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Thermoresponsive Poly(Ionic Liquid)s in Aqueous Salt Solutions: Salting‐Out Effect on Their Phase Behavior and Water Absorption/Desorption Properties
Author(s) -
Okafuji Akiyoshi,
Kohno Yuki,
Ohno Hiroyuki
Publication year - 2016
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.201500752
Subject(s) - lower critical solution temperature , salting out , aqueous solution , chemistry , desorption , monomer , polymer chemistry , ionic liquid , alkyl , absorption (acoustics) , polymerization , copolymer , materials science , adsorption , polymer , organic chemistry , catalysis , composite material
Here, a thermoresponsive phase behavior of polymerized ionic liquids (PILs) composed of poly([tri‐ n ‐alkyl(vinylbenzyl)phosphonium]chloride) (poly([P nnn VB ]Cl) is reported, where n (the number of carbon atoms of an alkyl chain) = 4, 5, or 6 after mixing with aqueous sodium chloride solutions. Both monomeric [P 555VB ]Cl and the resulting poly([P 555VB ]Cl) linear homopolymer show a lower critical solution temperature (LCST)‐type phase behavior in aq. NaCl solutions. The phase transition temperature of the PIL shifts to lower value by increasing concentration of NaCl. Also the swelling degree of cross‐linked poly([P 555VB ]Cl) gel decreases by increasing NaCl concentration, clearly suggesting the “salting‐out” effect of NaCl results in a significant dehydration of the poly([P 555VB ]Cl) gel. The absorbed water in the PIL gel is desorbed by moderate heating via the LCST behavior, and the absolute absorption/desorption amount is improved by copolymerization of [P 555VB ]Cl with more hydrophilic [P 444VB ]Cl monomer.