Participation of the depropagation reaction in the cationic copolymerization of 3.3‐bischloromethyl oxacyclobutane and tetrahydrofuran

Yamashita, Yuya; Kasahara, Hirotaka; Suyama, Katsuhiko; Okada, Masahiko

doi:10.1002/macp.1968.021170123

Cited by 20 publications

(2 citation statements)

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“…The first step in the characterization of MAO is the determination of the TMA content. The addition of increasing quantities of tetrahydrofuran (THF, pK b = 5) 37 to MAO (30% solution in toluene) was studied by 1 H NMR spectroscopy (Figure 1). THF cleaves Al 2 Me 6 to give AlMe 3 •THF, with a signal shift to higher field (ca.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Probing the Structure of Methylalumoxane (MAO) by a Combined Chemical, Spectroscopic, Neutron Scattering, and Computational Approach

et al. 2013

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The composition of methylalumoxane (MAO) and its interaction with trimethylaluminum (TMA) have been investigated by a combination of chemical, spectroscopic, neutron scattering, and computational methods. The interactions of MAO with donor molecules such as THF, pyridine, and PPh 3 as a means of quantifying the content of "free" and "bound" TMA have been evaluated, as well as the ability of MAO to produce [Me 2 AlL 2 ] + cations, a measure of the electrophilic component likely to be involved in the activation of single-site catalysts. THF, pyridine, and diphenylphosphinopropane (dppp) give the corresponding TMA−donor ligand complexes accompanied by the formation of [Me 2 AlL 2 ] + cations. The results suggest that MAO contains not only Lewis acid sites but also structures capable of acting as sources of [AlMe 2 ] + cations. Another unique, but still unresolved, structural aspect of MAO is the nature of "bound" and "free" TMA. The addition of the donors OPPh 3 , PMe 3 , and PCy 3 leads to the precipitation of polymeric MAO and shows that about one-fourth of the total TMA content is bound to the MAO polymers. This conclusion was independently confirmed by pulsed field gradient spin echo (PFG-SE) NMR measurements, which show fast and slow diffusion processes resulting from free and MAO-bound TMA, respectively. The hydrodynamic radius R h of polymeric MAO in toluene solutions was found to be 12 ± 0.3 Å, leading to an estimate for the average size of MAO polymers of about 50−60 Al atoms. Small-angle neutron scattering (SANS) resulted in the radius R S = 12.0 ± 0.3 Å for the MAO polymer, in excellent agreement with PFG-SE NMR experiments, a molecular weight of 1800 ± 100, and about 30 Al atoms per MAO polymer. The MAO structures capable of releasing [AlMe 2 ] + on reaction with a base were studied by quantum chemical calculations on the MAO models (OAlMe) n (TMA) m for up to n = 8 and m = 5. Both −O−AlMe 2 −O− and −O−AlMe 2 −μ-Me− four-membered rings are about equally likely to lead to dissociation of [AlMe 2 ] + cations. The resulting MAO anions rearrange, with structures containing separated Al 2 O 2 4-rings being particularly favorable. The results support the notion that catalyst activation by MAO can occur by both Lewis acidic cluster sites and [AlMe 2 ] + cation formation.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Probing the Structure of Methylalumoxane (MAO) by a Combined Chemical, Spectroscopic, Neutron Scattering, and Computational Approach

et al. 2013

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“…Introduction. Copolymerization of a given monomer, after it has reached equilibrium with its homopolymer, is a well-known general phenomenon and was studied in the past by several authors. − The monomer in equilibrium may interact either stronger or weaker with a foreign active center than with its own. In the former instance its equilibrium monomer concentration ([M] eq ) would decrease, whereas in the latter no effect on [M] eq would be observed.…”

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Copolymerization of ll-Lactide at Its Living Polymer−Monomer Equilibrium with ε-Caprolactone as Comonomer

et al. 2005

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Polyethers, Tetrahydrofuran and Oxetane Polymers

Pruckmayr

Dreyfuss²,

Dreyfuss³

2000

Kirk-Othmer Encyclopedia of Chemical Technology

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This article reviews tetrahydrofuran and oxetane polymers and polymerization. The physical and chemical properties of polytetrahydrofurans and polyoxetanes are discussed, as well as the polymerization mechanism, including initiation, propagation, termination, chain transfer, kinetics, and copolymerization to give block, graft, and star copolymers. The most important commercial product is poly(tetramethylene ether) glycol (PTMEG), sold under the trade names Terathane (Du Pont), PolyTHF (BASF), and Polymeg (QO Chemicals). The manufacture of PTMEG is described in some detail, including the most recent industrial processes. Storage and handling of PTMEG, as well as specifications and standards of commercial products, are given. Test methods used in the 1990s are referenced, such as hydroxyl number, polymer molecular weight, and molecular weight distribution. Health and safety factors are discussed, as well as the economic aspects of PTMEG production. Most important uses of PTMEG are in elastomeric polyurethanes and polyesters. The same type of information is given for oxetane polymers, although no oxetane polymer has found any practical application and is thus not available commercially as of 1995.

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Participation of the depropagation reaction in the cationic copolymerization of 3.3‐bischloromethyl oxacyclobutane and tetrahydrofuran

Cited by 20 publications

References 21 publications

Probing the Structure of Methylalumoxane (MAO) by a Combined Chemical, Spectroscopic, Neutron Scattering, and Computational Approach

Probing the Structure of Methylalumoxane (MAO) by a Combined Chemical, Spectroscopic, Neutron Scattering, and Computational Approach

Copolymerization of ll-Lactide at Its Living Polymer−Monomer Equilibrium with ε-Caprolactone as Comonomer

Polyethers, Tetrahydrofuran and Oxetane Polymers

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