ANIONIC POLYMERIZATION OF ISOPRENE

1964 ◽  
Vol 42 (12) ◽  
pp. 2884-2892 ◽  
Author(s):  
D. J. Worsfold ◽  
S. Bywater
Keyword(s):  
Light Scattering ◽  
Anionic Polymerization ◽  
Great Increase ◽  
Major Effect ◽  
Dilute Solution ◽  
Initiation Rate ◽  
Kinetic Order ◽  
Initiation Reaction

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-quarter 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 broken down with difficulty. The microstructure of the polymer has been determined by n.m.r. measurements and shows a steady transition from a largely 1:4 to a largely 3:4 structure as the polarity of the solvent is increased by the addition of tetrahydrofuran.

Anionic Polymerization of Isoprene

1965 ◽  
Vol 38 (3) ◽  
pp. 627-635 ◽  
Author(s):  
D. J. Worsfold ◽  
S. Bywater
Keyword(s):  
Light Scattering ◽  
Anionic Polymerization ◽  
Great Increase ◽  
Major Effect ◽  
Dilute Solution ◽  
Initiation Rate ◽  
Kinetic Order ◽  
Scattering Measurements ◽  
Initiation Reaction

Abstract 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-quarter 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 broken down with difficulty. The microstructure of the polymer has been determined by NMR measurements and shows a steady transition from a largely 1:4 to a largely 3:4 structure as the polarity of the solvent is increased by the addition of tetrahydrofuran.

Aggregation behaviour of stereoregular poly(methyl methacrylates) in dilute solution: light scattering and proton n.m.r. study

Polymer ◽  
1983 ◽  
Vol 24 (6) ◽  
pp. 700-706 ◽  
Author(s):  
L. Mrkvičková ◽  
J. Stêjskal ◽  
J. Spěváček ◽  
J. Horská ◽  
O. Quadrat
Keyword(s):  
Light Scattering ◽  
Dilute Solution ◽  
Aggregation Behaviour ◽  
Methyl Methacrylates

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.

Sign in / Sign up

Export Citation Format

Share Document