M. Ebara et al., The incorporation of carboxylate groups into temperature-responsive poly(N-isopropylacrylamide)-based hydrogels promotes rapid gel shrinking, J POL SC PC, 39(3), 2001, pp. 335-342
Citations number
19
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
Aqueous gel deswelling rates for copolymer hydrogels comprising N-isopro-py
lacrylamide (IPAAm) and 2-carboxyisopropylacrylamide (CIPAAm) in response t
o increasing temperatures were investigated. Compared with pure IPAAm-based
gels, IPAAm-CIPAAm gels shrink very rapidly in response to small temperatu
re increases across their lower critical solution temperature (their volume
is reduced by five-sixths within 60 s). Shrinking rates for these hydrogel
s increase with increasing CIPAAm content. In contrast, structurally analog
ous IPAAm-acrylic acid (AAc) copolymer gels lose their temperature sensitiv
ity with the introduction of only a few mole percent of AAc. Additionally,
deswelling rates of IPAAm-AAc gels decrease with increasing AAc content. Th
ese results indicate that IPAAm-CIPAAm copolymer gels behave distinctly fro
m IPAAm-AAc systems even if both comonomers, CIPAAm and AAc, possess carbox
ylic acid groups. Thus, we propose that the sensitive deswelling behavior f
or lPAAm-CIPAAm gels results from strong hydrophobic chain aggregation main
tained between network polymer chains due to the similar chemical structure
s of CIPAAm and IPAAm. This structural homology facilitates aggregation of
chain isopropylamide groups for both IPAAm and CIPAAm sequences with increa
sing temperature. The incorporation of AAc, however, shows no structural ho
mology to IPAAm, inhibiting chain aggregation and limiting collapse. A func
tionalized temperature-sensitive poly(N-isopropylacrylamide) hydrogel conta
ining carboxylic acid groups is possible with CIPAAm, producing rapid and l
arge volume changes in response to smaller temperature changes. (C) 2000 Jo
hn Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 335-342, 2001.