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Hofmeister Effects on Poly(NIPAM) Microgel Particles: Macroscopic Evidence of Ion Adsorption and Changes in Water Structure
Author(s) -
LópezLeón Teresa,
Elaïssari Abdelhamid,
OrtegaVinuesa Juan Luis,
BastosGonzález Delfi
Publication year - 2007
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200600521
Subject(s) - chemistry , hofmeister series , adsorption , chemical physics , ionic bonding , ion , polymer , chemical engineering , phase (matter) , phase transition , electrolyte , thermodynamics , organic chemistry , physics , engineering , electrode
The term Hofmeister effects is broadly used to refer to ionic specificities in many different physical, chemical and biological phenomena. The origin of this ionic specificity is sought in two interdependent microscopic sources: 1) the peculiarities of the solvent structure near surfaces and around the ions, and 2) specific ion adsorption–exclusion mechanisms near a surface. In this work, Hofmeister effects on poly(N‐isopropylacrylamide) [poly(NIPAM)]‐based microgels are examined. Poly(NIPAM) particles are thermally sensitive microgels exhibiting volume‐phase transitions with temperature. This temperature‐sensitive system seems to be suitable for the independent observation of the two microscopic sources of Hofmeister effects. On the one hand, volume‐phase transition, evaluated by photon correlation spectroscopy (PCS), gives information about how the presence of ions changes the water structure around the poly(NIPAM) chains. On the other hand, electrokinetic studies show relevant data about ionic adsorption–exclusion phenomena at the polymer surface.