Carlo Boaretti

Electrically Conductive Membranes Obtained by Simultaneous Electrospinning and Electrospraying Processes

Electrically conductive polyurethane nanostructured membranes have been prepared combining the electrospinning of polymer nanofibers NFs with the electrospraying of pristine multiwall carbon nanotubes MWCNTs in simultaneous processes. In order to have a better understanding of the distribution of MWCNTs on the surface of the membranes, the optimization of the electrospraying process has been carried out and the distribution of MWCNTs has been evaluated using image texture analysis techniques. Large membranes with a volume resistivity typical of electrostatic discharge materials with a MWCNTs concentration less than 0.3% wt 0.01 mg/cm2 have been obtained and characterized with morphological SEM and TEM and spectroscopic UV-Vis, Raman techniques.

Synthesis and Process Optimization of Electrospun PEEK-Sulfonated Nanofibers by Response Surface Methodology

In this study electrospun nanofibers of partially sulfonated polyether ether ketone have been produced as a preliminary step for a possible development of composite proton exchange membranes for fuel cells. Response surface methodology has been employed for the modelling and optimization of the electrospinning process, using a Box-Behnken design. The investigation, based on a second order polynomial model, has been focused on the analysis of the effect of both process (voltage, tip-to-collector distance, flow rate) and material (sulfonation degree) variables on the mean fiber diameter. The final model has been verified by a series of statistical tests on the residuals and validated by a comparison procedure of samples at different sulfonation degrees, realized according to optimized conditions, for the production of homogeneous thin nanofibers.

Electrospun Nanofibrous Membranes

Membranes comprised of randomly oriented fibers ranging from microns to nanometers in diameter combine small pore size with high porosity. This porous structure has been shown to improve performance in many applications including filtration, catalysis, sensing and tissue engineering. The open porous structure of nanofiber membranes plays an essential role in enhancing the performance of the nanofiber-based materials in these applications. The porous structure of nanofiber membranes is also a determining factor in biological sensors, which require wicking of liquid analytes through the membrane to the detection point. The usage of electrospun nanofibrous scaffolds for biomedical applications has attracted a great deal of attention in the past several years. For examples, nanofibrous scaffolds have been demonstrated as suitable substrates for tissue engineering, immobilized enzymes and catalyst, wound dressing and artificial blood vessels. They have also been used as barriers for the prevention of postoperative induced adhesion and vehicles for controlled drug delivery [1]. For example, tumortargeting nano-scale carrier from electrospun PLGA membranes through surface modification can convey the radio-active nuclide quantitatively to the tumor tissue by directly embedded at the lesions and can also play an anti-adhesion function at where surgical procedures have been made [2]. Nanofiber membranes are ideal for this application because the highly porous network of interconnected pores provides the necessary pathways for transport of oxygen and nutrients that are crucial for cellular growth, and tissue regeneration [3].

Microwave-assisted synthesis of isosorbide-derived diols for the preparation of thermally stable thermoplastic polyurethane

Abstract In order to prepare thermally stable isosorbide-derived thermoplastic polyurethane, the synthesis of two new chiral exo–exo configured diols, prepared from isosorbide, and two types of diphenols (bisphenol A and thiodiphenol) was described. The synthesis conditions were optimized under conventional heating and microwave irradiations. To prove their suitability in polymerization, these monomers were successfully polymerized using 4,4′-diphenylmethane diisocyanate (MDI) and hexamethylene diisocyanate (HDI). Both monomers and polymers have been studied by NMR, FT-IR, TGA, DSC; intrinsic viscosity of polymers has also been determined. The results showed the effectiveness of the synthetic strategy proposed; moreover, a dramatic reduction of the reaction time and an important improvement of the monomers yield using microwave irradiation have been demonstrated. The monomers, as well as the polymers, showed excellent thermal stability both in air and nitrogen. It was also shown that the introduction of sulphur in the polyurethane backbone was effective in delaying the onset of degradation as well as the degradation rate.