Determination of Molecular Weight Distributions from Frequency-Analyzing (Dynamic) Light Scattering

1980 ◽  
Vol 13 (5) ◽  
pp. 1251-1254 ◽  
Author(s):  
Johannes Raczek ◽  
Guenther Meyerhoff
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Molecular Weight Distributions ◽  
Weight Distributions

Determination of Copolymer Molecular Weight

1968 ◽  
Vol 41 (1) ◽  
pp. 245-253 ◽  
Author(s):  
Paul Rempp ◽  
Henri Benoit
Keyword(s):  
Molecular Weight ◽  
Light Scattering ◽  
Density Gradient ◽  
Compositional Heterogeneity ◽  
Precise Information ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Binary Copolymers

Abstract From this brief review it appears that determinations of molecular weight averages, of molecular weight distributions, and of compositional inhomogeneity of binary copolymers, require care in the choice of techniques and methods. Some of the most commonly used techniques for molecular weight determinations on homopolymers of various kinds are inadequate for the same determinations on copolymers. Others are more sensitive to fluctuations in composition than in molecular weights. Osmotic methods are the only one which are really insensitive to inhomogeneity, and which yield molecular weights. Ultracentrifugation in a density gradient yields precise information only on fluctuations in composition. Viscosity determinations require calibration, but even so, they may lead to erroneous values of the molecular weight in the case of copolymers. GPC is less sensitive to compositional heterogeneity, but cannot be applied for nonlinear copolymers. Finally, light scattering is a very powerful tool for studies on copolymers, since it leads to molecular weight averages and its helps characterize polydispersity and fluctuations in composition.

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