Properties and surface morphologies of organic–inorganic hybrid thin films containing titanium phosphonate clusters

Abstract

Organic–inorganic hybrid thin films containing [Ti4(μ3-O)(OiPr)5(μ-OiPr)3(O3PPh)3]·THF (TiOPPh) were prepared via the hybridization of TiOPPh with poly(vinyl phenol) (PVP), poly(styrene-co-allyl alcohol) (PSA), and poly(bisphenol A-co-epichlorohydrin) (PBE) using spin coating. These thin films were characterized in terms of their transmittance, pencil hardness, and surface morphologies. The transmittance values of the PVP hybrid thin films decreased with the addition of TiOPPh because of the formation of Ti–O–Ph bonds. The pencil hardness values of the hybrid thin films were in the order PVP > PBE > PSA hybrids. Using confocal laser scanning microscopy and atomic force microscopy, the pencil hardness values were determined to be strongly dependent on the surface morphology, such as the roughness and presence of pin holes. The model cluster was synthesized by the reaction of TiOPPh with excess ethanol to study the structures of the TiOPPh in hybrids. From the nuclear magnetic resonance spectroscopy and single-crystal X-ray structure analyses, the main core structure of the model cluster was found to retain the core structure of TiOPPh. Organic–inorganic hybrid thin films containing [Ti4(μ3-O)(OiPr)5(μ-OiPr)3(O3PPh)3]·THF (TiOPPh) as element blocks were prepared via hybridization with the hydroxyl-substituted organic polymers (PVP, PSA, or PBE) by spin-coating. The hybrid thin films were characterized by AFM, DSC, and pencil hardness. The pencil hardness values of the PVP hybrid thin films were in the order 20 > 40 > 0 wt% and were dependent on the surface smoothness. When TiOPPh was reacted with excess ethanol, the core was retained. Therefore, the core of TiOPPh will be retained in the hybrid polymers.