Synthesis of Isoprene Tagged with C14

Korotkov, A.; Rakova, G. V.

doi:10.5254/1.3540271

Cited by 3 publications

(3 citation statements)

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“…In region II, M n,app or M n starts again to increase rapidly with time at 295 ≤ t /min ≤ 330, then followed by a slow increase to a final value. The observed two-step increase in M n,app or M n with t is well consistent with the results previously reported for the simultaneous copolymerization. , As for M w / M n , in region I at t = 30 min, the earliest accessible reaction time in this study, M w / M n is ∼1.12. As the copolymerization reaction proceeds, it gradually deceases to a constant value of 1.08, as expected.…”

Section: Resultssupporting

confidence: 93%

Combined SANS, SEC, NMR, and UV−Vis Studies of Simultaneous Living Anionic Copolymerization Process: Simultaneous Elucidation of Propagating Living Chains at Three Different Length Scales

et al. 2009

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We studied a simultaneous living anionic copolymerization of styrene (S) and isoprene (I) monomers in a dilute solution with deuterated benzene as a solvent by means of combined time-resolved measurements of small-angle neutron scattering (SANS), size exclusion chromatography (SEC), nuclear magnetic resonance (NMR), and ultraviolet-visible spectroscopy (UV-vis). We observed structural change of the living chains during the polymerization process in three different length scales on the same solution and in a single batch, which enabled us to explore simultaneously the time changes in the local structure (living chain ends), the primary structure (propagating chains), and the higher order structure (the star-like local aggregates of the living chains). We found the copolymerization process is divided into two time regions, defined by regions I and II. In region I, the copolymerization of S and I monomers occurred and all I monomers were consumed at the end of region I, while in region II, pure polystyrene (PS) block chains are formed. In the beginning of region II (region II a ), living polymers having isoprenyl anion (PI -) started to change rapidly into those having styryl anion (PS -), and followed by a slow change from PIto PSin the latter part of region II (region II b ). As a consequence of the polymerization of S monomers under the coexistence of PIand PS -, we found the following two phenomena: (i) an increase in M w /M n ; (ii) the effective conversion rate of S monomers being slow compared with the corresponding homopolymerization of S monomers. The theoretical analysis of the time-resolved SANS profiles elucidated the time change in the association number of the living chain ends n: n ∼ 4 in region I, n decreases from 4 to 2 in region II a , and n ∼ 2 in region II b .

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Section: Resultssupporting

confidence: 93%

Combined SANS, SEC, NMR, and UV−Vis Studies of Simultaneous Living Anionic Copolymerization Process: Simultaneous Elucidation of Propagating Living Chains at Three Different Length Scales

et al. 2009

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“…In region II, M n,app or M n starts to rapidly increase again with time at 7.8 ≤ t / h ≤ 10, followed by a slow increase to a final value. The observed two-step increase in M n,app or M n with t is very consistent with the results previously reported for the simultaneous copolymerization. ,, As for M w / M n , at t = 0.5 h, the earliest accessible reaction time in this study, M w / M n is ∼1.054. As the polymerization reaction proceeds, it slightly decreases to a constant value of 1.045, as expected.…”

Section: Resultssupporting

confidence: 92%

Combined SANS, SEC, NMR, and UV−vis Studies of Simultaneous Living Anionic Copolymerization Process in a Concentrated Solution: Elucidation of Building-Up Processes of Molecules and Their Self-Assemblies

et al. 2010

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A simultaneous living anionic copolymerization of a concentrated solution of deuterated styrene (S) and nondeuterated isoprene (I) monomers in deuterated benzene as a solvent was studied by a combination of time-resolved measurements of small-angle neutron scattering (SANS), size exclusion chromatography (SEC), nuclear magnetic resonance (NMR), and ultraviolet−visible spectroscopy (UV−vis). The molecular building-up process and its consequence on the bottom-up self-assembling process during the copolymerization reaction were observed on three different length scales on the same batch of the solution, which enabled us to explore simultaneously the time changes in the local structure (living chain ends), the primary structure (propagating chains), and the higher order structure (microdomains). We found that the copolymerization process was divided into two time regions, defined by regions I and II. In region I, the copolymerization of S and I monomers took place, and all I monomers were consumed at the end of region I. In the early stage of region I (region Ia), the SANS profiles were almost time-independent and exhibited no scattering maximum, whereas in the late stage of region I (region Ib), a scattering maximum appeared at q m and hardly changed with time, although the maximum intensity I m slightly increased with time. In region II, pure polystyrene (PS) block chains were formed. q m and I m rapidly decreased and increased, respectively, and the polymerization-induced disorder−order transition (ODT) and order−order transition (OOT) were observed. The living polymers having isoprenyl anion at the chain end (denoted hereafter by PI) started to change into those having styryl anion at the chain end (denoted hereafter by PS), and hence the polymerization of S monomers occurred under the coexistence of PI− and PS−. As a consequence, we found an increase in the polydispersity index of the molecular weight, M w/M n, and a slower effective reaction rate of S monomers relative to the corresponding homopolymerization of S monomers.

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“…Similar results were also obtained in the copolymerizations of DPE with butadiene and isoprene (Table V). Korotkov et al have explained the higher reactivities of butadieneu and isoprene 12 in hydrocarbon solvents by the preferential absorptions of the dienes to reaction centers. Recently, Worsfold et al 13 ' 14 found that the rates of the additions of styrene to butadienyllithium and isoprenyllithium are nearly constant whether the dienes exist in the systems or not, and denied the preferential absorptions of the dienes to lithium counter-ion in the copolymerizations of styrene with the dienes.…”

Section: Discussionmentioning

confidence: 99%

Anionic Copolymerizations of 1,1-Diphenylethylene with o- and p-Methoxystyrene

Yuki

1970

Polym J

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ABSTRACT:Anionic copolymerizations of 1,1-diphenylethylene (OPE) with o-and pmethoxystyrene (o-and p-MeOSt) were investigated with n-butyllithium (n-BuLi) and other anionic initiators. In THF, alternating copolymers ofDPE with o-andp-MeOSt were obtained. In aromatic hydrocarbons, the copolymerization of DPE and o-MeOSt with n-BuLi gave a polymer having higher o-MeOSt content, while an almost alternating copolymer was obtained in the copolymerization of DPE and p-MeOSt. The NMR spectra of the alternating copolymers of DPE with o-and p-MeOSt showed the splittings due to the tactic difference with respect to the methoxy group. The latter alternating copolymer was shown by polarized light and X-ray examinations to be crystalline.In earlier studies anionic coplymerizations of various monomer pairs were carried out to obtain information on the reactivities of the monomers and to form new polymers, 1 -5 some of which were alternating. On the other hand, o-methoxystyrene (o-MeOSt) formed a crystalline isotactic polymer in a nonpolar solvent by means of nbutyllithium (n-BuLi), but formed an atactic polymer in tetrahydrofuran (THF) 6 It was supposed that the driving force behind the formation of the isotactic poly (o-methoxystyrene) (P-o-MeOSt) was the interactions of the ether oxygens of the monomer and/or the polymer with lithium counter-ion, and the interactions were diminished in a solvent of higher solvating power such as THF.It is probable that the interaction stated above may occur in the copolymerization of o-MeOSt and 1,1-diphenylethylene (OPE), and greatly affect the reactivity. In the present paper, besides the copolymerization of these two monomers, the copolymerization of p-methoxystyrene (pMeOSt) and OPE is also studied in order to know the properties of the copolymer and the reactivity of the isomer. Materials o-MeOSt EXPERIMENTALThis was synthesized by dehydration of methyl-(2-methoxyphenyl) carbinol over acid potassium sulfate at 220--230°C, 6 and then the crude product was fractionally distilled. The monomer was dried over lithium aluminum hydride in an atmosphere of dry nitrogen, from whence it was redistilled, bp 80--81 °C (10 mmHg), nD 20 1.5605. No impurity was detected by gas chromatography or NMR spectroscopy.p-MeOSt p-MeOSt was obtained by distillation of methyl-(4-methoxyphenyl)carbinol in the presence of a small amount of hydrochloric acid. The monomer purified by distillation was dried over lithium aluminum hydride and redistilled, bp 85°C (13 mmHg), nD 20 1.5615. No impurity was detected by gas chromatography or NMR spectroscopy. DPE This was prepared by dehydration of methyldiphenylcarbinol with sulfuric acid. 7 The monomer was first stirred with Na-K alloy, and then n-BuLi inn-heptane was added until a red coloration appeared. The colored solution was fractionally distilled under dry nitrogen. The fraction . 20of bp 97-98°C (1.5 mmHg) was collected; nD 1.6085. TIIFThe solvent refluxed over lithium aluminum hydride was distilled onto benzophenone and 13

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Synthesis of Isoprene Tagged with C14

Cited by 3 publications

References 0 publications

Combined SANS, SEC, NMR, and UV−Vis Studies of Simultaneous Living Anionic Copolymerization Process: Simultaneous Elucidation of Propagating Living Chains at Three Different Length Scales

Combined SANS, SEC, NMR, and UV−Vis Studies of Simultaneous Living Anionic Copolymerization Process: Simultaneous Elucidation of Propagating Living Chains at Three Different Length Scales

Combined SANS, SEC, NMR, and UV−vis Studies of Simultaneous Living Anionic Copolymerization Process in a Concentrated Solution: Elucidation of Building-Up Processes of Molecules and Their Self-Assemblies

Anionic Copolymerizations of 1,1-Diphenylethylene with o- and p-Methoxystyrene

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