Surface Morphology at the Microscopic Scale, Swelling/Deswelling, and the Magnetic Properties of PNIPAM/CMC and PNIPAM/CMC/Fe₃O₄ Hydrogels

Marianna Uva; Andrea Atrei

doi:10.3390/gels2040030

Surface Morphology at the Microscopic Scale, Swelling/Deswelling, and the Magnetic Properties of PNIPAM/CMC and PNIPAM/CMC/Fe₃O₄ Hydrogels

Gels. 2016 Dec 13;2(4):30. doi: 10.3390/gels2040030.

Authors

Marianna Uva^{1

2}, Andrea Atrei^{3

4}

Affiliations

¹ Dipartimento di Biotecnologie, Chimica e Farmacia, Università di Siena, Via A. Moro 2, 53100 Siena, Italy. marianna.uva@unisi.it.
² CRISMA, Via. Matteotti 15 Colle di Val d'Elsa, 53034 Siena, Italy. marianna.uva@unisi.it.
³ Dipartimento di Biotecnologie, Chimica e Farmacia, Università di Siena, Via A. Moro 2, 53100 Siena, Italy. andrea.atrei@unisi.it.
⁴ CRISMA, Via. Matteotti 15 Colle di Val d'Elsa, 53034 Siena, Italy. andrea.atrei@unisi.it.

Abstract

Poly(N-isopropylacrylamide) (PNIPAM) hydrogels containing carboxymethylcellulose (CMC) and CMC/Fe₃O₄ nanoparticles were prepared. Free-radical polymerization with BIS as cross-linker was used to synthesize the hydrogels. The morphology at the microscopic scale of these materials was investigated using field emission scanning electron microscopy (FESEM). The images show that CMC in the PNIPAM hydrogels induces the formation of a honeycomb structure. This surface morphology was not observed for pure PNIPAM hydrogels prepared under similar conditions. The equilibrium swelling degree of the PNIPAM/CMC hydrogels (5200%) is much larger than that of the pure PNIPAM hydrogels (2500%). The water retention of PNIPAM/CMC hydrogels above the volume phase transition temperature is strongly reduced compared to that of pure PNIPAM hydrogel. Both PNIPAM/Fe₃O₄ and PNIPAM/CMC/Fe₃O₄ hydrogels exhibit a superparamagnetic behavior, but the blocking temperature (104 K) of the former is higher than that of the latter (83 K).

Keywords: field emission scanning electron microscopy (FESEM); hydrogels; magnetic nanoparticles; poly(N-isopropylacrylamide) (PNIPAM); thermoresponsive materials.