Ferroelectric-Paraelectric Transition In A Membrane With Quenched-Induced δ-Phase Of PVDF.

The stabilization of δ-phase of poly(vinylidene fluoride) PVDF in a 14 µm-thickness ferroelectric membrane is achieved by a simple route based on the use of a dimethylformamide (DMF)/acetone solvent, in which the application of external electric field is not required. X-ray diffraction and calorimetric experiments on heating reveal that, at 154 °C, the original mixture between ferroelectric δ-phase and paraelectric α-phase transits to a system with only this latter phase in the crystalline fraction. A gradual and slight increment of amorphous fraction up to the melting at 161 °C is also observed. The existence of δ-phase is corroborated by the occurrence of a broad maximum around 154 °C in dielectric permittivity measurements, as well as the hysteresis loops observed at room temperature. These results suggest a wide thermal window for a stable δ-phase, between room temperature and 154 °C, a subsequent transition into α-phase and the corresponding melting at 161 °C. The broad dielectric maximum observed around 154 °C in dielectric and calorimetric measurements, can be associated with a diffuse ferroelectric-paraelectric transition.

Development of meniscus substitutes using a mixture of biocompatible polymers and extra cellular matrix components by electrospinning.

Despite the significant advances in the meniscus tissue engineering field, it is difficult to recreate the complex structure and organization of the collagenous matrix of the meniscus. In this work, we developed a meniscus prototype to be used as substitute or scaffold for the regeneration of the meniscal matrix, recreating the differential morphology of the meniscus by electrospinning. Synthetic biocompatible polymers were combined with the extracellular matrix component, collagen and used to replicate the meniscus. We studied the correlation between mechanical and structural properties of the polymer blend as a function of collagen concentration. Fibers were collected on a surface of a rapidly rotating precast mold, to accurately replicate each sectional morphology of the meniscus; different electro-tissues were produced. Detailed XRD analyses exhibited structural changes developed by electrospinning. We achieved to integrate all these electro-tissues to form a complete synthetic meniscus. Vascularization tests were performed to assess the potential use of our novel polymeric blend for promising meniscus regeneration.