No 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

The controlled cationic polymerization of styrene using CumOH/AlCl 3 OBu 2 /Py initiating system in a mixture CH 2 Cl 2 /n-hexane 60/40 v/v at À40 and À60 C is reported. The number-average molecular weights of the obtained polystyrenes increased with increasing monomer conversion (up to M n ¼ 85,000 g mol À1 ) although experimental values of M n were higher than the theoretical ones at the beginning of the reaction that was ascribed to slow exchange between reversible-terminated and propagating species. The molecular weight distribution became narrower through the reaction and leveled of at the value of M w /M n ¼ 1.8-2.0. A kinetic investigation revealed that the rate of polymerization was first-order in AlCl 3 OBu 2 concentration meaning that monomeric counteranion (AlCl 3 OH À or AlCl À 4 ) involved in the initiation and propagation steps of the reaction. It was also found that the rate of polymerization decreased with lowering temperature, which could be attributed to a decrease in concentration of free Lewis acid (AlCl 3 ), the true coinitiator of polymerization, because of an increase in the tightness of its complex with dibutyl ether.

No abstract

No abstract