Premium
Determination of number‐average and weight‐average molecular weights of polymer sample from diffusion and sedimentation velocity measurements in theta solvent
Author(s) -
Okabe Masaru,
Matsuda Hideomi
Publication year - 1983
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1983.070280717
Subject(s) - cyclohexane , polystyrene , molar mass distribution , diffusion , theta solvent , polymer , analytical chemistry (journal) , chemistry , fractionation , solvent , dispersity , thermodynamics , chromatography , materials science , polymer chemistry , solvent effects , physics , organic chemistry
Several methods to determine number‐average molecular weight M n and weight‐average molecular weight M w , of a polymer sample are proposed from diffusion and sedimentation velocity measurements at the θ point. According to these methods, M n and M w are determined from the diffusion constant vs. molecular weight relationship, and also from the equations of Svedberg and Flory–Mandelkern, using the 2nd‐order and the –2nd‐order diffusion constants. These methods have been applied to four samples of polydisperse polystyrene in the θ solvent, cyclohexane at 35°C. It was experimentally ascertained that M n and M w of each sample determined by the present methods were in good agreement with the results of column fractionation, light scattering, and calculated values from molecular weight distribution curve within experimental errors. It is concluded that the present methods are useful for determining M n and M w , since the reliabilities of M n and M w values, which are fundamental quantities of polymer characterization, can be raised by comparing the experimental data observed by conventional methods such as osmotic pressure, light scattering, and the Archibald method with those observed by the present methods.