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The morphological structure of CB networks in elastomers and their flocculation dynamics under heat treatment and especially during vulcanization are analyzed by dynamic mechanical and dielectric spectroscopy. Dielectric spectra in the MHz range show that nanoscopic gaps between adjacent CB particles develop during heat treatment or vulcanization. These gaps are maintained by immobilized polymer layers acting as flexible bonds between the particles. Low‐frequency dielectric data indicate that the static percolation model qualitatively describes the dielectric properties of the conducting CB network on large length scales, but a superimposed kinetic aggregation process takes place on smaller length scales.

Upon irradiation with linearly polarized light a photoorientation process occurs in spincoated films of polymethacrylates with 4-hexyloxyazobenzene side groups containing para methoxy and trifluoromethoxy tail groups. It results in the induction of an oblate orientational distribution perpendicular to the electric field vector causing an optical in-plane anisotropy up to an order parameter of about 0.52. The annealing of the photoreoriented films above T g results in a prolate homeotropic alignment in the center of the irradiated spot up to a degree of order of 0.78, whereas an amplification of the photoinduced in-plane anisotropy is observed in the interim region to the nonirradiated film area. The development of the in-plane and the out-of-plane components is compared for the photoorientation and the subsequent photoreorientation process in this series of polymers. In both cases, the photogenerated order in the glassy state acts as an initializing force for the thermotropic self-organization resulting in a significant narrowing of an uniaxial orientational distribution. Thus, a photoinduced "command" effect in the bulk of the LC polymers is caused by the combination of both principles of orderingsthe photoorientation and the liquid crystallinity.

Hydrogels are used for 3D in vitro assays and tissue engineering and regeneration purposes. For a thorough interpretation of this technology, an integral biomechanical characterization of the materials is required. In this work, we characterize the mechanical and functional behavior of two specific hydrogels that play critical roles in wound healing, collagen and fibrin. A coherent and complementary characterization was performed using a generalized and standard composition of each hydrogel and a combination of techniques. Microstructural analysis was performed by scanning electron microscopy and confocal reflection imaging. Permeability was measured using a microfluidic-based experimental set-up, and mechanical responses were analyzed by rheology. We measured a pore size of 2.84 and 1.69 μm for collagen and fibrin, respectively. Correspondingly, the permeability of the gels was 1.00·10−12 and 5.73·10−13 m2. The shear modulus in the linear viscoelastic regime was 15 Pa for collagen and 300 Pa for fibrin. The gels exhibited strain-hardening behavior at ca. 10% and 50% strain for fibrin and collagen, respectively. This consistent biomechanical characterization provides a detailed and robust starting point for different 3D in vitro bioapplications, such as collagen and/or fibrin gels. These features may have major implications for 3D cellular behavior by inducing divergent microenvironmental cues.