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Reentrant Phase Transition of Strong Polyelectrolyte Poly( N ‐isopropylacrylamide) Gels in PEG Solutions
Author(s) -
Melekaslan Demet,
Okay Oguz
Publication year - 2001
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 - 10.1002/1521-3935(20010101)202:2<304::aid-macp304>3.0.co;2-x
Subject(s) - self healing hydrogels , polyelectrolyte , polymer chemistry , peg ratio , swelling , ethylene glycol , poly(n isopropylacrylamide) , chemistry , chemical engineering , aqueous solution , sulfonic acid , ionic bonding , materials science , copolymer , polymer , organic chemistry , ion , finance , engineering , economics
The swelling behavior of a series of strong polyelectrolyte hydrogels based on N‐ isopropylacrylamide (NIPA) and 2‐acrylamido‐2‐methylpropane sulfonic acid sodium salt (AMPS) was investigated in aqueous solutions of poly(ethylene glycol)s (PEG) of molecular weights 300 and 400 g/mol. Non‐ionic hydrogels or hydrogels with 1 mol‐% AMPS deswell with increasing PEG‐300 volume fraction ϕ in the external solution up to ϕ = 0.6. As ϕ is further increased, the hydrogels start to swell up to ϕ = 1. The distribution of PEG inside and outside the gel phase changes with the gel volume; PEG chains first move from the gel to the solution phase from ϕ = 0 to 0.6, while at higher ϕ values they again penetrate the gel phase. In PEG‐400 solutions, the contraction of the gels is jumpwise first‐order phase transition at a critical ϕ, while their reswelling occurs smoothly at higher values of ϕ. Calculations using the Flory‐Huggins theory indicate attractive interactions between PEG and PNIPA segments, which are responsible for the observed reentrant transition behavior.