Characterization of polar groups in polyvinyl chloride–ethyl vinyl acetate blends using coincidence Doppler broadening spectroscopy

Abstract

Coincidence Doppler broadening spectroscopy (CDBS), known for its exceptional precision, is extensively employed in examining the electronic states of polymers. In this study, polyvinyl chloride (PVC)–ethyl vinyl acetate (EVA) polymers blends were prepared using conventional techniques, following specific ratios (75:25, 50:50, and 25:75, respectively). Spectroscopic analysis reveals that the longitudinal component of linear momentum surpasses the momentum unit (i.e., 10−3 m0c) when considering the ratio curve associated with the participation of oxygen core electrons. When compared to non‐polymer samples, the PVA polymer and PVA–EVA polymer blend exhibit greater free volume voids in contrast to non‐polymer structural defects. Furthermore, the annihilation of ortho‐positronium with core electrons, likely EVA oxygen core electrons, contributes to the measured free volume voids. An increased annihilation of positrons or positroniums by oxygen in the CDBS spectrum leads to higher calculated W parameter values. Conversely, as the PVC content increases, the W parameter decreases, suggesting reduced ortho‐positronium annihilation and consequently, enhanced formation of para‐positronium in the overall annihilation process. In summary, this investigation demonstrates the utility of CDBS in elucidating the electronic states and free volume voids in PVC and EVA polymers.