The “SIZE” of Macromolecules and Some Observations on Their Mass

Abstract

The determination of the “radius of gyration” by light scattering (LS) techniques is reexamined in view of some misunderstandings of the concept presented in a recent paper. Light scattering measurements made over a broad range of scattering angles may be used to extract this mean square radius even though the initial slope of the scattering variation may be experimentally inaccessible. The underlying theory and measurement precision (which can result in erroneous conclusions) are examined and discussed. The combination of HPSEC/LS (with universal calibration) permits deduction of molecular size for certain linear polymers that would be inaccessible to light scattering alone. The measurements of number and weight average molecular weights by viscometry and LS are discussed in view of recent developments.