کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1399735 | 984489 | 2012 | 6 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Isoprene polymerization using a neodymium phenolate pre-catalyst combined to aluminum based co-catalysts Isoprene polymerization using a neodymium phenolate pre-catalyst combined to aluminum based co-catalysts](/preview/png/1399735.png)
The discrete phenolate Nd(2,6-di-tert-butyl-OC6H3)3 has been assessed as pre-catalyst for the polymerization of isoprene using various aluminum based co-catalysts. In combination with MAO and MMAO in toluene, the reaction is quantitative in 1 h at 60 °C, yielding activities comparable to neodymium versatate and isopropylate in similar conditions. In contrast with the abovementioned systems, the phenolate leads to a single site catalyst species in combination with MAO and MMAO. Increasing amounts of MAO in the reactive medium lead to a decrease of the number–average molecular weight of polyisoprene, highlighting the occurrence of chain transfer between neodymium and aluminum. The polymerization is modestly 1,4-trans selective, in the range 60–75%. Using pentane as a solvent and MMAO, ultra high activities up to 3000 kg PI/mol Nd/h can be reached at room temperature, as well as 85% 1,4-cis selectivity. Ternary systems with co-catalysts based on the chlorinated AlEt2Cl in combination with AliBu3 afford finally a 90–98% 1,4-cis stereoselective polymerization depending on the solvent used for the reaction. The SEC traces are in agreement with the presence of several active species for the latter systems.
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► Neodymium phenolate/aluminum co-catalysts polymerizes isoprene with good to high efficiency.
► Ultra high activity at room temperature in combination with 100 equiv MMAO.
► 98% 1,4-cis stereoselectivity in combination with 40 equiv AliBu3 and 2 equiv AlEt2Cl.
Journal: European Polymer Journal - Volume 48, Issue 7, July 2012, Pages 1289–1294