Characteristic role of crosslinker on thermally induced volumetric contraction–expansion processes in poly(N-isopropylacrylamide) networks and water systems
✍ Scribed by Tadashi Tokuhiro; Akira T. Tokuhiro
- Publisher
- John Wiley and Sons
- Year
- 2009
- Tongue
- English
- Weight
- 269 KB
- Volume
- 112
- Category
- Article
- ISSN
- 0021-8995
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✦ Synopsis
Abstract
In this work, the degree of crosslinking on the volumetric contraction–expansion processes of hydrogels made of poly(N‐isopropylacrylamide) (NIPA) (initial amount: C~m~) with varied amount (z) of crosslinking agent methylene‐bis‐acrylamide (BIS) in reference to most commonly used NIPA gel that was synthesized with C~m~ = 700 m__M__ and z = 8.6 m__M__ was investigated by applying our recently developed pycnometry. We focused on characteristic role of four polymeric NIPA residues directly bonded to a single BIS molecule by evaluating the total volume of gels per four NIPA residues directly bonded to a BIS molecule, plus associated water [ν~sp~(gel)(NIPA)~bonded~)(T)], and the corresponding number of water molecules per four NIPA residues [N~s~(gel)(NIPA)~bonded~)(T)]. We elucidated how these quantities characteristically contribute to changes in the volumetric contraction–expansion processes of hydrogels. A comparison of these quantities with the corresponding quantities for (NIPA)~unbonded~ residues clearly revealed a significant structural difference between (NIPA)~bonded~ and (NIPA)~unbonded~. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009