Modification of calibration curve for measurement of molecular weight of small polymers by gel permeation chromatography

Abstract

When the molecular weight of a polymer is so small ( M < 10 000) that the Mark-Houwink-Sakurada (MHS) constants depend on M, the use of the MHS equation is not appropriate to modify a calibration curve made from standard polymer samples into curves to measure molecular weights of the respective polymers by gel permeation chromatography. Here, such a modification is tried by the Dondos-Benoit (BD) equation: 1 [η] = − A 2 + A 1 M 1 2 ([ η] = intrinsic viscosity; A 1, A 2 = constants), with polystyrene and polybutadiene used as the polymer samples. It is shown that the modification is adoptable for M < 50 000 for polystyrene and for M < 23 600 for polybutadiene. It is also shown that, using the MHS equation when M is high and the BD equation when M is low, a calibration curve made from standard polymer samples can be modified into curves to measure molecular weights of the respective polymers over the whole range of molecular weight.