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<p>In this study, derivatives of polyvinyl alcohol (PVA) grafted with phthalic anhydride (PhA) and dyes were prepared to produce polymeric materials of PVA-g-PhA, PVA-g-PhA-anthocyanin, PVA-g-PhA-bromophenol blue, and PVA-g-PhA-thymol blue. The materials were characterised by FTIR and <sup>1</sup>H NMR spectroscopies. The crystallinity of the polymers was evaluated with powder X-ray diffraction, and the thermal stability by thermogravimetric analysis (TGA). The synthetic procedure for the polymeric materials entailed the formation of esters. The FTIR spectra of the polymers confirmed their formation since the ester carbonyl group stretch was observed at approximately 1691–1716&#xa0;cm<sup>−1</sup> in each material. NMR spectroscopy confirmed the addition of the dyes to the PVA-g-PhA backbone. All the powder X-ray diffractograms displayed the characteristic peak for PVA at a 2<i>θ</i> value of approximately 20°, as well as a small peak at 42° indicative of the semi-crystalline nature of the samples. These diffractograms indicate a small degree of crystallinity in a mainly bulk amorphous phase. Adding dyes to PVA-g-PhA improved the thermal stability of the resulting polymers. The PVA-g-PhA-bromophenol blue material was the most thermally stable. The absorption properties of PVA-g-PhA were extended into the visible region by the attachment of the dyes. The photostability of the polymers was investigated by irradiating them with 254&#xa0;nm light. The absorbance of the parent material, PVA-g-PhA, and the anthocyanin derivative increased with irradiation time until it reached a photostationary state. This increase in absorbance is attributed to the formation of more conjugated structures or light-absorbing photoproducts. On the other hand, the PVA-g-PhA-bromophenol blue and PVA-g-PhA-thymol blue materials photodegraded with increasing irradiation time. This research has shown that grafting dyes onto PVA can improve thermal stability and extend light absorption into the visible region. In particular, the addition of anthocyanin dye improved the photostability of the resulting material.</p>

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Preparation, Characterisation, and Photochemical Stability of Polymeric Derivatives of Polyvinyl Alcohol Grafted with Phthalic Anhydride and Dyes

  • 期刊论文

  • 发表日期：

    2025年3月8日

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  • Souad A. Mousa,
  • Sana Hitur Awad,
  • Bice S. Martincigh

摘要

In this study, derivatives of polyvinyl alcohol (PVA) grafted with phthalic anhydride (PhA) and dyes were prepared to produce polymeric materials of PVA-g-PhA, PVA-g-PhA-anthocyanin, PVA-g-PhA-bromophenol blue, and PVA-g-PhA-thymol blue. The materials were characterised by FTIR and 1H NMR spectroscopies. The crystallinity of the polymers was evaluated with powder X-ray diffraction, and the thermal stability by thermogravimetric analysis (TGA). The synthetic procedure for the polymeric materials entailed the formation of esters. The FTIR spectra of the polymers confirmed their formation since the ester carbonyl group stretch was observed at approximately 1691–1716 cm−1 in each material. NMR spectroscopy confirmed the addition of the dyes to the PVA-g-PhA backbone. All the powder X-ray diffractograms displayed the characteristic peak for PVA at a 2θ value of approximately 20°, as well as a small peak at 42° indicative of the semi-crystalline nature of the samples. These diffractograms indicate a small degree of crystallinity in a mainly bulk amorphous phase. Adding dyes to PVA-g-PhA improved the thermal stability of the resulting polymers. The PVA-g-PhA-bromophenol blue material was the most thermally stable. The absorption properties of PVA-g-PhA were extended into the visible region by the attachment of the dyes. The photostability of the polymers was investigated by irradiating them with 254 nm light. The absorbance of the parent material, PVA-g-PhA, and the anthocyanin derivative increased with irradiation time until it reached a photostationary state. This increase in absorbance is attributed to the formation of more conjugated structures or light-absorbing photoproducts. On the other hand, the PVA-g-PhA-bromophenol blue and PVA-g-PhA-thymol blue materials photodegraded with increasing irradiation time. This research has shown that grafting dyes onto PVA can improve thermal stability and extend light absorption into the visible region. In particular, the addition of anthocyanin dye improved the photostability of the resulting material.