Summary Stage I (2025)
In Stage I (2025) of the NIReCSD project, the reaction intermediates and three (3) phenoxazine-based (POZ) diamines were synthesized and characterized. The chemical structure of these new diamines, as well as of the intermediates, was confirmed by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and Fourier-transform infrared spectroscopy (FT–IR). Both proton and carbon NMR spectra confirmed the expected structures and a purity level of 99%. In the 1H NMR spectra, the diamines displayed characteristic signals corresponding to amino groups, as well as other aliphatic and aromatic structural features, clearly indicating the presence of POZ units. The amino groups were further confirmed in the 13C NMR spectra by the signal observed at 145 ppm. Additionally, the FT–IR spectra exhibited the characteristic absorption bands of the amino functional group. These newly synthesized diamines were used in Stage I for the preparation of aromatic polyamides that will be tested in prototype devices with electrocromic response in the near-infrared (NIR) region and with energy-storage capability. The polymers were synthesized via polycondensation reactions, yielding six (6) polyamides grouped into three series. The goal was to evaluate, on the one hand, the most advantageous polymer class in terms of physicochemical properties and electrocromic performance, and on the other hand, to identify the optimal reaction partners within the same class that would lead to the best overall performance. The chemical structures of the polymers were confirmed by proton NMR and FT–IR spectroscopy, through which the characteristic structural elements of each polymer class were identified. The thermal properties of the polymers were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The glass-transition temperatures fell within the expected range for aromatic polyamides. All polymers demonstrated very good thermal stability, as expected, with maximum decomposition temperatures between 411 and 422 °C. Thus, the results successfully meet the requirements for using these polymers as electroactive layers in EC devices operating in the NIR region and exhibiting energy-storage capability. The quality and morphology of the thin polymer films were examined by scanning electron microscopy (SEM), and the images showed smooth and homogeneous surfaces without cracks or voids. Ground- and excited-state geometries were obtained by DFT and TD-DFT calculations using the B3LYP functional and the 6-31+G(d,p) basis set, aiming to identify the distribution of HOMO, SOMO, and LUMO orbitals and the main transitions in the experimental UV–Vis–NIR spectra following oxidation. These calculations revealed π–π* transitions associated with polaronic entities located in the NIR region during the oxidation process. Upon anodic scanning, the polymers displayed three or four reversible redox couples. The first redox couple, associated with oxidation of the POZ unit, was evaluated in terms of electrochemical reversibility and stability, and the polymers showed excellent performance even after 500 repeated cycles. Spectroelectrochemical measurements revealed systematic changes in the absorption bands with increasing potential, associated with the formation of radical cations and di(poly)cationic species. These spectral changes were accompanied by visible color transitions in the films: light brown→violet→dark blue or light pink→pink. Stage I results were disseminated through 4 oral presentations at 4 international scientific events, 2 articles published in ISI-indexed journals (Q1 JCI, Q1 AIS), and 1 article submitted for publication (Q1 JCI, Q1 AIS, under review). Additionally, a dedicated project webpage was created on the host institution’s official website, providing high visibility and serving as a continuous dissemination tool throughout the project.
Proposed Results for Stage I
- 3 phenoxazine-based monomers
- 6 phenoxazine-based polymers
- project web page
- 4 participations in scientific events
- 2 articles published in Q1/Q2 (JCI – WoS) ISI-indexed journals
- scientific report on polymer characteristics and structure–property relationships
Achieved Results for Stage I
- 3 phenoxazine-based monomers
- 6 phenoxazine-based polymers
- project web page
- 4 participations in scientific events
- 2 articles published in Q1 (JCI – WoS) ISI-indexed journals
- 1 article submitted for publication in a Q1 (JCI – WoS) ISI-indexed journal
- scientific report on polymer characteristics and structure–property relationships |
