Solvent effect in polymerization of isoprene initiated by tropylium and trityl salts

Gaylord, Norman G.; Švestka, M.

doi:10.1002/pol.1969.110070608

Cited by 6 publications

(17 citation statements)

References 11 publications

(2 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This observation provides evidence that both initiation and propagation proceed via allylic carbocations in the cationic polymerization of IP. Similar polyisoprene structures were also obtained with different initiating systems such as BF 3 ,6, 7 SnCl 4 ,6, 7 AlCl 3 ,6, 7 AlEtCl 2 ,8 SnCl 4 /CCl 3 COOH,9 TiCl 4 /CCl 3 COOH or CF 3 COOH,10–14 and 1‐(4‐methoxyphenyl)ethanol/B(C 6 F 5 ) 3 15…”

Section: Introductionsupporting

confidence: 71%

Homogeneous polymerization of ethylene using an iron‐based metal catalyst system

Mahdavi

Badiei

Zohuri

et al. 2006

J of Applied Polymer Sci

View full text Add to dashboard Cite

The polymerization of isoprene initiated by dimethylallyl alcohols (DMAOH) in the presence of Lewis acids (LAs) as coinitiators has been selected as a potential model of the proposed cationic mechanisms involved in natural rubber (NR) biosynthesis. In view to investigate the activation/ionization mechanism of the allyl alcohol chain terminus (PIAllOH), which was shown to exist in NR, different isomers of DMAOH were used as simple models of polyisoprene chain‐end structures in the presence of tris(pentafluorophenyl)borane (BLA) as a LA. It is shown that cationation of 3,3‐DMAOH by BLA proceeds by direct OH abstraction. However, this process is strongly retarded in the presence of 2,6‐di‐tert‐butylpyridine (dtBP), due to the formation of different BLA complexes, one with 3,3‐DMAOH, active for cationation, and a dormant one involving its ionized form 3,3‐DMAO−. The monomer generated in situ by ionization/proton elimination steps subsequently adds on the primary allylic carbocation form, then resulting in the formation of oligoisoprenes, whereas the tertiary carbocation form of the allylic carbocation yields exclusively to proton elimination and isoprene formation, a possible mechanism of chain‐end termination. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.

show abstract

Section: Introductionsupporting

confidence: 71%

Homogeneous polymerization of ethylene using an iron‐based metal catalyst system

Mahdavi

Badiei

Zohuri

et al. 2006

J of Applied Polymer Sci

View full text Add to dashboard Cite

show abstract

“…When the electron-donor monomer is a strong donor such as styrene or butadiene, interaction with the metal halide-complexed electron-acceptor monomer, which has become a stronger acceptor as a result of complexation, results in the formation of a charge-transfer complex which undergoes spontaneous or radical-initiated homopolymerization to yield equimolar, alternating copolymers, irrespective of the initial monomer composition (46)(47)(48)(49).…”

Section: R-cfmentioning

confidence: 99%

“…Equimolar, alternating copolymers are produced, independent of monomer charge, when butadiene or isoprene are copolymerized with acrylonitrile in the presence of zinc chloride and in the absence as well as in the presence of a peroxide catalyst (45,47,52). The alternating copolymer is accompanied by polyacrylonitrile when the reaction is carried out at elevated temperatures or to high conversions when the acrylonitrile is present in great excess or the ZnCI,/AN molar ratio is high.…”

Section: R-cfmentioning

confidence: 99%

“…Butadiene and isoprene (45,47) as well as vinyl chloride (58) also copolymerize with acrylonitrile in the presence of ethylaluminum halides to yield alternating copolymers. As in the case of the zinc chloride-activated polymerizations, the butadiene-acrylonitrile alternating copolymers produced in the presence of the ethylaluminum halides, essentially independent of monomer charge, have trans-l,4 unsaturation (45,47,52).…”

Section: R-cfmentioning

confidence: 99%

See 1 more Smart Citation

Donor‐acceptor complexes in copolymerization. VI. A proposed mechanism for the homopolymerization of comonomer complexes to alternating copolymers

Gaylord

1970

J. polym. sci., C Polym. symp.

Self Cite

View full text Add to dashboard Cite

SYNOPSISAfter a brief review of the characteristics of the copolymerization of donor and acceptor monomers in the presence of metal halides, a mechanism is proposed for the formation of alternating copolymers. The charge-transfer donor-acceptor complex resulting from the interaction of a strong electronacceptor monomer and a strong electrondonor monomer undergoes spontaneous or radical initiated homopolymerization to yield an equimolar alternating copolymer, irrespective of the initial monomer ratio. The formation of the [ D t r A ] complex is enhanced by complexation of the acceptor monomer with a metal halide or organometal halide. The homopolymerization of the ( D k A ... MX] occurs at a faster rate than conventional radical copolymerization. The spontaneous polymerization occurs when the equilibrium concentration of the complex is sufficiently high. The latter depends upon the electrondonating strength of the donor monomer and the electronaccepting strength of the acceptor monomer and the activator. Complex formation is favored at lower temperatures while polymerization may require thermal or catalytic activation. The complexes may be aligned in an ordered array or matrix, and polymerization proceeds through a rapid initial stage in which the molecular weight increases with conversion, followed by a slower stage in which the molecular weight remains constant a t the highest level attained in the first stage, indicative of the first-stage polymer acting as a template for the secondstage polymerization. The proposed polymerization mechanism involves initiation by a head-to-head reaction of two complexes during which hydrogen abstraction or transfer occurs through a six-membered cyclic transition state to generate a polymer chain with an attached terminal complex. The propagation reaction is head-to-tail and involves the addition of complexes to the chain end through hydrogen abstraction via a six-membered cyclic transition state to regenerate the complex chain end.

show abstract

“…The structure is presumed t o be derived from 1,2-polybutadiene by cyclization and isomerization reactions. (94) The polymerization of isporene with Lewis acids in nitrobenzene in the absence of water or other detectable co-catalyst results in the formation of polyisoprene containing cyclic units as well as linear unsaturation (99). Whereas antimony pentachloride, arsenic pentachloride, titanium tetrachloride, and phosphorus pentafluoride initiate the cyclopolymerization of isoprene in nitrobenzene, no catalytic -IT-…”

Section: Xx>; > -(93)mentioning

confidence: 99%

Solvent effect in polymerization of isoprene initiated by tropylium and trityl salts

Cited by 6 publications

References 11 publications

Homogeneous polymerization of ethylene using an iron‐based metal catalyst system

Homogeneous polymerization of ethylene using an iron‐based metal catalyst system

Donor‐acceptor complexes in copolymerization. VI. A proposed mechanism for the homopolymerization of comonomer complexes to alternating copolymers

One‐electron transfer initiated polymerization reactions I. Initiation through monomer cation radicals

Contact Info

Product

Resources

About