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Bifunctional zirconium Schiff base complexes as adhesive, precursor of zirconium-containing polymers, and initiator for lactone polymerizations
Abstract
By taking advantage of the unequal activity of the two NCO groups of toluene-2,4-diisocyanate at room temperature, a pure zirconium coordination compound with two reactive NCO functionalities is obtained, which can function as a precursor for polymerizations with organic primary amines and primary alcohols. A copolymer with poly(tetrahydrofuran) has been formed in this manner. A copolymer of Zr(sal)$\sb4$ (sal$\sp-$ = salicylaldehydato) and 3,3$\sp\prime$-diaminobenzidine, (Zr(tsdb)) $\sb{\rm n},$ which theoretically has one Zr(sal)$\sb2$ end-group and one diamine end-group in an average polymer chain, can strongly adhere to silica and alumina surfaces. To understand the hydrolytic behavior of the Zr(sal)$\sb2$ end-groups in the (Zr(tsdb)) $\sb{\rm n}$ polymer, the hydrolysis of Zr(sal)$\sb4$ has been studied by electronic, vibrational, and proton magnetic resonance spectroscopies. The results show that Zr(sal)$\sb4$ is almost insensitive to moisture in the solid state, but can be hydrolyzed quickly in solution. The adhesion of the (Zr(tsdb)) $\sb{\rm n}$ oligomer on silica or alumina has been further studied by x-ray photoelectron spectroscopy (XPS), including the use of Zr(sal)$\sb4$ as a model modifier. The XPS data show that both Zr(sal)$\sb4$ and (Zr(tsdb)) $\sb{\rm n}$ can strongly adhere to silica and/or alumina surfaces, and the adhesion of (Zr(tsdb)) $\sb{\rm n}$ is probably via both the Zr(sal)$\sb2$ and the diamine end-groups by forming the Zr-O-Si(Al) linkages and the (-NH$\sb2)($SiOH) H-bonds, and the latter may be broken under ultrasonication. Moreover, because (Zr(tsdb)) $\sb{\rm n}$ can initiate the polymerization of $\beta$-($\pm)$-butyrolactone ($\beta$-BL), a detailed study of the (Zr(tsdb)) $\sb{\rm n}$ initiated polymerization of $\beta$-BL has been conducted to clarify the polymerization mechanism. In addition, the polymerization of $\varepsilon$-caprolactone ($\varepsilon$-CL) has been also studied in the presence of (Zr(tsdb)) $\sb{\rm n}$. Model initiators, Zr(sal)$\sb4$ and o-diaminobenzene were used as well for comparison. The results from spectral and chromatographic investigations enable us to propose a dual-site ring-fission mechanism for the (Zr(tsdb)) $\sb{\rm n}$-initiated $\beta$-BL polymerization and a coordination-insertion mechanism for the Zr(sal)$\sb4$-initiated $\varepsilon$-CL polymerization.
Subject Area
Inorganic chemistry|Polymer chemistry|Chemistry
Recommended Citation
Tong, Wenyan, "Bifunctional zirconium Schiff base complexes as adhesive, precursor of zirconium-containing polymers, and initiator for lactone polymerizations" (1993). Doctoral Dissertations Available from Proquest. AAI9408356.
https://scholarworks.umass.edu/dissertations/AAI9408356