Spirocycles as stable alternative of networks—polycondensations of oligoether diols with metal tetraalkoxides
| Autor: | Hans R. Kricheldorf, Simon Rost |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Zirconium
Condensation polymer Materials science Polymers and Plastics Organic Chemistry technology industry and agriculture chemistry.chemical_element macromolecular substances chemistry.chemical_compound chemistry Polymerization Alkoxide Polymer chemistry Materials Chemistry Chemical stability Tin Ethylene glycol Tetrahydrofuran |
| Zdroj: | Polymer. 45:3205-3213 |
| ISSN: | 0032-3861 |
| DOI: | 10.1016/j.polymer.2004.02.059 |
| Popis: | Germanium, tin, titanium and zirconium tetraalkoxides were polycondensed with poly(ethylene glycol)s (PEGs) and poly(tetrahydrofuran) (PTHF) diols at temperatures between 100 and 200 °C. The lengths of the diols were varied from PEG-300 over PEG-400, PEG-600 and PEG-1000 to PEG-2000. In the case of PTHF diols number average molecular weights ( M n s) of 650, 1000 and 2000 were used. When Ge(OEt) 4 was polycondensed, all reaction products were soluble. In the case of Sn(OtBu) 4 , all products obtained from diols with M n s ≥600 Da were soluble, whereas a stiff gel was obtained from PEG-400. From Ti(OnBu) 4 and Zr(OEt) 4 soluble spirocycles were only obtained for diols with M n s≥1000, whereas the shorter diols yielded stiff networks. In the case of Ti(OnBu) 4 and PEG-1000, it was observed that at temperatures ≤120 °C initially a stiff gel was formed obviously by a kinetically controlled polycondensation. Upon heating to 140 °C this gel underwent an irreversible transformation into syrupy, soluble spirocycles due to equilibration of Ti–O–R bonds. The thermodynamic stability of the spirocycles is explained by strain-free rings and a gain in entropy. Preliminary experiments with the spirocycles of zirconium proved their usefulness as initiators for the ring-expansion polymerization of e-caprolactone. |
| Databáze: | OpenAIRE |
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