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Thermal and rheological properties of hydrophobically modified responsive gels
Author(s) -
Lowe Tao Lu,
Benhaddou Myriam,
Tenhu Heikki
Publication year - 1999
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/(sici)1521-3935(19990101)200:1<51::aid-macp51>3.0.co;2-h
Subject(s) - comonomer , polyelectrolyte , methacrylic acid , self healing hydrogels , polymer chemistry , methacrylate , swelling , chemical engineering , polymer , ionomer , aqueous solution , materials science , dynamic mechanical analysis , copolymer , chemistry , organic chemistry , composite material , engineering
Thermally responsive hydrogels have been prepared of N ‐isopropylacrylamide (NIPAAM) and a fluorinated hydrophobic comonomer, either hexafluoroisopropyl methacrylate (HFIPMA) or hexafluorobutyl methacrylate (HFBMA). Terpolymer gels containing an ionizable comonomer, methacrylic acid (MAA), were also synthesized. The swelling and mechanical properties of the gels were investigated in pure water and in aqueous NaCl solutions. All gels show thermosensitivity typical of polyNIPAAM, swelling at lower temperature and deswelling above a certain transition temperature. Hydrogels of NIPAAM and HFIPMA are homogeneous and the corresponding gel modified with methacrylic acid shows the character of a polyelectrolyte gel. However, hydrogels of NIPAAM and HFBMA are heterogeneous and the corresponding acidic gel does not behave as is typical of a polyelectrolyte gel. The acidic gel containing hexafluoroisopropyl‐substituted comonomers has a high storage modulus G' , showing that this gel favourably combines the properties of hydrophobically associating polymers and polyelectrolytes. Comparison of the macroscopic gels with chemically similar latex particles showed that the thermal behavior of the particles is mainly determined by the chemical composition but not by the residual surfactant adsorbed onto the polymer particles.