Organic–inorganic hybrids based on poly(bisphenol A-co-epichlorohydrin) containing titanium phosphonate clusters

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Organic–inorganic hybrid films were prepared by transalkoxylation of poly(bisphenol A-co-epichlorohydrin) (PBE) and titanium phosphonate clusters, such as [Ti4(μ3-O)(OiPr)5(μ-OiPr)3 (O3PPh)3]·thf (Ti4P3), [Ti(OiPr)(acac)(O3PPh)]4 (Ti4P4; acac = acetylacetonato), and Ti7(μ3-O)2 (OiPr)6(μ-OiPr)6(O3PBnBr)6 (Ti7P6). The formation of covalent bonds between PBE and clusters was confirmed by the appearance of νC–O–Ti in the Fourier transform infrared spectra. In addition, the acetylacetonato group in Ti4P4 was dissociated by the hydroxyl group in PBE. The structure of the clusters in PBE was verified by a model reaction of these clusters with alcohols, such as ethanol and isopropyl alcohols, as monitored by nuclear magnetic resonance spectroscopy. The influence of the cluster structure was estimated based on the transmittance, thermal stability, and swelling tests with tetrahydrofuran. The transmittance of the hybrid films was worse than that of pure PBE. The temperature of 5% weight loss (Td5) of the hybrid films was lower than that of pure PBE because Ti–O–C bonding was formed. The solvent uptake of the hybrid films was clearly dependent on the clusters. The swelling ratio increased in the order of Ti7P6 < Ti4P4 < Ti4P3; hence, Ti7P6 showed the highest cross-linking efficiency. We synthesized poly(bisphenol A-co-ephichlorohydrin)–titanium phosphonate clusters (Ti4P3: [Ti4(μ3-O)(OiPr)5(μ-OiPr)3(O3PPh)3]·thf; Ti4P4: [Ti(OiPr)(acac)(O3PPh)]4; Ti7P6: Ti7(μ3-O)2 (OiPr)6(μ-OiPr)6(O3PBnBr)6). From the result of swelling test using tetrahydrofuran, Ti7P6 cluster showed highest cross-linking efficiency.