The Electronic Spectra of Some Anionic Polymerization Systems

Bywater, S.; Johnson, A. F.; Worsfold, D. J.

doi:10.1139/v64-197

Cited by 87 publications

(17 citation statements)

References 11 publications

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“…Tobolsky has, however, reported before that little change in microstructure occurred after the abrupt change caused by the first sinall addition of tetrahydrofuran. The smoother change above is more in accord with the finding from ultraviolet studies of the polyisoprenyl carbanion forined in these systems (20). There appears to be very little change in the ionic nature of the carbon metal bond a s the solvent and the alkali metal are changed, and little reason to expect abrupt changes in microstructure.…”

Section: Polymer Microstrzlctzlresupporting

confidence: 75%

Anionic Polymerization of Isoprene

Worsfold¹,

Bywater²

1964

Can. J. Chem.

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184

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The polymerization of isoprene with butyllithium in cyclohexane has been studied. The initiation reaction was found to be complex; plots of conversion of butyllithium against time are sigmoidal. The order with respect to the initiator was found to be between one-half and one. The order of the isolated propagation reaction in polyisoprenyllithium was found to be one-qnarter and was correlated with a fourfold association of active chain ends determined by dilute solution light-scattering measurements.The major effect of tetrahydrofuran on the reaction was the great increase of the initiation rate. The kinetic order changes slowly with the addition of small amounts of tetrahydrofuran, suggesting that the aggregates are brolcen down with difficulty. The nlicrostructure of the polymer has been determined by n.m.r. measl~rements and shows a steady transition from a largely 1:4 t o a largely 3:4 s t r u c t~~r e as the polarity of the solvent is increased by the addition of tetrahydrofuran.Very little attention has been paid to the initiation reaction in the polymerization of isoprene by n-butyllithium. Most studies of this system have been concerned with the structure of the polymer formed (1, 2) or with the kinetics of the propagation reaction (3, 4, 5 ) and the effect on both of additives. The reaction of n-butyllithium with both styrene (6) and 1,l-diphenylethylene (7) has been investigated in aromatic hydrocarbon solvents. I t is found that when the solvent is cyclohexane, the kinetic behavior is considerably different for isoprene and also for styrene and butadiene (8).The several published investigations of the propagation reaction have mostly aclmowledged the difficulty of ascertaining whether the slow initiation reaction has gone to completion. By use of spectrophotoinetric measurements it is possible to determine more certainly when chain initiation is complete and hence to ensure that a true propagation rate can be measured. I t is possible, also, to see the effect of only partial initiation on the propagation rate.The microstructure of polyisoprene has been investigated, in the past, by infrared spectroscopy (9, 10) but the method is not always satisfactory, especially with anionic polymers. I t is now possible to determine these structures by nuclear magnetic resonance n.m.r. (11) and, although this method still has some shortcon~ings, it supplenlents the infrared method. From these measurements, it seems necessary to modify previous ideas on these structures.The methods used to measure the reaction rates of n-butyllithium with isoprene were similar t o those used in the past for other systems (6). The absorption band of polyisoprenyllithium in cyclohesane has a maximum a t 270 mp, e 6 900, but to measure its concentration a wavelength of 275 mp was used to avoid as far as possible the absorption of isoprene. Beers law was tested over the range 10-c10-2 ilf, the results showed a random scatter of f 5%. The isoprene concentration was measured a t suitable lower wavelengths.Cyclohexane was clarified ...

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Section: Polymer Microstrzlctzlresupporting

confidence: 75%

Anionic Polymerization of Isoprene

Worsfold¹,

Bywater²

1964

Can. J. Chem.

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184

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“…This reaction has been noted previously with perchloric acid catalysis (6). Hence, very soon after the start of the reaction, the uv spectrum of the diphenylcarbenium ion is replaced slowly by that of the triphenylcarbenium ion.…”

Section: Resultssupporting

confidence: 71%

The reaction of diphenylethylenes with boron trifluoride and water

Bywater¹,

Worsfold²

1977

Can. J. Chem.

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The concentrations have been measured of carbenium ions formed when diphenylethylene and diphenylpropene react with boron trifluoride and water in methylene chloride solution. With both these olefins it appeared necessary that two boron trifluoride molecules should be present for every water molecule to form the carbenium ion. Also the ionic species formed showed a very high degree of ionic dissociation. Diphenylethylene rapidly formed the cyclized dimer, and as a side reaction formed some triphenylmethylcarbenium ions. The diphenylpropene gave a diphenylcarbenium ion that appeared stable, but the accompanying anion was thought to be unstable and rearranged to a more stable form which disrupted the dependences on the concentrations of original reactants.STAXLEY BYWATER et DENIS J. WORSFOLD. Can. J. Chem. 55, 85 (1977) On a mesure les concentrations d'ions carbenium qui sont form& lorsque le diphCnplethylene et le diphenylpropene reagissent avec le trifluorure de bore et l'eau en solution dans le chlorure de methylene. Avec ces deux olefines, il semble necessaire que deux molecules de trifluorure de bore soient prtsentes pour chaque molecule d'eau si l'on veut former un ion carbdnium. De plus les especes ioniques formees presentent un tres haut degre de dissociation ionique. Le diphCnylCthylene forme rapidement un dimere cyclique et une reaction secondaire forme aussi des ions triphCnylmCthylcarbCnium. Le diphenylpropene conduit a I'ion diphenylcarbenium qui semble stable mais il nous est apparu que I'anion qui l'accompagne est instable et qu'il se rearrange pour donner une forme plus stable; ce rearrangement brise la dependance sur les concentrations des rCactifs originaux.[Traduit par le journal] 1,l-Diphenylethylene (DPE) has been used by several authors in model systems of cationic polymerization. Its basic reactions in these systems parallel those found with other monomers, but with the simplifying factor that only a reversible dimerization occurs. Evans et al. (1-3) studied principally the kinetics of these systems in benzene, whereas Sigwalt and co-workers (4, 5) took advantage of the relatively high concentrations of the diphenylcarbenium ion formed in methylene chloride solution to make a spectroscopic study of the active centres. The uv spectra obtained at low temperatures were complex, and three forms of active centre were suggested.An attempt has been made here to use this system to describe the behaviour of boron trifluoride and water as a catalyst-cocatalyst system in the initiation reaction of cationic polymerizations of olefins by spectroscopic measurements of the carbenium ion concentration. Because of the activity of this catalyst, however, the subsequent cyclization reaction found for this monomer complicates the system. Some work has also been done using 1,l-diphenylpropene (DPP) for which the reaction goes no further than the initiation reaction, subsequent dimerization or cyclization is negligible. ExperimentalAll reactions were done in all-glass appartus, with break seals separating react...

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“…Because of the large extinction coefficient of poly(styryl)lithium ( ε = 1.3 × 10 4 L · mol −1 · cm −1 ) at λ max of 334 nm in benzene,37 the reaction was run under dilute conditions (e.g., 2.4 mL of styrene in 700 mL of toluene, and 0.55 mmol of sec ‐BuLi) in order to keep the absorbance below 1. Bywater et al37 reported that the maximum absorbance of the poly(styryl)lithium chain end is not highly dependent on the solvent. Therefore, it was expected that the maximum absorbance in toluene would be near the value reported for benzene.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Diene‐Functionalized Macromonomers via Functionalization with Hexa‐1,3,5‐triene

Quirk

Gomochak

Bhatia

et al. 2003

Macro Chemistry & Physics

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The reaction of poly(styryl)lithium (PSLi) with hexa‐1,3,5‐triene (HXT) was studied as a route to diene‐functionalized macromonomers. When PSLi was reacted with 1.5 molar equivalents of HXT for 2.5 h at −10 °C in toluene, it was found that the diene‐functionalized macromonomer was obtained in high yield; however, oligomerization of the HXT was observed by matrix‐assisted laser absorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). Oligomerization was eliminated by running the reaction with only 1.2 molar equivalents of HXT to PSLi and allowing the reaction to run for 15 min at −10 °C in toluene. The resulting polymer exhibited high diene chain‐end functionality and no oligomerization was observed by MALDI‐TOF MS. 13C NMR spectroscopy and the attached‐proton test (APT), along with calculated chemical shifts, showed the presence of both the 1,2‐ and 1,4‐addition chain‐end structures. Further analysis by the reaction of the functional polymer with maleic anhydride indicated that 18 wt.‐% of the product was unreactive, either because of a 1,4‐addition chain‐end structure or a nonfunctional polymer. The structure of the maleic anhydride‐modified polymer was determined by MALDI‐TOF MS and 13C NMR spectroscopy. Preliminary work on the reactivity of the diene‐functionalized macromonomers was performed by the addition of a large excess of PSLi to a solution of macromonomer followed by characterization by size‐exclusion chromatography (SEC).The formation of hexa‐1,3,5‐triene‐functionalized polystyrenes and their reaction with maleic anhydride.magnified imageThe formation of hexa‐1,3,5‐triene‐functionalized polystyrenes and their reaction with maleic anhydride.

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The Electronic Spectra of Some Anionic Polymerization Systems

Cited by 87 publications

References 11 publications

Anionic Polymerization of Isoprene

Anionic Polymerization of Isoprene

The reaction of diphenylethylenes with boron trifluoride and water

Synthesis of Diene‐Functionalized Macromonomers via Functionalization with Hexa‐1,3,5‐triene

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