Macromolecular Rapid Communications, Vol.26, No.19, 1538-1541, 2005
Giant complex modulus reduction of kappa-carrageenan magnetic gels
Effects of magnetization on the complex modulus of kappa-carrageenan magnetic gels have been investigated. The magnetic gel was made of a natural polymer, kappa-carrageenan, and a ferromagnetic particle, barium ferrite. The complex modulus of the magnetic gel was investigated by dynamic viscoelastic measurements with a compressional strain. It was first observed that the magnetic gels showed giant storage modulus reduction;approximate to 10(7) Pa before and after magnetization. The reduction was nearly independent of the frequency, and it increased with increasing the volume fraction of the ferrite. The maximum reduction in the storage modulus reached 14.9 MPa which corresponds to 76.5% of the modulus before magnetization. It was also found that the change in the modulus was nearly independent of a magnetization direction. Magnetism and morphology of the magnetic gels were also presented.