The incorporation of carboxylate groups into temperature-responsive poly(N-isopropylacrylamide)-based hydrogels promotes rapid gel shrinking

Citation
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
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
ISSN journal
0887-624X → ACNP
Volume
39
Issue
3
Year of publication
2001
Pages
335 - 342
Database
ISI
SICI code
0887-624X(20010201)39:3<335:TIOCGI>2.0.ZU;2-F
Abstract
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.