Kinetic studies of the anionic polymerization of methyl methacrylate in tetrahydrofuran with Na⁺ as counter ion, using monofunctional initiators

Abstract

A newly designed automatically controlled stirred reactor suitable for kinetic measurements of reactions with half lives 2 2 s 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),.As initiators were used: benzylsodium reacted with a-methylstyrene (I), fluorenylsodium (II), and 9-methylfluorenylsodium (111). 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 astraightlinewithactivationenergyE,=4,4kcal.mol-' (= 18 kJ.mol-')andfrequencyexponent A=7,0. I1 and 111 are slow initiators, I1 giving rise to side reactions because of the "acidic" proton in 9-position after initiation, 111 exhibiting a rate constant of initiation k, = 11 .mol-' .s-' at -72°C. The termination reaction is becoming increasingly important with increasing temperature and seems to be a unimolecular reaction with Ea,, = 11,5 kcal . mol' (=48 kJ . mol-I ) and A, = 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. *) Performed at the "Institut fur Makromolekulare Chemie, Universitat Freiburg". The courtesy of Prof. Cantow is greatly acknowledged.

The effect of TMEDA on the kinetics of the anionic polymerization of methyl methacrylate in tetrahydrofuran using lithium as counterion

“…The activation energy calculated from the combined data points obtained in the absence and presence of TMEDA is found to be E a,t = 35 5 kJ N mol -1 and the frequency exponent, log A t = 6.7 l 0.9. These values are lower than the ones reported for MMA polymerization with Na + counterion in THF [43] (E a,t = 48 kJ N mol -1 and A t = 10), confirming the earlier observation that termination is less significant for larger counterions. [1][2][3] …”

Poly(ammonium alkoxydicyanoethenolates) as new hydrophobic and highly dipolar poly(zwitterions). 2. Mechanistic aspects of the polymerization

“…These characteristic features may be ascribed to slow initiation with respect to fast propagation, as already noticed for MMA in THF solution. [35][36][37][38] The sharp tacticity contrast between PMMA and the poly(zwitterion) obtained under similar conditions (DMF, Li+, -40 "C) is especially striking and requires further discussion (see Table VIII). PMMA is predominantly syndiotactic and shows here again only weak deviations from the two stereopropagation mechanisms ( P ( m / r ) = 0.833 and P ( r / m ) = 0.147).…”

A statistical analysis for stereo‐configurational sequences of vinyl polymers

“…Under the condition of steady state, Eqs. (14) and (23) hold regardless of the order of Markovian process, thus we can regard Eqs. (14) and (23) as the decision equations of the stationary stage reaction.…”

“…(14) and (23) hold regardless of the order of Markovian process, thus we can regard Eqs. (14) and (23) as the decision equations of the stationary stage reaction. In literature, little attention has been paid to the constraint condition with which the decision equations of various Markovian processes hold.…”