Reactivities of contact and solvent-separated ion pairs. Anionic polymerization of styrene in dimethoxyethane

1967 ◽  
Vol 89 (23) ◽  
pp. 5743-5749 ◽  
Author(s):  
Takatoshi. Shimomura ◽  
Johannes. Smid ◽  
Michael. Szwarc
Keyword(s):  
Anionic Polymerization ◽  
Ion Pairs

ANIONIC POLYMERIZATION OF STYRENE EFFECT OF TETRAHYDROFURAN

1962 ◽  
Vol 40 (8) ◽  
pp. 1564-1570 ◽  
Author(s):  
S. Bywater ◽  
D. J. Worsfold
Keyword(s):  
Anionic Polymerization ◽  
Benzene Solution ◽  
Ion Pairs ◽  
High Reactivity ◽  
Small Concentration ◽  
Kinetic Order ◽  
Highly Active ◽  
Lower Reactivity ◽  
Free Ion ◽  
Complete Breakdown

The propagation step in the butyllithium­initiated polymerization of styrene in benzene solution is thought to be due to a small concentration of highly active free ion-pairs in equilibrium with unreactive dimeric ion­pairs. This work shows that these dimers may be broken down by the addition of tetrahydrofuran. Small quantities of tetrahydrofuran form, first, a low concentration of a monoetherate of the ion­pair with a high reactivity, and this augments the propagation reaction without changing the kinetic order with respect to the initiator. This, at higher tetrahydrofuran concentrations, is followed by the complete breakdown of the dimers to give a dietherate in much higher concentration and lower reactivity compared with the initial ion­pair and monoetherate. The kinetic order with respect to the initial initiator species changes from one half to one during this process, and a maximum appears in the rate as the ether concentration increases.

Tetrabutylammonium Salts of 2-Nitropropane, Cyclopentadiene and 9-Ethylfluorene: Crystal Structures and Use in Anionic Polymerization

1995 ◽  
Vol 50 (3) ◽  
pp. 415-422 ◽  
Author(s):  
Manfred T. Reetz ◽  
Stephan Hütte ◽  
Richard Goddard
Keyword(s):  
Anionic Polymerization ◽  
Room Temperature ◽  
Ion Pairs ◽  
Three Dimensional ◽  
Star Polymers ◽  
X Ray ◽  
Dimensional Network ◽  
Acidic Compounds ◽  
Cyclopentadienyl Anion ◽  
Special Case

Reaction of the CH-acidic compounds 2-nitropropane, cyclopentadiene and 9-ethylfluorene with HON (nBu)4 affords the corresponding tetrabutylammonium salts in crystalline form, which have been characterized by X -ray structure analysis. The nitrostabilized salt is not a “naked ” anion (real carbanion). Rather, the α-methylene entities of the N+(nBu)4 cations form relatively strong hydrogen bonds with the O -atom s of the nitronateanion, forming dimers in a three-dimensional network. In solution dimers in the form of supramolecular ion pairs exist. In contrast, the cyclopentadienyl anion appears to be a real carbanion, since anion and cation do not interact with one another via H -bonding. The structure of the N+(nBu)4 salt of the 9-ethylfluorenyl anion is a special case in that closer contacts between cation and anion occur, which may be indicative of unusual [CH ··· C]- bonding. All three salts function as initiators in the metal-free anionic polymerization of acrylates and methacrylates at room temperature. In the case of tetrabutylammoniumcyclopentadienide, star polymers are formed.

Monomer Solvation of Ion Pairs in Anionic Polymerization

Nature ◽  
1967 ◽  
Vol 215 (5098) ◽  
pp. 273-274
Author(s):  
G. C. EAST ◽  
M. A. HARRISON
Keyword(s):  
Anionic Polymerization ◽  
Ion Pairs

Kinetics of Anionic Polymerization of ε-Caprolactone (εCL). Propagation of Poly-ε=CL-K+Ion Pairs

1983 ◽  
Vol 20 (9) ◽  
pp. 979-988 ◽  
Author(s):  
Stanisl Slashaw Sosnowski ◽  
Stanisl Slashaw Slomkowski ◽  
Stanisl Slashaw Penczek
Keyword(s):  
Anionic Polymerization ◽  
Ion Pairs ◽  
Kinetics Of

scholarly journals The Mechanism of the Propagation in the Anionic Polymerization of Polystyryllithium in Non-Polar Solvents Elucidated by Density Functional Theory Calculations. A Study of the Negligible Part Played by Dimeric Ion-Pairs under Usual Polymerization Conditions

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1022
Author(s):  
Hideo Morita ◽  
Marcel Van Beylen
Keyword(s):  
Density Functional Theory ◽  
Transition State ◽  
Anionic Polymerization ◽  
Density Functional ◽  
Ion Pairs ◽  
Density Functional Theory Calculations ◽  
Dft Method ◽  
Functional Theory ◽  
Elementary Processes ◽  
Rate Of Reaction

The elementary processes occurring in the anionic polymerization of styrene with dimerically associated polystyryllithium (propagation during the anionic polymerization of dimeric polystyryllithium) in the gas phase and cyclohexane were studied using MX062X/6-31+G(d), a recently developed density functional theory (DFT) method and compared with the polymerization of styrene with non-associated polystyryllithium, which was described in a previous study. The most stable transition state in the reaction of styrene with dimeric polystyryllithium has a structure in which the side chains of styrene and the two chain end units of polystyryllithium are located in the same direction around the Li atom near the reactive site. The relative enthalpy for this transition state in cyclohexane is 28 kJ·mol−1, which is much lower than that for the reaction of non-associated polystyryllithium (51 kJ·mol−1). However, the relative free energy (which determines the rate constant) for the former is 93 kJ·mol−1, which is greater than that for the latter by 7 kJ·mol−1, indicating that the latter reaction (reaction with non-associated polystyryllithium) is advantageous over the former (reaction with dimeric polystyrylllithium). Their rates of reaction are also affected by initiator concentrations; in the case of reactions with low initiator concentrations, from which high molecular weight polymers are usually obtained, the rate of reaction corresponding to non-associated polystyryllithium is much larger than that corresponding to dimeric polystyryllithium.

Effect of counter-ion in the anionic polymerization of styrene in cyclohexane

1968 ◽  
Vol 46 (16) ◽  
pp. 2711-2713 ◽  
Author(s):  
J. E. L. Roovers ◽  
S. Bywater
Keyword(s):  
Anionic Polymerization ◽  
Rate Constants ◽  
Ion Pairs ◽  
Propagation Rate ◽  
Counter Ion ◽  
Counter Ions

The propagation reaction in the anionic polymerization of styrene has been studied in cyclohexane with the counter-ions: K, Rb, and Cs. Some association of the ion-pairs was found with K. Absolute propagation rate constants were determined in the three cases. Some experiments were carried out in benzene–cyclohexane mixtures to check that the results were consistent with those previously observed in benzene.

Sign in / Sign up

Export Citation Format

Share Document