Solid-state 13C NMR spectroscopic study of supercritical CO2 catalyzation treated polyethylene terephthalate textiles for platinum metallization

Abstract

In this study, polyethylene terephthalate (PET) textiles were metallized with Pt via supercritical carbon dioxide (sc-CO2) catalyzation, using palladium(II) hexafluoroacetylacetonate (Pd(hfac)2) as the Pd catalyst source. The effects of the treatments on the structural changes and molecular mobility of PET were elucidated by solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. The carbonyl and nonprotonated aromatic carbons and the methylene and protonated aromatic carbons were analyzed from the NMR spectra using a three-component model (crystalline, rigid amorphous, and mobile amorphous components), which inferred that the PET polymer textile comprised one crystalline and two amorphous regions. Additionally, when Pd catalyzation was performed on the textile under sc-CO2 conditions, the crystalline peak of the carbonyl carbon exhibited a chemical shift into a higher magnetic field, and the spin–lattice relaxation time increased. These results implied that Pd could exist in the vicinity of the CO carbon. The X-ray diffraction studies also showed crystallinity of PET increased by sc-CO2 catalyzation, while sc-CO2 annealing without Pd(hfac)2 did not increase it. Therefore, Pt films were successfully coated on the PET via catalytic plating using sc-CO2. The catalyzation reduced the molecular mobility of the PET polymer, indicating the incorporation of the catalytic metal into the polymer chain. The carbonyl carbon peak simultaneously shifted to a higher field, implying that the catalytic Pd could approach the carbonyl groups. The detailed analysis of the structure and molecular mobility provides valuable information that can contribute to the development of novel conductive materials.