Polymer molecular weight, light scattering

Ederle and Mathis, in a very careful study, recently showed by SEC with combined mass and molecular weight (light scattering) detectors that exactly six polystyryllithium chains can be coupled with pure fullerene (C60) in toluene. Furthermore, comparison of the mass and UV (set at 320 nm sensitive to the presence of C60) traces proved the uniformity of the C60 core in the star polymer [49],... 

Synchropak columns are very useful for characterizing hydrophilic, anionic, and nonionic, water-soluble polymers, CATSEC columns work best for characterizing cationic polymers utilizing both light scattering and/or differential viscometry detection over a wide range of molecular weights. 

DETERMINATION OF MOLECULAR WEIGHTS AND POLYMER DIMENSIONS BY LIGHT SCATTERING... 

Light scattering from solutions can be used to measure Molecular weights as low as that of sucrose and as high as those of proteins. In actual practice, polymer Molecular weights are of the order of 10,000-10,000,000 and can readily be measured. The method has been used for determination of absolute values... 

Polystyrene can be prepared as follows A mixture of styrene, detergent (Na-dodecanoate), and water is agitated ultrasonically to produce a fine emulsion. On the addition of hydrogen peroxide (initiator), PS is obtained as a polymer, which can be extracted after filtration. The polymer molecular weight is determined by various methods (such as light scattering and osmotic pressure). 

Spectrofluorimeters as Light-Scattering Apparatus Application to Polymers Molecular Weight Determination 122... 

Kulicke W-M, Kniewske R (1980) Purification of aqueous and non-aqueous polymer solutions for light scattering measurements and a comparison of molecular weights determined with a low-angle and a wide-angle-photometer Makromol Chem, Rapid Commun 1 719... 

Introduction of two very important physical techniques in polymer science, viz. Light Scattering for molecular weight determination (by Debye) and Infra-red Spectroscopy for structural analysis (by Thompson)... 

An alternative is to determine the polymers molecular weight/mass in the SEC eluent in situ, by use of on-line molecular mass sensitive detectors. Two such detectors are commercially available, the light scattering detector and the viscosity detector. These detectors are usually used in series with a mass concentration detector and require specialised data handling/software to compute the outputs from the twin detectors and to produce molecular weight/masses and distributions. 

By comparison, free-radical butadiene polymerization in aqueous emulsion typically yields polymers with 60% trans-incorporated units under similar conditions [22]. Polymer molecular weights of 2.6 x 10" g mol were determined by light scattering [21]. 

Viscometry is the most widely used method for the characterization of polymer molecular weight because it provides the easiest and most rapid means of obtaining molecular weight related data and requires a minimum amount of instrumentation. A most obvious characteristic of polymer solutions is their high viscosity, even when the amount of added polymer is small. Even so, because viscometry does not yield absolute values of M, one must calibrate the viscometry results with values obtained for the same polymer and solvent by using an absolute technique such as light scattering photometry. 

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