Microstructures of polybutadienes prepared by anionic polymerization in polar solvents. Ion‐pair and solvent effects

Bywater, S.; Firat, Yurdun; Black, P. E.

doi:10.1002/pol.1984.170220316

Cited by 57 publications

(40 citation statements)

References 16 publications

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“…The isomerization experiments correlate with the observations made on the effect of polymerization temperature on polybutadiene microstructure [15]. In THF with potassium as counter-ion, no change in microstructure is observed between 0° and -78°1 nor does the percentage of cis in the 1,4 units change.…”

Section: Convertsupporting

confidence: 84%

Stereospecificity in Anionic Polymerization

Bywater

1987

Recent Advances in Anionic Polymerization

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Active centers in anionic polymerization exist in cis and trans forms. Equilibrium fractions and interconversion rates depend on solvent and counter-ion. with diene polymerization in polar solvents, the isomers equilibrate rapidly down to very low temperatures if lithium is the counter-ion, but only very slowly at room temperature if it is potassium. In such solvents, the kinetic preference is trans but at equilibrium it is cis. Trans centers are more vinyl stereospecific for a given counter-ion and react faster with monomer. In vinyl polymerization, cis-trans interconversion rates are slow with all counter-ions on the reaction time scale. Counter-ion positional exchange is however rapid in THF but slows somewhat in toluene. Diad structure is not defined until the next monomer adds. The determination of 1,2 or 1,4 structure in diene polymerization is decided in the same manner, a common characteristic of anionic polymerization. 187

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Section: Convertsupporting

confidence: 84%

Stereospecificity in Anionic Polymerization

Bywater

1987

Recent Advances in Anionic Polymerization

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“…Activity [b] St found [c] Microstructures [c] M www.chemeurj.org units in the copolymer. [22] Moreover, the very strong singlet at d = 27.27 ppm indicated an unambiguously high degree of cis-1,4-PBD units (> 95 %).…”

Section: Runmentioning

confidence: 99%

A Lutetium Allyl Complex That Bears a Pyridyl‐Functionalized Cyclopentadienyl Ligand: Dual Catalysis on Highly Syndiospecific and cis‐1,4‐Selective (Co)Polymerizations of Styrene and Butadiene

Jian

Tang

Cui

2010

Chemistry A European J

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A novel linked-half-sandwich lutetium-bis(allyl) complex [(C(5)Me(4)-C(5)H(4)N)Lu(η(3)-C(3)H(5))(2)] (1) attached by a pyridyl-functionalized cyclopentadienyl ligand was synthesized and fully characterized. Complex 1 in combination with [Ph(3)C][B(C(6)F(5))(4)] exhibited unprecedented dual catalysis with outstanding activities in highly syndiotactic (rrrr>99%) styrene polymerization and distinguished cis-1,4-selective (99%) butadiene polymerization, respectively. Strikingly, this catalyst system exhibited remarkable activity (396 kg copolymer (mol(Lu) h)(-1)) for the copolymerization of butadiene and styrene. Irrespective of whether the monomers were fed in concurrent mode or sequential addition of butadiene followed by styrene, diblock copolymers were obtained exclusively, which was confirmed by a kinetics investigation of monomer conversion of copolymerization with time. In the copolymers, the styrene incorporation rate varied from 4.7 to 85.4 mol%, whereas the polybutadiene (PBD) block was highly cis-1,4-regulated (95%) and the polystyrene segment remained purely syndiotactic (rrrr>99%). Correspondingly, the copolymers exhibited glass transition temperatures (T(g)) around -107 °C and melting points (T(m)) around 268 °C; typical values for diblock microstructures. Such copolymers cannot be accessed by any other methods known to date. X-ray powder diffraction analysis of these diblock copolymers showed that the crystallizable syndiotactic polystyrene (syn-PS) block was in the toluene δ clathrate form. The AFM micrographs of diblock copolymer showed a remarkable phase-separation morphology of the cis-1,4-PBD block and syn-PS block. This represents the first example of a lutetium-based catalyst showing both high activity and selectivity for the (co)polymerization of styrene and butadiene.

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“…The 1 H and 13 C NMR spectra of polybutadiene obtained with CoX 2 are shown in Figure 10 and 11, respectively. [7][8][9] The effects of polymerization temperature, time and variation of halogen ligands on microstructure are analyzed in more details. In the 13 C NMR spectra, the resonance assignable to methylene carbon of cis-1,4 units appeared at 27.84 ppm with very high intensity.…”

Section: Effect Of Halogen Ligands On Microstructurementioning

confidence: 99%