary ions characteristic of PVPy at m/z = 80, 93, 106, and 120 was enhanced due to the formation of hydrogen bonds. The hydroxyl groups enhanced the formation of pyridine-ring-containing ions, which need one proton in the process of ion fragmentation. The positive ions at m/z = 132, 195, and 209, which are also characteristic of PVPy, showed little enhancement because these ions contain unsaturated double bonds. ToF-SIMS and AFM results showed that the size of the dispersed phase decreased as the density of the hydrogen bond increased.