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Dextran‐Based Polycations: Thermodynamic Interaction with Water as Compared With Unsubstituted Dextran, 2 – Flory/Huggins Interaction Parameter
Author(s) -
Bercea Maria,
Nichifor Marieta,
Eckelt John,
Wolf Bernhard A.
Publication year - 2011
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.201100197
Subject(s) - flory–huggins solution theory , dextran , monomer , polymer , chemistry , dilution , thermodynamics , volume fraction , polymer chemistry , chromatography , organic chemistry , physics
The Flory‐Huggins interaction parameter χ is determined as a function of volume fraction of polymer φ by vapor‐pressure measurements at 25, 37.5 and 50 °C for five dextran samples that differ in f , the fraction of randomly distributed charged monomer units. The function χ ( φ ) has a minimum that is shifted towards lower χ values as f increases. The higher the temperature, the more the individual curves fan out. The heats of dilution at high polymer concentrations change from exothermal to endothermal as f increases. The results can be well modeled by an approach accounting explicitly for chain connectivity and conformational changes. A smooth transition of the solution properties upon the random introduction of charged units into dextran is observed.