Studies on mechanism of tetrahydrofuran polymerization initiated by a heteropolyacid

Abstract

SUMMARY: Polymerization mechanism of tetrahydrofuran initiated with H 3 PW 12 O 40 in the presence of ethylene oxide (EO) was studied by means of NMR, GC and GPC. The polymerization stopped after complete consumption of EO, but could be re-initiated when a further portion of EO was added. A part of EO was converted into dioxane in the beginning of polymerization in the presence or absence of water, but the formation of dioxane was suppressed by addition of a low molecular weight diol. All the polymer chains were started with EO moieties, and the percentage of hydroxyl group attached to EO moieties at the polymer chain ends was higher than 50% of the total hydroxyl end groups and increased with conversion. Kinetic experiments were performed with successive addition of EO, indicating that the concentration of propagating species and the chain propagation rate constant remained unchanged during polymerization after each addition of EO. The rate constant of the reaction of EO with the propagating species in EO homopolymerization was determined by GC to be 3.6610The high reactivity of EO offered the possibility of tetrahydrofuran polymerization via dormant dioxanium species. The molecular weight distribution index of the product decreased with conversion, in some runs it was lower than 1.3 at a conversion as high as 46.9%.

Keggin heteropolyacids as catalyst for the polymerization of β-pinene

“…12 showed the best catalytic performance among the catalysts tested. Untreated PW 12 has no catalytic activity.…”

“…Such catalysts offer many advantages compared to their counterparts: milder reaction conditions, no need for solvents or the use of less toxic ones, easier separation of the catalyst from the reaction mixture by filtration. For example, Afang Zhang et al have used HPA to carry out highly controlled polymerization of tetrahydrofuran, thus obtaining high molecular weight production [12]. Valérie Sage and co-workers have published supported copper triflate as catalyst for the cationic polymerization of styrene [13].…”

Preparation of Polyether Triol and Three-Armed Polyether Triol by Tetrahydrofuran Polymerization Initiated with Heteropolyacid

“…Each consumption of one hydroxyl group of TMP moieties in the transfer reaction resulted in formation of an oxyethylene hydroxyl end-group. The proton produced by chain transfer reaction would initiate oxirane with PW 12 to form a new propagating chain, which also started with oxyethylene hydroxyl group [19] as shown by reaction 1 in Scheme 1.…”

“…Each consumption of one hydroxyl group of TMP moieties in the transfer reaction resulted in formation of an oxyethylene hydroxyl end-group. The proton produced by chain transfer reaction would initiate oxirane with PW 12 to form a new propagating chain, which also started with oxyethylene hydroxyl group [19] as shown by reaction 1 in Scheme 1.When water or NaOH was added to terminate the propagating chains that still have not transferred to hydroxyl groups, the polyether diol chains might be formed. In order to evade or reduce the formation of polyether diols the catalyst phase was isolated before the termination reaction so that the cationic propagating chains could be isolated in company with the anions of PW 12 .…”

β-Pinene cationic polymerization using Keggin heteropolyacid catalysts

“…In these reactions, the aimed catalysts acted as polymerization initiators, and the reaction mechanism was accepted commonly as cationic polymerization [13][14][15][16][17][18][19]. Burrington et al [20] have published on the use of a heteropolyacid salt as catalyst for the cationic polymerization of isobutylene.…”