Kinetic study on the living/controlled cationic polymerization of p‐methoxystyrene coinitiated by tris(pentafluorophenyl)borane

Abstract

A kinetic study of the living cationic polymerization of p-methoxystyrene using 1-(4-methoxyphenyl)ethanol (1)/B(C 6 F 5 ) 3 initiating system in a mixture of CH 3 CN with CH 2 Cl 2 1:1 (v/v) at room temperature was carried out utilizing a wide variety of conditions. The polymerization proceeded in a living fashion even in the presence of a large amount of water ([H 2 O]/[B(C 6 F 5 ) 3 ] ratio up to 20) to afford polymers whose M n increased in direct proportion to monomer conversion with fairly narrow MWDs (M w /M n 1.3). The investigation revealed that the rate of polymerization was first-order in B(C 6 F 5 ) 3 concentration, while a negative order in H 2 O concentration close to À2 was obtained. It was also found that the rate of polymerization decreased with lowering temperature, which could be attributed to a decreased concentration in free Lewis acid, the true coinitiator of polymerization. A mechanistic scheme to explain the kinetic behavior of living p-methoxystyrene polymerization is proposed, which has been validated by PREDICI simulation on multiple-data curves obtained by 1 H NMR in situ polymerization experiment. V V C 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: [6928][6929][6930][6931][6932][6933][6934][6935][6936][6937][6938][6939] 2008

Controlled cationic polymerization of styrene using AlCl3OBu2 as a coinitiator: Toward high molecular weight polystyrenes at elevated temperatures

“…5). This value correlates well with one ( E a,app = 62.4 kJ mol −1 ) reported by us for the polymerization of p‐methoxystyrene using 1‐(4‐methoxyphenyl)ethanol/B(C 6 F 5 ) 3 initiating system in a CH 3 CN/CH 2 Cl 2 mixture 39. A rational explanation for this observation may be found in the increase of tightness of the complex of Lewis acid (AlCl 3 ) with dibutyl ether with decreasing temperature that led to the decrease of the instantaneous concentration of free Lewis acid and, in turn, to the observed decrease in the polymerization rate with the lowering of temperature 39…”

A New Insight into the Mechanism of 1,3‐Dienes Cationic Polymerization III: Polymerization of 1,3‐Pentadiene with CF3COOD/TiCl4 Initiating System: Chain‐Ends Structure and Kinetics

“…On the other hand, the values of k p obtained here are much lower than those for the vinyl monomers of comparable reactivity (substituted styrenes) obtained using diffusion clock methods . Although the validity of the rate constants for propagation obtained by diffusion clock methods is questionable for less reactive monomers such as isobutylene and styrene and its derivatives, a good correlation between the k p values determined using the diffusion clock method ( k p = 11.4 × 10 4 L mol −1 s −1 at –30 °C), from an evaluation of ionic species concentration by spectroscopic methods ( k p = 2.8 × 10 4 L mol −1 s −1 at 0 °C) and those calculated based on PREDICI simulation ( k p = 4.9 × 10 4 L mol −1 s −1 at 20 °C) is observed for more reactive p ‐methoxystyrene. The problem associated with the method proposed here can be an over­estimation of the concentration of active species and, in turn, an underestimation of k p , since the concentration of deuterium (polymer chains) even at very early stages of polymerization can be higher than the real (instantaneous) concentration of the growing species due to the existence of an equilibrium between the propagating and non‐propagating species .…”

Cationic polymerization of isoprene using zinc halides as co‐initiators: towards well‐defined oligo(isoprene)s under mild conditions

“…The observed decrease of the polymerization rate with decreasing polymerization temperature could be explained by the increase of strength of interaction of Lewis acid (ZnBr 2 ) with diethyl ether with decreasing temperature that leads to a decrease of the instantaneous concentration of free Lewis acid. 37,40 M n and M w of the polyisoprenes obtained increase while MWD becomes broader with a change of polymerization temperature from 60 to −15 • C ( Table 5). Similar dependences of the reaction rate and molecular weight on the temperature are observed for the cationic polymerization of isoprene with CCl 3 COOH/ZnCl 2 (supporting information, Table S3) and CCl 3 COOH/ZnI 2 (Table 6) initiating systems.…”