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What is the Contribution of Counter‐Ions to the Absolute Molar Mass of Polyelectrolytes Determined by SEC‐MALLS?
Author(s) -
Gonzalez Philippe,
Leclercq Laurent,
Cottet Hervé
Publication year - 2016
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201600295
Subject(s) - molar mass , polyelectrolyte , chemistry , monomer , polymerization , cationic polymerization , degree of polymerization , ion , polymer , polymer chemistry , intrinsic viscosity , analytical chemistry (journal) , chromatography , organic chemistry
In this work, the absolute molar mass of well‐defined cationic polyelectrolytes has been determined by size‐exclusion chromatography multiangle laser light scattering (SEC‐MALLS) using different eluents containing different counter‐ions (chloride, bromide or trifluoroacetate). Narrowly polydisperse poly‐ l ‐lysines of different degrees of polymerization (from 20 up to ≈400) having a counter‐ion similar to the eluent are analyzed as model compounds. By comparing the average degree of polymerization obtained by SEC‐MALLS with those derived independently from NMR/viscosity experiments, it has been possible to investigate what is the average molar mass of the charged monomer that is measured in SEC‐MALLS experiments. The main result of this study is that the average molar mass of the charged monomer in a SEC‐MALLS experiment only takes into account the fraction of condensed counter‐ion associated to the monomer. This fundamental study is important in practice because the calculation of the degree of polymerization (instead of the molar mass) is often required for subsequent chemical reactions, for instance in the case of polymer functionalization.