Moderated copolymerization. Part 2.—Transfer constant of styryl radicals towards carbon tetrabromide: a penultimate unit effect in chain transfer

1978 ◽  
Vol 74 (0) ◽  
pp. 1020 ◽  
Author(s):  
Clement H. Bamford ◽  
Sulaiman N. Basahel
Keyword(s):  
Chain Transfer ◽  
Transfer Constant ◽  
Carbon Tetrabromide

Methyl methacrylate polymerization involving a cobalt ortho-iminobenzosemiquinone complex: Determination of the chain transfer constant

2015 ◽  
Vol 56 (3) ◽  
pp. 267-275 ◽  
Author(s):  
E. V. Kolyakina ◽  
Yu. E. Ovchinnikova ◽  
I. D. Grishin ◽  
A. I. Poddel’skii ◽  
D. F. Grishin
Keyword(s):  
Methyl Methacrylate ◽  
Chain Transfer ◽  
Transfer Constant ◽  
Methyl Methacrylate Polymerization ◽  
Chain Transfer Constant

Studies in chain transfer II. Catalyzed polymerization of methyl methacrylate

1952 ◽  
Vol 214 (1117) ◽  
pp. 247-262 ◽  
Keyword(s):  
Methyl Methacrylate ◽  
Benzoyl Peroxide ◽  
Chain Transfer ◽  
Monomer Concentration ◽  
Bulk Polymerization ◽  
Transfer Constant ◽  
Initiation Mechanism ◽  
Low Concentrations ◽  
High Concentrations ◽  
Predicted Values

The chain-transfer reaction between growing methyl methacrylate ( M ) polymer radical and toluene ( S ) when catalyzed by varying quantities of benzoyl peroxide ( B ) at 80 and 60°C and p -nitrobenzoyl peroxide at 80°C has been studied. It has been established that the transfer constant calculated from the slope of 1/ P̄ against S / M curve at constant B / M is not affected by the presence of low concentrations of benzoyl peroxide ( B ), which opens up the possibility of using catalysts for chain-transfer studies. At high concentrations of the catalyst, p -nitrobenzoyl peroxide, the calculated transfer constant has been found to be appreciably altered due to transfer with the catalyst itself. A crucial experimental test of whether the initiation mechanism is unimolecular or bimolecular has been made. In conformity with the deduction from the latter mechanism it has been found that at a constant monomer concentration 1/ P̄ against √( B / M ) plot is linear, and the slope of this line remains unaffected by a change of monomer concentration. On the contrary, the alternative deduction based on unimolecular initiation that 1/ P̄ against √( B / M ) plot should be linear and of equal slope at all monomer concentrations is found inconsistent with experimental data. This strongly supports bimolecular initiation and definitely dis­counts the idea of monomolecular initiation by the catalyst. Four probable mechanisms from literature which are equivalent to a bimolecular mechanism are discussed. A critical test of the whole scheme has been made by calculating D. P. values in bulk polymerization by extrapolation from our data in solution. These extrapolated values are used to construct 1/ P̄ against √( B / M ) curves, and these latter curves are compared with similar curves based on experimentally determined data. A fair degree of concordance between the predicted and the observed values, the predicted values being somewhat lower, is obtained, confirming the essential correctness of the assumed mechanisms of polymeriza­tion and chain transfer.

Radical telomerization of 3,3,3-trifluoro-1-propene by carbon tetrabromide. Individual chain transfer constants

1987 ◽  
Vol 36 (4) ◽  
pp. 734-737
Author(s):  
T. T. Vasil'eva ◽  
V. A. Kochetkova ◽  
B. V. Nelyubin ◽  
B. I. Dostovalova ◽  
R. Kh. Freidlina
Keyword(s):  
Chain Transfer ◽  
Carbon Tetrabromide ◽  
Radical Telomerization

CHAIN TRANSFER CONSTANT OF VINYLPYRROLIDONE WITH DEXTRAN

1962 ◽  
Vol 66 (5) ◽  
pp. 828-829 ◽  
Author(s):  
Kwei-ping S. Kwei ◽  
F. R. Eirich
Keyword(s):  
Chain Transfer ◽  
Transfer Constant ◽  
Chain Transfer Constant

scholarly journals Effect of bulky 2,6-bis(spirocyclohexyl)-substituted piperidine rings in bis(hindered amino)trisulfide on thermal healability of polymethacrylate networks

2021 ◽  
Author(s):  
Motohiro Aiba ◽  
Take-aki Koizumi ◽  
Kazuaki Okamoto ◽  
Motoshi Yamanaka ◽  
Michinari Futamura ◽  
...  
Keyword(s):  
Chain Transfer ◽  
Moderate Temperature ◽  
Transfer Constant ◽  
Chain Transfer Constant

Bulky 2,6-bis(spirocyclohexyl)-substituted piperidine rings in bis(hindered amino)trisulfide affords low chain-transfer constant and thermal healability at moderate temperature.

scholarly journals Further Effects of Chain-Length-Dependent Reactivities on Radical Polymerization Kinetics

2007 ◽  
Vol 60 (10) ◽  
pp. 754 ◽  
Author(s):  
Johan P. A. Heuts ◽  
Gregory T. Russell ◽  
Gregory B. Smith
Keyword(s):  
Molecular Weight ◽  
Radical Polymerization ◽  
Chain Length ◽  
Chain Transfer ◽  
Transfer Constant ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
A Chain ◽  
Chain Transfer Constant ◽  
Independent Chain

In the present paper, we finalize some threads in our investigations into the effects of chain-length-dependent propagation (CLDP) on radical polymerization kinetics, confirming all our previous conclusions. Additionally, and more significantly, we uncover some unexpected and striking effects of chain-length-dependent chain transfer (CLDTr). It is found that the observed overall rate coefficients for propagation and termination (and therefore the rate of polymerization) are not significantly affected by whether or not chain transfer is chain-length dependent. However, this situation is different when considering the molecular weight distributions of the resulting polymers. In the case of chain-length-independent chain transfer, CLDP results in a considerable narrowing of the distribution at the low molecular weight side of the distribution in a chain-transfer controlled system. However, the inclusion of both CLDP and CLDTr yields identical results to classical kinetics – in these latter two cases, the molecular weight distribution is governed by the same chain-length-independent chain transfer constant, whereas in the case of CLDP only, it is governed by a chain-length-dependent chain transfer constant that decreases with decreasing chain length, thus enhancing the probability of propagation for short radicals. Furthermore, it is shown that the inclusion of a very slow first addition step has tremendous effects on the observed kinetics, increasing the primary radical concentration and thereby the overall termination rate coefficient dramatically. However, including possible penultimate unit effects does not significantly affect the overall picture and can be ignored for the time being. Lastly, we explore the prospects of using molecular weight distributions to probe the phenomena of CLDP and CLDTr. Again, some interesting insights follow.

Chain-Transfer Constant

2016 ◽  
Author(s):  
Stanisław Penczek ◽  
Graeme Moad
Keyword(s):  
Chain Transfer ◽  
Transfer Constant ◽  
Chain Transfer Constant
Sign in / Sign up

Export Citation Format

Share Document