New TiO2 precursor for TiO2:poly(N-vinylcarbazole) (PVK) thin film: Synthesis and reactivity to hydrolysis of titanium tetrakis (9H-carbazole-9-yl-ethyl-oxy)

The chemical reactivity of the ligand initially coordinated on the TiO2 precursor plays a decisive role in the morphology of TiO2:poly(N-vinylcarbazole) (PVK) thin film elaborated by in situ generation of the inorganic phase in the polymer matrix. The final aim of this study is to prepare a new nanocomposite TiO2:poly(N-vinylcarbazole) (PVK) thin film from hydrolysis-condensation of titanium alkoxide in polymer thin film. In this context, we synthesized a new TiO2 precursor, the tetrakis (9H-carbazole-9-yl-ethyl-oxy) [Ti(OeCarb)(4)], bearing ligands close to the repetitive unit structure of the PVK to improve the interaction between both materials. In this study, the synthesis and reactivity to hydrolysis of Ti(OeCarb)(4) is presented. Ti(OeCarb)(4) was elaborated from alcoholysis reaction between titanium isopropoxide [Ti((OPr)-O-i)(4)] and 9H-carbazole-9-ethanol (ECOH) and identified by H-1 and C-13 NMR spectroscopy. The reactivity to hydrolysis-oxolation of Ti(OeCarb)(4) was evaluated first in aqueous media by in situ 1H NMR spectroscopy analysis. Moreover, reactivity of Ti(OeCarb)(4) to surrounding humidity was evaluated in thin film by X-ray photoelectron spectroscopy (XPS). Results show that steric hindrance of 9H-carbazole-9-yl-ethyl-oxide ligands do not influence the hydrolysis-condensation process in aqueous media in our experimental conditions when compared to [Ti((OPr)-O-i)(4)] but decrease the reactivity when the precursor is simply exposed to air humidity. (C) 2009 Elsevier B.V. All rights reserved.