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Lower critical solution temperature determination of smart, thermosensitive N ‐isopropylacrylamide‐ alt ‐2‐hydroxyethyl methacrylate copolymers: Kinetics and physical properties
Author(s) -
Fares Mohammad M.,
Othman Ali A.
Publication year - 2008
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.28840
Subject(s) - lower critical solution temperature , copolymer , differential scanning calorimetry , monomer , polymer chemistry , materials science , methacrylate , activation energy , thermogravimetric analysis , arrhenius equation , reactivity (psychology) , chemistry , polymer , thermodynamics , organic chemistry , composite material , physics , medicine , alternative medicine , pathology
The lower critical solution temperatures (LCSTs) were verified and determined for different molar feed ratios of N ‐isopropylacrylamide (NIPAAm) and 2‐hydroxyethyl methacrylate (HEMA) monomers with ultraviolet spectroscopy and differential scanning calorimetry techniques. Increases in the NIPAAm monomer content played a crucial role in the LCST, which increased up to 36.7°C at 50 mol %. However, a further increase in the NIPAAm monomer content steadily reduced the LCST, which decreased to 33°C at 100 mol % NIPAAm [i.e., pure poly( N ‐isopropylacrylamide)]. The rate of copolymerization, assessed by the conventional conversion (%)–time method, and the apparent activation energies were determined. The reactivity ratios of the monomers, determined by the Kelen–Tudos and Fineman–Ross techniques, together with the results of an equation, showed that the copolymer which formed was an alternating copolymer. The Q – e values for the NIPAAm monomer were determined. The equation showed the linear Arrhenius behavior of ln( r 1 r 2 ) versus the reciprocal of the temperature (where r 1 and r 2 are the reactivity ratios of NIPAAm and HEMA, respectively): the activation energy difference [i.e., ( E 12 + E 21 ) − ( E 11 + E 22 ), where E 12 , E 21 , E 11 , and E 22 are various activation energies] was found to be −109 kJ/mol. The copolymers were characterized with 1 H‐NMR, 13 C‐NMR, Fourier transform infrared, ultraviolet–visible, thermogravimetric analysis, differential scanning calorimetry, X‐ray diffraction, and scanning electron microscopy techniques. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008