Thermally Induced Polymorphic Changes in Poly(Vinylidene Fluoride) Thin Layer Investigated Using Micro-Raman Spectroscopy

We present the results on evolution thermally induced polymorphic changes of PVDF and the PVDF-ZnO composite layers investigated in-situ using an experimental set-up consisting of a high resolution micro-Raman spectrometer (LabRAM HR 800, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\lambda=632.8nm$</tex>) and a thermoelectric cell (DSC600) with optical access to the sample. Three types of sample-PVDF pure layer, PVDF: ZnO nanoparticles(NPs) and PVDF: ZnO nanorods(NRs) were subjected to stress by heating at different temperature from 50°C close to melting temperature, 170 °C. ZnO NPs and NRs added in PVDF leads to obtaining a PVDF nanocomposite in which the intensity of the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta$</tex> phase is much higher than that of the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\alpha$</tex> phase, intensities ratio <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$I_{\beta}(839.5cm^{-1}) /I_{\alpha}(798.5cm^{-1})&gt;5.56$</tex>. The phase is stable up to 150 °C and with the increase in temperature to 170°C, the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta$</tex> phase passes to a lower crystallinity a phase with a large amorphous content highlighted by region 400–700 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> and and 800–1000 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> without Raman peaks.