Attenuated Fourier Transform Infrared Spectroscopy Research Articles

Synthesis and microstructure–mechanical property relationships of segmented polyurethanes based on a PCL–PTHF–PCL block copolymer as soft segment

The goal of this work has been the synthesis of novel materials based on a biodegradable polycaprolactone-block–polytetrahydrofurane-block–polycaprolactone diol (PCL-b–PTHF-b–PCL). The segmented thermoplastic polyurethanes (STPU) have been synthesised in bulk without catalyst at different molar ratios and their characterization has been performed by different techniques. The physic-chemical interactions, responsible for the unique polyurethane properties, have been evaluated by total attenuated Fourier transform infrared spectroscopy (ATR-IR) in the amide I region using a Gaussian deconvolution technique and, on the other hand, atomic force microscopy (AFM) has been employed to determine the phase microstructures. The effect of increase the hard segment content (HS) has been discussed from the viewpoint of the miscibility of hard and soft segments, analyzed by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). The influence of HS content on the microstructure–mechanical property relationships has also been investigated. Special attention has been focused on the wettability of the samples, measured through water contact angle measurements (WCA), to determine the tendency for biocompatibility of the samples.

EFFECT OF GAS FLOW RATE ON CRYSTAL STRUCTURES OF ELECTROSPUN AND GAS-JET/ELECTROSPUN POLY(VINYLIDENE FLUORIDE) FIBERS

The effect of gas flow rate on crystal structures of electrospun and gas-jet/electrospun poly(vinylidene fluoride) (PVDF) fibers was investigated. PVDF fibers were prepared by electrospinning and gas-jet/electrospinning of its N,N-dimethylformamide (DMF) solutions. The morphology of the PVDF fibers was investigated by scanning electron microscopy (SEM). With an increase of the gas flow rate, the average diameters of PVDF fibers were decreased.The crystal structures and thermal properties of the PVDF fibers were investigated by attenuated Fourier transform infrared spectroscopy (AT-FTIR), wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). It was found that electrospinning and gas-jet/electrospinning of PVDF from its DMF solutions promoted the formation of β phase. Moreover, gas-jet/electrospun PVDF fibers exhibited higher crystallinity and β phase content than electrospun fibers did. Similar with electrostatic force, the drawing force of gas jet may induce the conformational change to all-trans (TTTT) planar zigzag conformation, and then promote the formation of the β phase.