Ionene copolymer electrolyte obtained from cyclo-addition of di-alkyne and di-azide monomers for solid-state smart glass windows

Copper-Free Synthesis of Cationic Glycidyl Triazolyl Polymers

Copper-free synthesis of cationic glycidyl triazolyl polymers (GTPs) is achieved through a thermal azide-alkyne cycloaddition reaction between glycidyl azide polymer and propiolic acid, followed by decarboxylation and quaternization of the triazole unit. For synthesizing nonfunctionalized GTP (GTP-H), a microwave-assisted method enhances the decarboxylation reaction of carboxy-functionalized GTP (GTP-COOH). Three variants of cationic GTPs with different N-substituents [N-ethyl, N-butyl, and N-tri(ethylene glycol) monomethyl ether (EG3)] are synthesized. The molecular weight of GTP-H is determined via size exclusion chromatography. Thermal properties of all GTPs are characterized using differential scanning calorimetry and thermogravimetric analysis. The ionic conductivities of these cationic GTPs are assessed by impedance measurements. The conducting ion concentration and mobility are calculated based on the electrode polarization model. Among three cationic GTPs, the GTP with the N-EG3 substituent exhibits the highest ionic conductivity, reaching 6.8 × 10-6 S cm-1 at 25 °C under dry conditions. When compared to previously reported reference polymers, the reduction of steric crowding around the triazolium unit is considered to be a key factor in enhancing ionic conductivity.

1,3,4,5-Tetrasubstituted Poly(1,2,3-triazolium) Obtained through Metal-Free AA+BB Polyaddition of a Diazide and an Activated Internal Dialkyne

A tetra(ethylene glycol)-based 1,3,4,5-tetrasubstituted poly(1,2,3-triazolium) is synthesized in two steps including: i) the catalyst-free polyaddition of a diazide and an activated internal dialkyne and ii) the N-alkylation of the resulting 1,2,3-triazole groups. In order to provide detailed structure/properties correlations different analogs are also synthesized. First, parent poly(1,2,3-triazole)s are obtained via AA+BB polyaddition using copper(I)-catalyzed alkyne-azide cycloaddition or metal-free thermal alkyne-azide cycloaddition (TAAC). Poly(1,2,3-triazole)s with higher molar masses are obtained in higher yields by TAAC polyaddition. A 1,3,4-trisubstituted poly(1,2,3-triazolium) structural analog obtained by TAAC polyaddition using a terminal activated dialkyne and subsequent N-alkylation of the 1,2,3-triazole groups enables discussing the influence of the methyl group in the C-4 or C-5 position on thermal and ion conducting properties. Obtained polymers are characterized by 1H, 13C, and 19F NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis, size exclusion chromatography, and broadband dielectric spectroscopy. The targeted 1,3,4,5-tetrasubstituted poly(1,2,3-triazolium) exhibits a glass transition temperature of -23 °C and a direct current ionic conductivity of 2.0 × 10-6 S cm-1 at 30 °C under anhydrous conditions. The developed strategy offers opportunities to further tune the electron delocalization of the 1,2,3-triazolium cation and the properties of poly(1,2,3-triazolium)s using this additional substituent as structural handle.

Azo-Functionalized Thermoplastic Polyurethane for Light-Driven Shape Memory Materials

Shape memory polymers have great potential in the fields of soft robotics, injectable medical devices, and as essential materials for advanced electronic devices. Herein, light-triggered shape-memory thermoplastic polyurethane (TPU) is reported using azido TPU grafted by the photoswitchable azo compound. The trans-cis transitions of the azobenzene on the side chain of the TPU induce the recoiling of the main chain, leading to shaping memory behavior. Under UV irradiation, cis-azo allows the oriented main chain to recoil to release residual stress and realize light-triggered shape memory behavior. The facile method proposed here for the preparation of azo-functionalized TPU can provide viable opportunities for soft robotics and smart TPU applications.

Application of New Energy Thermochromic Composite Thermosensitive Materials of Smart Windows in Recent Years

Thermochromic smart windows technology can intelligently regulate indoor solar radiation by changing indoor light transmittance in response to thermal stimulation, thus reducing energy consumption of the building. In recent years, with the development of new energy-saving materials and the combination with practical technology, energy-saving smart windows technology has received more and more attention from scientific research. Based on the summary of thermochromic smart windows by Yi Long research groups, this review described the applications of thermal responsive organic materials in smart windows, including poly(N-isopropylacrylamide) (PNIPAm) hydrogels, hydroxypropyl cellulose (HPC) hydrogels, ionic liquids and liquid crystals. Besides, the mechanism of various organic materials and the properties of functional materials were also introduced. Finally, opportunities and challenges relating to thermochromic smart windows and prospects for future development are discussed.

Engineered Ionene/PNIPAM Hybrid Dual-Response Material Generating Tunable and Unique Optical Modes for Adaptive Solar Transmittance Modulation

A hybrid smart window exhibiting dual chromic response properties based on an ionene/polymer material is successfully engineered. Thermochromic poly(N-isopropylacrylamide) is integrated with an electrochromic viologen-tethered ionene, also acting as an electrolyte, to produce a smart window that can adaptively control solar visible light transmittance in response to multiple stimuli. This new blend allows the formation of unique reversible optical states, namely, "clear", "amber", "cloudy", and "grainy" states, which are passively triggered by environmental temperature and actively induced by external potential or simultaneously by both. This hybrid material shows tunability in terms of its electrochemical and optical properties, switching kinetics, and coloration efficiency and can also achieve a nearly absolute zero-transmissive state. With the material's excellent solubility and film-forming ability, the smart device can be fabricated with much flexibility and ease. Finally, this device has an all-in-one layer configuration, creating a more compact and simplified design. With all these properties combined, the development of a next-generation multifunctional smart window device, which can efficiently control incoming solar light for energy-saving in buildings and also provide visual comfort, is possible.

Effects of repeat unit charge density on the physical and electrochemical properties of novel heterocationic poly(ionic liquid)s

The higher the charge density of PILs the higher their T_g and the lower their conductivity; the best conductivity (1.8 × 10⁻⁵ S cm⁻¹ at 25 °C): PILs with triazolium cations; the best cathodic stability (−0.4 V vs. Li⁺/Li at 70 °C): PILs with mixed type cations.