Spectroscopic investigations of PS-PVDF blends

Blends of polystyrene-polyvinylidene fluoride (PS-PVDF) have been obtained by melt mixing using a Haake mixer. Blends containing various compositions (0%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 75%, 85%, 90%, 95%, 99%, and 100% weight PS) were obtained using the following parameters for the four-step mixing (step 1 at 175 oC and 40 rotations per minute - RPM - for 5 minutes, step 2 at 190 oC and 60 RPM for 15 minutes, step 3 at 210 oC and 90 RPM for 30 minutes, and step 4 at 180 oC at 60 RPM for 15 minutes).
Blends of PS-PVDF have also been obtained by force spinning. The force spinning used solutions of PS-PVDF blends in dimethylformamide (DMF) of different concentrations and at various rotations (2500, 5000, and 7500 RPM, respectively).The as obtained mats or pellets have been investigated by Raman spectroscopy by using a Raman Renishaw confocal microscope operating at 532 and 785 nm, by UV-Vis spectroscopy using a Bruker Tensor 27/Hyperion system, and by X-Ray diffraction using a Bruker Discovery 8 spectrometer. Optical and electron microscopy were used to determine the average diameter of PS-PVDF nanofibers and the effect of concentration, composition (PS/PVDF), and spinning rate on the diameter of nanofibers. The effect of composition and manufacturing path on the contact angle (using distilled water as fluid) for both melted blends and mats has been analyzed in detail.
The research focuses on the identification of the phase composition of the blends and on the estimation of the ratio between the non ferroelectric phase of PVDF (alpha phase) and the ferroelectric phase(s) (beta and eventually gamma). The research aims to achieve mats and eventually blends of PS-PVDF with enhanced ferroelectric properties.