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

Abstract

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.

Synthesis of hydrocarbon polymers by cationic polymerization and their thermal properties

“…As shown in Figure 1(a), the 13 C NMR spectrum of the CDCl 3 -soluble fraction of poly(Ind-co-ENB) obtained with an ENB feed of 20% features resonances in the region from 145 to 148 ppm, which were assigned to the ethylidene double bond carbons [23,24]. The chemical shifts due to the aromatic ring carbons can be detected in the region from 123.5 to 127.5 ppm [10,23], while the resonance peaks from 45.0 to 53.0 ppm are due to the cyclic chain methine carbons.…”

“…Due to the high T g and intermediate M n , the obtained PInd produced brittle films; this can be remedied by producing PInd with higher M n or even producing new compounds such as block copolymers with rubbery or polar monomers [20]. 13 C and 1 H NMR spectra, respectively, of the PInd and Ind-copolymers obtained in this study. As expected, two distinct resonances corresponding to the aromatic and aliphatic carbons are evident in the 13 C NMR spectrum of PInd [10,20,21].…”

“…13 C and 1 H NMR spectra, respectively, of the PInd and Ind-copolymers obtained in this study. As expected, two distinct resonances corresponding to the aromatic and aliphatic carbons are evident in the 13 C NMR spectrum of PInd [10,20,21]. The two ring junction carbons (labeled 8 and 9) appear as broad multiple resonances centered at 145.6 and 147 ppm, respectively.…”

“…Polystyrenes (PSs) with an M n of 85 Â 10 3 g/mol and M w /M n of 1.8-2.0 were obtained with CumOH/AlCl 3 OBu 2 /Py at a low temperature [13]. A key factor in achieving living polymerization behavior is the use of an AlCl 3 co-initiator with an appropriate electron donor (e.g.…”

A Catalyst Platform for Unique Cationic (Co)Polymerization in Aqueous Emulsion

“…[23] Moreover,the final molar masses of polystyrenes were significantly higher than those of pMOS (M n = 80-190 kg mol À1 ), whereas MWD was slightly broader (Table 1). [24] This is the highest molar mass ever reported for the cationic polymerization in aqueous media [8] (and even in solution [25] )a ts uch "high" polymerization temperature. Theobserved difference in the polymerization behaviors may be due to the fact that styrene is less polar than pMOS and, therefore,c ontains less water inside the monomer droplets.…”