| Autor: |
Huang, YiJun, Zhang, XingHong, Hua, ZhengJiang, Chen, ShiLiang, Qi, GuoRong |
| Zdroj: |
Macromolecular Chemistry and Physics; June 2010, Vol. 211 Issue: 11 p1229-1237, 9p |
| Abstrakt: |
Highly active CaCl2modified ZnCoIII DMCs were prepared. XRD results showed that the modified catalyst CaDMC containing 0.14 wt. CaCl2was amorphous. A higher polymer yield >61 kg polymerg catalyst and a shorter induction period for ROP of PO were observed for CaDMC than for unmodified DMC catalysts. An initiator had an inhibitory effect on the initiation and polymerization rate of PO ROP. As the molar ratio of the initiator functionality to the catalyst was increased, the reaction rate and polymer yield decreased, whereas the induction period increased. An increase in reaction temperature tended to reduce the polymer yield and broaden the MWD. The 13C NMR spectrum for an oligomer from a model polymerization without an initiator revealed that the main terminal unit of the polymer was CH2CHCH3OH because H2O in the system participated in reaction initiation. Cl−and tBuOH may also initiate the reaction according to the small amounts of terminal CH2Cl and OCCH33units observed by 13C NMR spectroscopy. On the basis of common characteristics and some new evidence for DMC catalysis, a mechanism similar to a classical coordination insertion process is proposed. |
| Databáze: |
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