Metalloester, 9. Untersuchung des anfangsstadiums der anionischen polymerisation von methylmethacrylat. Reaktion von methyl‐2‐sodioisobutyrat mit methylmethacrylat

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Abstract
In the reaction of methyl methacrylate (2) with methyl 2‐sodioisobutrate (1) (a model of the active center in the anionic polymerization of 2) in a mole ratio of 2:1, the concentrations of all known initial compounds and reaction products were estimated. This reaction was studied in a flow reactor with reaction times between 0,02 and 1,4 s using GLC, LC and GPC as analytical methods. At the same time, a rise in temperature of the reaction mixture by 6°C was observed (for [2] = 0,2 mol/1); at a higher concentration of 2 (0,6 mol/1), this rise was 27°C and hence not negligible in the interpretation of the results. The concentration changes of the individual products were in accordance with the concept of a stepwise addition of 2, to the metalloesters. At the end of the reaction the mean molecular weight of the addition products corresponded roughly to the ratio 2/effective 1. The cyclization of Na‐trimer 4a to a cyclic trimer 9 was shown to be an important side reaction. The Na‐tetramer 5a and the higher Na‐oligomers 6a probably undergo a similar cyclization. 2 added 1 very quickly; the following approximate order of reaction rates (Scheme 1) is proposed: R1 > R2, R3, R4, … > Rc.

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