Kinetics of anionic polymerization of o-methylstyrene in 2-methyltetrahydrofuran and tetrahydrofuran

Abstract

The kinetics of anionic polymerization of o-methylstyrene were investigated in 2-methyltetrahydrofuran (MTHF) at 25°C with Li+, Na+, K+ and Cs+ as gegenions in the presence and absence of an electric field. Conductance studies showed that the dissociation constants K vary remarkably with the gegenion and that the lithium and sodium salts are dissociated to larger extents than the respective polystyryl salts. The free ion rate constant k$ was -2 X lo4 M-' s-which was smaller than that of polystyrene. From the conductivity data, the field effect was concluded to be due to an increase in k i with increase of the field strength as in other systems. The k i reached a limiting value of w3 x lo4 M-l s-' above 3 kVlcm. The ion pair rate constants kb were 2, 1, 16 and 30 M-' s-l for Li+, Na+, K+ and CS+, respectively. Comparison with polystyrene systems led to the conclusion that the behaviour of poly(o-methylstyryl) salts are due to steric hindrance effects of the methyl group in the ortho position. The field-accelerating effects reflected in the k i term as in other systems are smaller than that of poIystyrene systems. This is discussed in terms of the ortho effect. The kinetics of the caesium salt of poly(o-methylstyrene) were also studied in tetrahydrofuran (THF) at 25°C. The results are compared with those in MTHF.* This article is part 19 of Ionic Polymerization under an Electric Field.

Effect of the Substituent Position on the Anionic Copolymerization of Styrene Derivatives: Experimental Results and Density Functional Theory Calculations

“…In nonpolar solvents such as cyclohexane or benzene, isoprene is incorporated preferably, while in polar solvents such as tetrahydrofuran (THF), the monomer order is reversed, and styrene is incorporated first. Nevertheless, both polymerizations result in a strong gradient, affording so-called “tapered” block copolymers. , The polymerization kinetics of styrene and its ring-methylated derivatives have hardly been studied, and advanced techniques were not available at the time the few studies were conducted. − …”

On the growing active centers and their reactivities in “living” anionic polymerizations of styrene and its derivatives

“…First, we confine ourselves to ortho-substituted derivatives. It was found (22,40) that o-methylstyrene (o-MS) has smaller k6 and k; and larger K than styrene, mand p -methylstyrtme (m-MS and p-MS). It is reasonable that the reactivity of monomers is lowered by methyl group, since this is electron-donating.…”