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In this paper the magnetic field dependence of the resonant frequency, f res , and frequency of maximum absorption, f max , for a ferrofluid sample, for polarizing fields both perpendicular to and parallel with the axis of a coaxial cell, are presented for the first time.Measurements of the complex magnetic susceptibility,as a function of frequency, f (Hz), over the range 100 MHz-6 GHz and external polarizing field, H (kA m −1 ), up to approximately 100 kA m −1 , are obtained by means of the coaxial transmission line technique. The presence of ferromagnetic resonance in the ferrofluid, (at a frequency f res ) is found for all values of the polarizing field and the influence of demagnetizing effects on f res is accounted for. The dependence of f res on H is found to be linear and an average value of internal anisotropy field, H A , and the corresponding magnetic anisotropy constant,K, are determined.The susceptibility component profiles obtained for both cases of polarization are similar to those obtained in an analogous theoretical study of dielectrics subjected to an external electric field.

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Chitosan-g-oligolactide copolymers with relatively long oligolactide grafted chains of various stereochemical compositions have been synthetized via a solvent-free mechanochemical technique and tailored to fabricate three-dimensional hydrogels using two-photon induced microstereolithography. An effect of the characteristics of chitosan and oligolactide used for the synthesis on the grafting yield and copolymer’s behavior were evaluated using fractional analysis, FTIR-spectroscopy, dynamic light scattering, and UV-spectrophotometry. The lowest copolymer yield was found for the system based on chitosan with higher molecular weight, while the samples consisting of low-molecular weight chitosan showed higher grafting degrees, which were comparable in both the cases of l,l- or l,d-oligolactide grafting. The copolymer processability in the course of two-photon stereolithography was evaluated as a function of the copolymer’s characteristics and stereolithography conditions. The structure and mechanical properties of the model film samples and fabricated 3D hydrogels were studied using optical and scanning electron microscopy, as well as by using tensile and nanoindenter devices. The application of copolymer with oligo(l,d-lactide) side chains led to higher processability during two-photon stereolithography in terms of the response to the laser beam, reproduction of the digital model, and the mechanical properties of the fabricated hydrogels.