Total X‐Ray Illumination for Absolute Quantification of Crystalline Phases and Amorphous Content in PVDF and P(VDF‐TrFE)

ABSTRACT Fluoropolymers such as poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride‐co‐trifluoroethene) (P(VDF‐TrFE)) have numerous applications in electronic and mechanical devices, owing to their piezoelectric and ferroelectric properties. In these polymers, electromechanical coupling arises due to the consistent configuration of electropositive and electronegative atoms in certain crystalline phases, most notably the β phase, which has the highest net polarization. In order to examine the performance and optimize the processing parameters of a PVDF or P(VDF‐TrFE) specimen, it is important to accurately quantify the amounts of the different crystalline phases and the amorphous content in it. Here, we present a rigorous methodology to achieve this using X‐ray diffraction (XRD) and Rietveld refinement, which has several advantages over the currently popular approaches of Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). By introducing a sample weighting factor and Total Illumination by X‐rays (TIX) into the classic external standard method for amorphous fraction quantification, this analytical protocol addresses some quintessential challenges posed by organic materials, such as low X‐ray microabsorption and high amorphous content. This results in a framework applicable to diverse systems, including polymers, metal‐organic frameworks, and biological materials.