Effects of Ether on the Cationic Polymerization of Isobutylene Catalyzed by AlCl₃

Abstract

In this work, we prepared different initiator solutions containing ether and AlCl 3 by changing the addition sequence of ingredients, studied the interactions between ether and AlCl 3 from the evolution of the Fourier transform infrared (FTIR) spectra by comparison, and investigated the catalytic performances of AlCl 3 affected by ether for isobutylene polymerization. We observed that different preparation methods of initiator solutions could lead to two kinds of interactions between ether and H 2 O/AlCl 3 in hexane. The strong interaction could stabilize carbenium ions and seriously decrease the catalytic performance, whereas the weak interaction could promote isomerization and proton elimination. Moreover, we found that the preparation method of initiator solutions was not a critical factor in CH 2 Cl 2 . Finally, a universal mechanism based on the AlCl 3 -involved interactions in different solvents was proposed to understand the effects of ether on the cationic polymerization catalyzed by AlCl 3 thoroughly.

Characteristics and Mechanism of Vinyl Ether Cationic Polymerization in Aqueous Media Initiated by Alcohol/B(C6F5)3/Et2O

“…The reaction between B(C 6 F 5 ) 3 and Et 2 O were investigated with ATR-FTIR spectroscopy, as shown in Figure 1. When Et 2 O comes in direct contact with B(C 6 F 5 ) 3 , the absorbance at 1091 and 774 cm -1 is changed, which indicates the interaction between B(C 6 F 5 ) 3 and Et 2 O [42,43,44]. The B(C 6 F 5 ) 3 /Et 2 O complex can react with H 2 O or alcohols to form an active species, which can initiate polymerization (Table 1).…”

Statistical kinetic modeling procedure for cationic polymerization and its application to polyisobutylene

“…Also, the resulting molecular weight distribution can be affected by system conditions and the solvent type. It is known that the distribution narrows when a polar solvent is used and broadens with a non‐polar solvent 16,24,25 . Based on the quasi‐living mechanism, this difference is explained by how the cations exist between the ion‐pair and the unpaired ion (free ion) states in the solvent 6,17 (Figure 3).…”

“…The proposed modeling procedure is demonstrated on polyisobutylene (PIB), which is by far the most common industrial application of cationic polymerization. PIB uses isobutylene as the monomer, and the molecular weight varies from thousands to hundreds of thousands depending on the type of commercial product 4,16‐18,22‐29 . PIB is a non‐toxic polymer with desirable characteristics such as high stability and adhesion, and decomposes without residue at high temperature.…”

“…It is known that the distribution narrows when a polar solvent is used and broadens with a non-polar solvent. 16,24,25 Based on the quasi-living mechanism, this difference is explained by how the cations exist between the ion-pair and the unpaired ion (free ion) states in the solvent 6,17 (Figure 3). However, there is a lack of studies that describe the transition between these states in the context of reaction kinetics.…”

Tailoring the AlCl3/iPr2O/Et2O initiation system for highly reactive polyisobutylene synthesis in pure n-hexane

“…Our previous investigations have shown that introducing nucleophilic reagents into the initiator solution is an effective and direct method to adjust the active centers and chain reactions when using AlCl 3 as a coinitiator. [29][30][31] In detail, strongly basic Et 2 O can decrease the acidity of AlCl 3 via complexation and inhibit its catalysis of H 2 O dissociation, which can stabilize carbenium ions and decrease the polymerization rate in CH 2 Cl 2 /n-hexane solvent mixtures. Meanwhile, the free Et 2 O signicantly promotes proton elimination and isomerization, resulting in a high conversion rate and a low content of exo-olen.…”