Synthesis of end-functionalized polyethylene via catalysed chain growth reaction Jiakai Huang 2 , George Britovsek 1 1 Imperial College London and 2 Imperial College London, China Functional polyolefins are highly desired materials, due to their beneficial surface properties, especially polymers bearing polar functional groups. Compared to those non-fucntionalized analogues they exhibit properties with respect to adhesion, toughness, miscibilty and rheological properties. A method to synthesize highly reactive Zn(PE) 2 species, which can be further reacted to produce end-fucntionalized polyethylene, has been previously established. 1
With the help of methylaluminoxane as a co-catalyst and diethyl zinc as the chain transfer reagent, the chain length of the final polymer and the molecular weight distribution can be controlled by utilizing the radio of catalyst, methylaluminoxane and diethyl zinc. Multiple chemicals have been tried to quench Zn(PE) 2 , and iodine and acyl chloride species are found to be the most suitable chemicals to quench the reaction to generate high quality and functionality product. Reactive Zn(PE) 2 can be converted polyethylene iodide directly when excess of iodine is used as the quenching reagent. Polyethylene iodide can be used as a starting material for further functionalization, and some research group has attempted to use sodium azide and lithium aluminum hydride to convert polyethylene iodide to polyethylene amine. 2 However, these chemicalsare quite dangerous and not easy to handle in the lab, but we have successfully utilized liquid ammonium as a nitrogen source to convert halide group to an amine group with a satisfied yield in an autoclave.
Polyethylene amine can be converted to a PE-PNP type material, and a polyethylene bounded Cr(PNP) system can be prepared from it, which is found be ethylene oligomerisation active and can be easily removed after reaction(polyethylene bound Cr catalyst is soluble at higher temperature but is not soluble at room temperature). The selectivity of the polyethylene bounded Cr(PNP) is still quite high but the activity of the catalyst has dropped as expected. In this case, this type of end-functionalized material can provide a pathway for heterogenizing homogeneous catalysts.
References 1. M. Meurs, G. Britovsek, V. Gibson and S. Cohen, J. Am. Chem. Soc. , 2005, 213 , 9913-9923.
2. D. Damiron, J. Mazzolini, D. Cousin, C. Bossion, F. D'Agosto and E. Drockenmuller, Polym. Chem. , 2012, 3 , 1838-1845. 3. A. Bollmannm, K. Blannm, J. T. Dixon, F. M. Hess, E. Killian, H. Maumela, D. S. McGuiness, D. H. Morgan, A, Neverling, S. Otto, M.Overett, A. Slawin, P. Wasserscheid, and S. Kuhlmann, J. Am. Chem. Soc. , 2004, 126 , 14712-14713.
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