Premium
Temperature and pH effects on the stability and rheological behavior of the aqueous suspensions of smart polymers based on N ‐isopropylacrylamide, chitosan, and acrylic acid
Author(s) -
do Nascimento Marques Nívia,
Curti Priscila Schroeder,
da Silva Maia Ana Maria,
Balaban Rosangela de Carvalho
Publication year - 2012
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.38750
Subject(s) - poly(n isopropylacrylamide) , acrylic acid , ammonium persulfate , chemical engineering , potassium persulfate , rheology , chitosan , aqueous solution , materials science , lower critical solution temperature , polymer chemistry , polymer , copolymer , particle (ecology) , chemistry , composite material , organic chemistry , polymerization , oceanography , engineering , geology
This study describes the stability and rheological behavior of suspensions of poly( N ‐isopropylacrylamide) (PNIPAM), poly( N ‐isopropylacrylamide)‐chitosan (PNIPAM‐CS), and poly( N ‐isopropylacrylamide)‐chitosan‐poly(acrylic acid) (PNIPAM‐CS‐PAA) crosslinked particles sensitive to pH and temperature. These dual‐sensitive materials were simply obtained by one‐pot method, via free‐radical precipitation copolymerization with potassium persulfate, using N,N ′‐methylenebisacrylamide as a crosslinking agent. Incorporation of the precursor materials into the chemical networks was confirmed by elementary analysis and infrared spectroscopy. The influence of external stimuli such as pH and temperature, or both, on particle behavior was investigated through rheological measurements, visual stability tests, and analytical centrifugation. The PNIPAM‐CS particles showed higher stability in acid and neutral media, whereas PNIPAM‐CS‐PAA particles were more stable in neutral and alkaline media, both below and above the lower critical solution temperature of PNIPAM (stability data). This is due to different interparticle interactions as well as those between the particles and the medium (also evidenced by rheological data), which were also influenced by the pH and temperature of the medium. Based on the results obtained, we found that the introduction of pH‐sensitive polymers to crosslinked PNIPAM particles not only produced dual‐sensitive materials but also allowed particle stability to be adjusted, making phase separation faster or slower, depending on the desired application. Thus, it is possible to adapt the material to different media. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013