Effect of the nature of the alkyl group of initiation and termination in R(3)Al/RLi initiation of methyl methacrylate

The polymerisation of methyl methacrylate has been investigated with mixed aluminium and lithium alkyls. The use of sterically hindered aluminium alkyls such as triisobutyl aluminium in conjunction with tert-butyl lithium leads to living polymerisation at 0 degrees C with little complications from secondary initiation or premature termination. The use of less bulky alkyl groups on either aluminium or lithium leads to both secondary initiation, as observed by the formation of high molecular weight polymer by GPC-LALLS and termination via cyclisation as observed by MALDI-TOF-MS. The initiator efficiencies, even when living polymerisation ensues, are considerably less than 100%