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Dynamic viscoelasticity study of the phase transition of poly( N ‐isopropylacrylamide)
Author(s) -
Hsu Shanhui,
Yu TzyyLung
Publication year - 2000
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/(sici)1521-3927(20000501)21:8<476::aid-marc476>3.0.co;2-o
Subject(s) - lower critical solution temperature , viscoelasticity , rheology , dynamic light scattering , poly(n isopropylacrylamide) , phase transition , rheometer , polymer chemistry , critical point (mathematics) , materials science , gel point , critical exponent , thermodynamics , cloud point , polymer , composite material , copolymer , physics , nanotechnology , mathematics , mathematical analysis , pulmonary surfactant , nanoparticle
The phase transition of poly( N ‐isopropylacrylamide) (poly(NIPAM)) solutions was characterized by a dynamic fluid rheometer. Two critical points were observed below the lower critical solution temperature (LCST; ∼31.5°C): (1) a critical point resembling sol‐gel transition occurs at ∼28.5°C, not far beyond the onset of elasticity (∼28.2°C), and (2) a second critical point appears at ∼30.4 °C corresponding to the reported Flory temperature ( Θ ). These findings suggest that intermolecular association and coil‐globule transition of poly(NIPAM) occur below the LCST. The fractal dimension of association of poly(NIPAM) chains which was calculated based upon the rheological method (∼1.49) is close to that determined by static light scattering.