The “thio-click” polymerization is a well-expanded concept of click polymerization. Among the click polymerizations, the thiol–yne click polymerization is less developed and still in its infancy stage. In general, UV light, elevated temperature, amine, or transition metal complexes is needed to catalyze the thiol–yne click polymerization, which greatly complicates the experimental operation and limits its application. In this work, a facile and powerful thiol–yne click polymerization was developed, which could be carried out under very mild conditions without using external catalyst. Simply mixing the aromatic diynes (1a–1e) and dithiols (2–4) with equivalent molar ratio in THF at 30 °C will readily produce soluble and regioregular functional poly(vinylene sulfide)s (PIa–PIe, PII, and PIII) with high molecular weights (Mw up to 85 200) in excellent yields (up to 97%) after as short as 2 h. Furthermore, no double addition product of an ethynyl group was found. This catalyst-free thiol–yne click polymerizat...

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Catalyst-Free Thiol−Yne Click Polymerization: A Powerful and Facile Tool for Preparation of Functional Poly(vinylene sulfide)s

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. Over the years and thanks to the advances in the synthesis of truxene derivatives, the scope of applications of this attractive building block, initially limited to synthesis and photoluminescence, has nowadays been extended to organic electronics. This review aims at highlighting the benefits brought by the introduction of this rigid star-shaped molecule in different materials. Perspectives for this highly appealing molecule in future research will also be put forth.

Truxene: a promising scaffold for future materials

The metal-free click polymerization (MFCP) of azide and alkyne has become a powerful tool for the synthesis of functional polytriazoles. Among which, the MFCP of propiolate and azide has been used to prepare functional linear poly(aroxycarbonyltriazole)s (PACTs). Their hyperbranched analogues, however, have been rarely prepared. In this paper, hyperbranched PACTs with satisfactory molecular weights and high regioregularities were synthesized in high yields by the MFCP of tripropiolates (1) and tetraphenylethene (TPE)-containing diazide (2) under the optimized reaction conditions without protection from oxygen and moisture. The resultant polymers are soluble in common organic solvents and thermally stable, with 5% loss of their weights at temperatures higher than 330 °C. The polymers exhibit high refractive indices with low chromatic dispersion. Thanks to their contained TPE units, the polymers show the unique feature of aggregation-induced emission, and their aggregates can function as fluorescent sensors...

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Hyperbranched Poly(aroxycarbonyltriazole)s: Metal-Free Click Polymerization, Light Refraction, Aggregation-Induced Emission, Explosive Detection, and Fluorescent Patterning

Cu(I)-catalyzed azide–alkyne click polymerization, developed based on the click reaction, has become a powerful tool for the construction of functional polytriazoles with linear and hyperbranched structures. This method has, however, rarely been used for the preparation of functional hyperbranched conjugated polytriazoles (hb-CPTA). In this paper, soluble ethynyl-capped hb-CPTA with weight-averaged molecular weight of 39 500 was synthesized in high yield (84.4%) by the Cu(I)-catalyzed azide–alkyne click polymerization of tetraphenylethene containing diazide [1,2-bis(4-azidophenyl)-1,2-diphenylethene] and tetrayne [1,1,2,2-tetrakis(4-ethynylphenyl)ethane] in equal concentration. By taking advantage of the ethynyl groups on its periphery, the polymer could be efficiently postfunctionalized by azide–alkyne and thiol–yne click reactions. The polymers are thermally stable and loss 5% of their weights at temperatures higher than 340.0 °C. hb-CPTA also possesses high char yield (74.8%) at 800 °C. The polymers fe...

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Ethynyl-Capped Hyperbranched Conjugated Polytriazole: Click Polymerization, Clickable Modification, and Aggregation-Enhanced Emission

The Cu(I)-catalyzed azide-alkyne click polymerization is well developed and broadly applied to the preparation of functional polymers. The removal of copper residues from the resultant polymers is, however, difficult. One way to completely circumvent this difficulty is to develop click polymerization without the use of metallic catalysts, i.e., metal-free click polymerization (MFCP). Herein, recent efforts towards developing MFCP of activated alkynes and azides, and of activated azides and alkynes, to produce regioregular polytriazoles are summarized, and the properties and applications of the resultant polymers are also briefly discussed.

Regioselective Metal-Free Click Polymerization of Azides and Alkynes

It has been a challenge to synthesize high molecular weight and soluble conjugated hyperbranched poly(1,2,3-triazole)s (hb-PTAs). In this paper a series of soluble hyperbranched polytriazoles, whose number-average molecular weight (Mn) and polydispersity index ranged in (1.2–3.3)×104 and 1.7–3.0, respectively, were synthesized with A2+B3 approach. In the polymerization process, diazides A1–A4 and triyne B1 were used as A2 and B3 monomers; Cu(I)-catalyst, THF and water were used as their reaction system. At room temperature the final molecular weight could be controlled through reaction time, so finally we obtained soluble conjugated hyperbranched poly(1,2,3-triazole)s hb-PTAs (1–4). The polymers were soluble in common organic solvents, and all emitted blue light; the films of polymers emitted yellow and blue light, due to the difference in the aggregation of their chromophoric units in the solid state. The thermal properties of the final copolymers were analyzed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

Aiqing Wang

Papers

Synthesis of Conjugated Hyperbranched Polytriazoles Containing Truxene Units by Click Polymerization