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High strength thermoresponsive semi‐IPN hydrogels reinforced with nanoclays
Author(s) -
Djonlagić Jasna,
Žugić Dragana,
Petrović Zoran
Publication year - 2011
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.35334
Subject(s) - self healing hydrogels , swelling , ultimate tensile strength , lower critical solution temperature , materials science , elongation , poly(n isopropylacrylamide) , composite material , elastic modulus , chemical engineering , polymer chemistry , polymer , copolymer , engineering
Two series of nanoclay reinforced, thermoresponsive hydrogels were prepared, one based on poly( N ‐isopropylacrylamide) (PNIPA) and the other on semi‐interpenetrating networks containing PNIPA and poly( N ‐vinyl pyrrolidone) (PVP), designated as SIPNs. The gels were crosslinked with 1, 3, and 5 wt % inorganic clay (hectorite) and SIPN gels additionally contained 1 wt % of PVP. The hydrogels were tested in the “as‐prepared state,” i.e., at 10 wt % PNIPA concentration in water and at equilibrium (maximum) swelling. Increasing the concentration of nanoclays increases crosslink density, modulus, tensile strength, elongation (except in equilibrium swollen gels), hysteresis and with decreases in the degree of swelling, broadening of the phase transition region, and a decrease in elastic recovery at high deformations. The presence of linear PVP in the networks increases porosity and the pore size, increases swelling, deswelling rates, and hysteresis, but decreases slightly lower critical solution temperature (LCST), tensile strength, elongation, and elastic recovery. The strongest hydrogels were ones with 10 wt % PNIPA and 5 wt % of nanoclays, displaying tensile strengths of 85 kPa and elongation of 955%. All properties of hydrogels at the equilibrium swollen state are lower than in the as‐prepared state, due to the lower concentration of chains per unit volume, but the trends are preserved. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

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