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Physical Gelation of Amphiphilic Poly( N ‐isopropylacrylamide): Influence of the Hydrophobic Groups
Author(s) -
Wintgens Véronique,
Amiel Catherine
Publication year - 2008
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.200800093
Subject(s) - poly(n isopropylacrylamide) , lower critical solution temperature , amphiphile , polymer chemistry , copolymer , rheology , viscoelasticity , aqueous solution , dynamic light scattering , phase transition , hydrophobic effect , chemical engineering , phase (matter) , chemistry , materials science , polymer , thermodynamics , organic chemistry , nanotechnology , composite material , nanoparticle , physics , engineering
Abstract The self‐assembling properties of hydrophobically modified ( N ‐isopropylacrylamide) have been investigated by dynamic light scattering and rheological measurements. Size of the globules and transmission of the solutions vary strongly in the same range of temperature. The presence of hydrophobic groups leads to contraction of the globules' size compared to poly( N ‐isopropylacrylamide) (PNIPAM). The viscoelastic properties of the samples in aqueous solution have been investigated as a function of copolymer concentration, structure of the hydrophobic group (dodecyl or adamantyl group), substitution level (1–5%) and over a temperature range covering the lower critical solution temperature (LCST). At high concentration and high level of adamantyl substitution, gelation is observed several degrees before the phase transition. A physical network is formed due to the strong hydrophobic interactions, and this physical gel undergoes phase transition without macroscopic phase separation.