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Number‐average molecular weight of branched polymers from SEC with viscosity detection and universal calibration
Author(s) -
Netopilík Miloš,
Podešva Jiří,
Lokaj Jan,
Kratochvíl Pavel
Publication year - 2008
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.2458
Subject(s) - polymer , intrinsic viscosity , molar mass distribution , size exclusion chromatography , divinylbenzene , calibration , viscosity , gel permeation chromatography , materials science , styrene , copolymer , molecular mass , calibration curve , branching (polymer chemistry) , polymer chemistry , chemistry , thermodynamics , analytical chemistry (journal) , chromatography , organic chemistry , mathematics , physics , detection limit , composite material , statistics , enzyme
BACKGROUND: Number‐average molecular weight, M̄ n , is an important characteristic of synthetic polymers. One of the very few promising methods for its determination is size‐exclusion chromatography (SEC) using on‐line viscometric detection and assuming the validity of the universal calibration concept. RESULTS: We have examined the applicability of this approach to the characterization of statistically branched polymers using 22 copolymers of styrene and divinylbenzene as well as 3 homopolymers of divinylbenzene with various degrees of branching. SEC with three on‐line detectors, i.e. concentration, light scattering and viscosity, enables us to evaluate experimental data by various computational procedures yielding M̄ n and weight‐average molecular weight, M̄ w . Analysis of the results has shown that the universal calibration theorem has limited validity, apparently due to the dependence of the Flory viscosity function on the molecular shape, the molecular weight distribution and the expansion of molecules. CONCLUSION: For complex polymers, the universal calibration, i.e. the dependence of the product of intrinsic viscosity and molecular weight, [η] M , on elution volume, can differ in values of [η] M from those obtained for narrow molecular weight standards by 10–15%. The method studied is helpful for the determination of M̄ n of polymers, in particular of those with very broad molecular weight distribution, such as statistically highly branched polymers. Copyright © 2008 Society of Chemical Industry