Some aspects of initiation and molecular weight distribution in the anionic polymerization of styrene

Abstract

The initiation of styrene polymerization with n‐butyllithium in toluene was investigated spectrophotometrically. The rate of the first step of initiation is first order in both monomer and catalyst, and the activation energy is 26.3 kJ · mol−1. The kinetic analysis revealed a number of kinetic transitions attributed to the formation of secondary aggregates from reacted and unreacted n‐C4H9Li. The molecular weight distribution narrows with increasing reaction temperature, indicating the activation energy of the last step of initiation to be higher than that of propagation.

Anionic polymerization of styrene. Effect of aromatic ethers

“…A similar result was previously obtained for styrene initiation with n-butyllithium in aromatic solvents in the absence of Lewis bases[4].Earlier investigations [4] have shown that styrene initiation with n-butyllithium is a rather complicated process, occurring through the intermediate of secondary (mixed) aggregates of increasing size and decreasing reactivity towards t h e monomer. A similar result was previously obtained for styrene initiation with n-butyllithium in aromatic solvents in the absence of Lewis bases[4].Earlier investigations [4] have shown that styrene initiation with n-butyllithium is a rather complicated process, occurring through the intermediate of secondary (mixed) aggregates of increasing size and decreasing reactivity towards t h e monomer.…”

“…Anisole (Carlo Erba) and diphenyl ether (E. Merck) were purified by repeated washing with sodium hydroxide solution, distillation in vacuum on a high efficiency column packed with nickel helices and were subsequently dried over calcium hydride. the catalyst conversions a t which changes in slope occur, are virtually the same as in the case of polymerizations carried out in the absence of Lewis bases [4]. It can be seen that, for both ki,l and rate constants corresponding to catalyst conversions in the ranges 0.4...0.5, 0.5-..0.6, 0.67...0. 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 , since the linearity of the segments demonstrates that the process is first-order in catalyst throughout the initiation process.…”

“…(Figures 7 and 8). However, the scattering around the central values given in Table 2 of Ref, [4] was somewhat higher and in certain runs some of the kinetic transitions could not be identified. The position of the kinetic transition points, i.e.…”

“…Initiation was followed spectrophotometrically a t 445 nm [4]. Initiation was followed spectrophotometrically a t 445 nm [4].…”

“…Initiation was followed spectrophotometrically a t 445 nm [4]. A t the end of each run, the actual concentration of active centers was determined by titration with n-butanol [4]. A t the end of each run, the actual concentration of active centers was determined by titration with n-butanol [4].…”