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RESEARCH PRODUCT

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A newly designed automatically controlled stirred reactor suitable for kinetic measurements of reactions with half lives ≥2s has been applied to follow the anionic polymerization of methyl methacrylate in THF with Na+ as a counter ion in the presence of an excess of NaB(C6H5)4. As initiators were used: benzylsodium reacted with α-methylstyrene (I), fluorenylsodium (II), and 9-methylfluorenylsodium (III). With I the initiation is fast as compared with the polymerization reaction which is first order in monomer concentration. Within the range of −50°C to −100°C an almost unperturbed “living” polymerization is observed. The Arrhenius plot of the rate constants results in a straight line with activation energy Ea = 4,4kcal·mol−1 (= 18kJ·mol−1) and frequency exponent A = 7,0.II and III are slow initiators, II giving rise to side reactions because of the “acidic” proton in 9-position after initiation, III exhibiting a rate constant of initiation ki = 1l·mol−1·s−1 at −72°C. The termination reaction is becoming increasingly important with increasing temperature and seems to be a unimolecular reaction with Ea,t = 11,5kcal·mol−1 (= 48 kJ·mol−1) and At = 10. Since the basic feature of the reactor is the possibility of drawing samples, polymers from each state of the reaction were available to be investigated also with respect to their tacticity. The monomer addition was shown to follow Bernoullian statistics. A structure of the “living” end being in harmony with the results observed is discussed.