Molecular Weight Distributions in Nitroxide-Mediated Living Free Radical Polymerization:  Kinetics of the Slow Equilibria between Growing and Dormant Chains

1996 ◽  
Vol 29 (10) ◽  
pp. 3346-3352 ◽  
Author(s):  
Richard P. N. Veregin ◽  
Peter G. Odell ◽  
Lora M. Michalak ◽  
Michael K. Georges
Keyword(s):  
Molecular Weight ◽  
Free Radical ◽  
Radical Polymerization ◽  
Free Radical Polymerization ◽  
Polymerization Kinetics ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Living Free Radical Polymerization ◽  
Kinetics Of

The Kinetics of Free-Radical Polymerization: Fundamental Aspects

2002 ◽  
Vol 55 (7) ◽  
pp. 399 ◽  
Author(s):  
G. T. Russell
Keyword(s):  
Molecular Weight ◽  
Steady State ◽  
Free Radical ◽  
Radical Polymerization ◽  
Chain Length ◽  
Free Radical Polymerization ◽  
Length Dependence ◽  
Model Independent ◽  
Living Free Radical Polymerization ◽  
Kinetics Of

Some fundamental aspects of the kinetics of free-radical polymerization are reviewed. So-called classical results for rate and molecular-weight distribution are first of all presented. It is shown how this approach can be built upon when chain-length-dependent termination is allowed, which it always should be. Various termination models are considered, and it is illustrated that although the models are different, rather remarkably they give common, model-independent behaviour. Some leading experimental results regarding the chain-length dependence of termination are summarized, before the chain-length dependence of other reactivities, the variation of reactivities with conversion, and non-steady state experiments are briefly discussed. Finally, living free-radical polymerization as effected by a reversible termination agent is considered. An outline of the kinetics of these systems is given, with the oft-neglected importance of conventional termination being stressed.

General Solution to the Band-Broadening Problem in Polymer Molecular Weight Distributions

2005 ◽  
Vol 58 (3) ◽  
pp. 178 ◽  
Author(s):  
Jeffrey V. Castro ◽  
Kim Y. van Berkel ◽  
Gregory T. Russell ◽  
Robert G. Gilbert
Keyword(s):  
Molecular Weight ◽  
Free Radical ◽  
Radical Polymerization ◽  
Free Radical Polymerization ◽  
Size Exclusion ◽  
Full Detail ◽  
Band Broadening ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Exclusion Chromatography

A method is developed for overcoming the problem of band broadening (where a sample which is monodisperse in molecular weight elutes over a range of elution volumes) in order to obtain accurate molecular weight distributions of polymers using size exclusion chromatography (SEC). It is proved that the SEC signal from an exponential number distribution (as obtained from free-radical polymerization under certain conditions) has the same functional form at the maximum, irrespective of band broadening. This leads to a method for quantifying the band broadening from any SEC trace, and hence for deconvoluting the trace to obtain the true distribution—by free-radical polymerization one should synthesize ‘standards’ which have exponential distributions and then carry out least-squares fitting to find the corresponding broadening function. The new method opens the way for mechanistic understanding and rate parameters to be obtained from the full detail that has hitherto been inaccessible in molecular weight distributions.

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