Heterogeneous hydrogels were prepared by gamma-ray irradiation of aqueous solutions of N-isopropylacrylamide ( NIPAAm) and acrylic acid (AAc) having various compositions above the lower critical solution temperature. The structures of the poly(N-isopropylacrylamide) ( PNIPAAm) gel and poly(NIP-AAm-co-AAc) gels in both their highly hydrated and their natural states were observed by environmental scanning electron microscopy. The heterogeneous structures of the homopolymer gel and the copolymer gels whose AAc contents were between 10 - 50% consisted of interconnected microspheres. In the copolymer gel with a high AAc content, the structure became a largely interconnected one which lacked micro-droplets. The hydrophobic interaction caused by hydrogen bonding between the unionized carboxylic acid groups of AAc and the amide groups of NIPAAm, the rates of polymerization, and the aggregation rates play important roles in the formation of interconnected microsphere gel structures.
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- DOI : 10.1007/s00396-004-1103-6
- ISSN : 0303-402X
- CiNii Articles ID : 80017064149
- Web of Science ID : WOS:000225305000003