Synthesis of Conjugated Hyperbranched Polytriazoles Containing Truxene Units by Click Polymerization

Construction of Functional Hyperbranched Poly(phenyltriazolylcarboxylate)s by Metal-Free Phenylpropiolate-Azide Polycycloaddition

The 1,3-dipolar cycloaddition of activated internal alkynes with azides has been developed into an efficient polymerization reaction for constructing functional linear 1,4,5-trisubstitued polytriazoles. However, it is rarely employed for the synthesis of hyperbranched polymers. In this work, metal-free polycycloadditions of tris(3-phenylpropiolate)s (1) and tetraphenylethene-containing diazides (2) are performed in dimethylformamide at 100 °C for 7 and 12 h, producing hyperbranched poly(phenyltriazolylcarboxylate)s (hb-PPTCs) with high molecular weights and satisfactory regioregularities in good yields. The hb-PPTCs have good solubility in common organic solvents and high thermal stability. They are non-emissive in solutions, but emit intensively upon aggregation, showing an aggregation-induced emission effect. Their aggregates can work as fluorescent sensors for explosive detection with high sensitivity. Furthermore, the polymers can be utilized for the fabrication of 2D fluorescent patterns with high resolution by UV irradiation through copper grid masks.

Synthesis of Nitrogen-Rich Polymers by Click Polymerization Reaction and Gas Sorption Property

Microporous organic polymers (MOPs) are promising materials for gas sorption because of their intrinsic and permanent porosity, designable framework, and low density. The introduction of nitrogen-rich building block in MOPs will greatly enhance the gas sorption capacity. Here, we report the synthesis of MOPs from the 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine unit and aromatic azides linkers by click polymerization reaction. Fourier transform infrared (FTIR) and solid-state 13C CP-MAS (Cross Polarization-Magic Angle Spinning) NMR confirm the formation of the polymers. CMOP-1 and CMOP-2 exhibit microporous networks with a BET (Brunauer⁻Emmett⁻Teller) surface area of 431 m²·g-1 and 406 m²·g-1 and a narrow pore size distribution under 1.2 nm. Gas sorption isotherms including CO₂ and H₂ were measured. CMOP-1 stores a superior CO₂ level of 1.85 mmol·g-1 at 273 K/1.0 bar, and an H₂ uptake of up to 2.94 mmol·g-1 at 77 K/1.0 bar, while CMOP-2, with its smaller surface area, shows a lower CO₂ adsorption capacity of 1.64 mmol·g-1 and an H₂ uptake of 2.48 mmol·g-1. In addition, I₂ vapor adsorption was tested at 353 K. CMOP-1 shows a higher gravimetric load of 160 wt%. Despite the moderate surface area, the CMOPs display excellent sorption ability for CO₂ and I₂ due to the nitrogen-rich content in the polymers.

Rendering cross-conjugated azophenine derivatives emissive to probe the silent photophysical properties of emeraldine

An azophenine derivative was synthesized by coupling truxene and azophenine via the copper-free Sonagashira reaction using Pd₂(dba)₃ and As(PPh)₃ as catalysts. The crystal structure of this heavy azophenine model (∼4000) was made and the identity of the structure was confirmed. By introducing truxene groups into this cross-conjugated structure, the deactivating rotations around the NH-C₆H₄ bonds were slowed down, which rendered this derivative near-IR emissive at 298 K. This species provided then the appropriate spectral and kinetic signatures for knowing where and what to look for in emeraldine, which was called non-emissive. Besides, two other compounds were also synthesized as models for this azophenine derivative for comparison and interpretation purposes.

Novel hyperbranched poly(urethane–imide)s with enhanced thermal, mechanical, and UV-shielding properties

A series of novel hyperbranched poly(urethane–imide)s (HBPUIs) was synthesized and derived from as-prepared imide-containing glycol and commercial materials via an A2 + B2 + B3 approach. The chemical and morphological structures of the resulting polymers were evaluated by infrared attenuated total reflection and X-ray diffraction techniques, respectively. Compared with pure HBPU, HBPUIs exhibited better thermal stability with the 10% weight loss temperature of 282–298°C under nitrogen atmosphere, good mechanical property with the tensile strength of 2–19 MPa, and elongation at breaks of 461–896%. Moreover, optical transmissivity of all films was measured and the results showed that they had excellent transparency in the scope of visible light. Meanwhile, the cutoff wavelengths of as-prepared HBPUI films were at around 350 nm, which can block the whole ultraviolet (UV)-C (200–280 nm) and UV-B (280–320 nm), as well as a part of UV-A (320–400 nm). Furthermore, the designed photocatalytic degradation experiment of the methylene blue (MB) confirmed that HBPUI films had good UV-shielding performance with 70% degradation of MB after intense UV irradiation (400 W) for 50 min under the protection of HBPUI film with 14% imide-containing glycol. This endowed HBPUIs with potential applications prospect in UV-shielding materials.

Hyperbranched conjugated polymers containing 1,3-butadiene units: metal-free catalyzed synthesis and selective chemosensors for Fe3+ ions

Hyperbranched polymers containing 1,3-butadiene units in main chain were synthesized by transition-metal-free catalysis and investigated as chemosensors for Fe³⁺ ions.

Cu(i)-Catalyzed amino-yne click polymerization

The first example of Cu(i)-catalyzed regio-specific and stereo-selective amino-yne click polymerization was established.

Truxene: a promising scaffold for future materials

Truxene (10,15-dihydro-5H-diindeno[1,2-a;1′,2′-c]fluorene), which is a heptacyclic polyarene structure, has attracted a great deal of interest due to its exceptional solubility, high thermal stability and ease with which it may be modified.

A recyclable and reusable supported Cu(I) catalyzed azide-alkyne click polymerization

The azide-alkyne click polymerization (AACP) has emerged as a powerful tool for the synthesis of functional polytriazoles. While, for the Cu(I)-catalyzed AACP, the removal of the catalytic Cu(I) species from the resulting polytriazoles is difficult, and the research on the recyclability and reusability of the catalyst remains intact. Herein, we reported the first example of using recyclable and reusable supported Cu(I) catalyst of CuI@A-21 for the AACP. CuI@A-21 could not only efficiently catalyze the AACP but also be reused for at least 4 cycles. Moreover, pronounced reduction of copper residues in the products was achieved. Apart from being a green and cost-effective polymer synthesis strategy, this method will also broaden the application of AACP in material and biological sciences and provide guidelines for other polymerizations with metal catalysts.

New insights into the initial stages of Ta oxide nanotube formation on polycrystalline Ta electrodes

Ta oxide nanotubes (NTs) were formed by the anodization of Ta at 15 V in a solution of concentrated sulfuric acid containing 0.8-1.0 M hydrofluoric acid. To study the initial stages of NT formation, FESEM images of samples anodized for very short times were obtained. The results contradict the existing explanation of the current-time data collected during anodization, which has persisted in the literature for more than two decades. In addition to providing a first-time morphological study of Ta oxide NT formation at very early stages of anodization, we also propose a new interpretation of the i-t response, showing that pores are already present in the first few milliseconds of anodization and that NTs are formed well before present models predict. This behaviour may also extend to the anodization of other valve metals, such as Al, Ti, Zr, W, and Nb.