Molecular weights and sizes of polymers

A more satisfying procedure for determining molecular weight and size of polymer molecules by light scattering was developed by Zirnm. The method is based on the same general principle of destructive interference... 

Fia. 15-13. Use of light scattering for determining molecular weight and size of polymer molecules. Zimm plot of polystyrene in diehloroethylene at 22°C. [Otder, Carr, and Zivm, J. Chem. Pkys. 18, 830 (1950).]... 

Most of the methods for determining the molecular weights and sizes of polymers (with the exception of small-angle neutron scattering) require dissolving the polymers in proper solvents first. The measurements are then carried out on dilute solutions. 

Each monomer addition involves the reaction between two hydroxyl groups, and a monomer can react as readily with a functional group on the end of a polymer as with another monomer. Initially, however, a monomer is far more likely to encounter another monomer than any other reactive molecule because these are the most prevalent species. The first stages of the reaction produce dimers which are likely in turn to yield trimers or tetramers by reacting with monomers or other dimers. There is thus a gradual increase in the average size of the species in the reaction mixture, and the molecular weight and yield of polymer both increase as the reaction proceeds. 

Determination of Molecular Weight and Size of Ultrahigh Molecular Weight Polymers Using Thermal Field-Flow Fractionation and Light Scattering... 

The light scattering technique has been principally used in polymer science for the study of the molecular weight and size of molecules in... 

The polymer characterization deals with the molecular weight and size of the particles. As regards to molecular weight it is customary to use a parameter obtained from relative viscosity measurements of dilute solutions, termed the K-value. The common range is 40 to 70, corresponding to M = 20,000 -50,000 and = 50,000 - 260,000. The molecular weight distribution is apparently rather narrow. The size and distribution of the particles as well as... 

Puskas, J.E. et al. Comparison of molecular weight and size measurement of polyisobutylenes by SEC-MALLS and viscometry, J. Polym. Sci. Chem., 44, 1777, 2006. 

Elemental analyses were performed by Galbraith Laboratories, Inc., of Knoxville, TN. The compositions of the HS-MOTSS copolymers were derived from the average of the values calculated from the reported halogen and silicon content. The molecular weight and dispersity of the polymers were measured in tetrahydrofuran by size... 

For branched polymers, molecular size is crucial because the material eluting at any value of Vr consists of a mixture of species having different molecular weights and degrees of branching but constant hydrodynamic volume. 

Rayleigh X Rs, particle size Applicable for (R/X) < 1/20 extension of the Rayleigh equation to solutions allows the measurement of osmotic pressure, molecular weight, and turbidity of colloidal or polymer solutions see Section 5.3... 

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