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In this work, five 2‐ or 6‐ functionalized azulenes are electropolymerized to form azulene homopolymers. All five poly(azulenes) films exhibited electrochromism, with a two‐stage oxidation corresponding to the formation of the azulenium cation and the polaron, respectively. Electron‐donating groups at the 2‐position of azulene were found to greatly increase the poly(azulenes) film stability, with retention of optical contrast about four times as much as the 6‐alkylazulene analogue. This result demonstrates the potential of azulene functionalization as a strategy to improve the long‐term stability of electropolymerized azulenes, enabling applications in both optoelectronics as well as in ion selective electrodes. [ABSTRACT FROM AUTHOR]

Vinyl polymers have become ubiquitous products in our modern world, thanks to their exceptional strength, durability, and resistance to chemicals, all of which result from their highly stable all-carbon polymer backbone. However, this very stability raises concerns regarding their long-term persistence and environmental impact. To address this, researchers have explored the incorporation of stimuli-cleavable bonds as a potential solution. This approach allows vinyl polymers to retain their beneficial properties under normal conditions while readily degrading when exposed to specific stimuli, such as mechanical forces, light, redox reactions, pH changes, temperature shifts, and enzymatic activity. The chemical structures and mechanisms enabling stimuli responsiveness are discussed in this review. Beyond their environmental and recycling applications, stimuli-responsive degradable vinyl polymers have found diverse uses in fields like drug delivery systems, functional materials, and surface modification. This review also explores the latest advancements and novel applications for such polymers. Finally, the review discusses future research directions and design considerations to develop application-driven stimuli-cleavable vinyl polymers, aiming to unlock their full potential in addressing environmental concerns and fostering innovation across various industries. [ABSTRACT FROM AUTHOR]

Transition metal catalysed C−H bond activation chemistry has emerged as an exciting and promising approach in organic synthesis. This allows us to synthesize a wider range of functional molecules and conjugated polymers in a more convenient and more atom economical way. The formation of C−C bonds in the construction of pi‐conjugated systems, particularly for conjugated polymers, has benefited much from the advances in C−H bond activation chemistry. Compared to conventional transition‐metal catalysed cross‐coupling polymerization such as Suzuki and Stille cross‐coupling, pre‐functionalization of aromatic monomers, such as halogenation, borylation and stannylation, is no longer required for direct arylation polymerization (DArP), which involve C−H/C−X cross‐coupling, and oxidative direct arylation polymerization (Ox‐DArP), which involves C−H/C−H cross‐coupling protocols driven by the activation of monomers' C(sp2)−H bonds. Furthermore, poly(annulation) via C−H bond activation chemistry leads to the formation of unique pi‐conjugated moieties as part of the polymeric backbone. This review thus summarises advances to date in the synthesis of conjugated polymers utilizing transition metal catalysed C−H bond activation chemistry. A variety of conjugated polymers via DArP including poly(thiophene), thieno[3,4‐c]pyrrole‐4,6‐dione)‐containing, fluorenyl‐containing, benzothiadiazole‐containing and diketopyrrolopyrrole‐containing copolymers, were summarized. Conjugated polymers obtained through Ox‐DArP were outlined and compared. Furthermore, poly(annulation) using transition metal catalysed C−H bond activation chemistry was also reviewed. In the last part of this review, difficulties and perspective to make use of transition metal catalysed C−H activation polymerization to prepare conjugated polymers were discussed and commented. [ABSTRACT FROM AUTHOR]

Azulene, a unique isomer of naphthalene, has received much interest from researchers in different fields due to its unusual chemical structure with a negatively charged 5‐membered ring fused with a positively charged 7‐membered ring. In particular, incorporation of azulene into polymers has led to many interesting properties. This minireview covers functionalization methods of azulene at its various positions of 5‐ and 7‐membered rings to form azulene derivatives including azulene monomers, and gives an overview of a wide range of azulene‐containing polymers including poly(1,3‐azulene), azulene‐based copolymers with connectivity at 1,3‐positions of the 5‐membered ring, or 4,7‐positions of the 7‐membered ring, as well as copolymers with azulene units as side chains. Their chemical and physical properties together with applications of azulene‐containing polymers have also been summarized. [ABSTRACT FROM AUTHOR]

Thermochromic materials are substances that change colour in response to temperature variations. Today, sustainability concerns are the main drivers of thermochromic research, with smart, energy efficient windows being one of primary applications. While vanadium oxides and leuco dyes are traditionally the main thermochromic materials, hydrogels operating based on change of solvation have risen as some of the most promising materials due to their high optical transparency and good solar modulating abilities. In this work, a distinct mechanism for thermochromism arising from the crystalline solid to amorphous solid polymer transition, with a corresponding transition from an opaque state to a transparent state is disclosed. Both ultra-high optical transparency (T lum up to 99%) and ultra-high solar modulation (ΔT solar up to 87%) were observed. The transition temperature was tunable from 11 to 61 ͦ C by tuning the polymer structure. When incorporated into applications such as greenhouse materials and thermoelectric devices, significant performance enhancement was observed, due to the thermochromic material functioning as a thermal valve, speeding up solar heat absorbance while inhibiting the cooling process via its phase transition. This article is protected by copyright. All rights reserved., (This article is protected by copyright. All rights reserved.)

Hydrochromic materials, which change color in response to moisture, are highly sought-after due to some unique applications such as moisture detection, humidity monitoring, anti-counterfeiting, and sweat-pore mapping. We herein report a new thioxanthene-9-ols/thioxanthylium cations hydrochromic system. The hydrochromic thioxanthylium cations can be generated/regenerated by exposing a chemically stable thioxanthene-9-ol to trifluoroacetic acid (TFA). The intensely colored thioxanthylium cations can be chemically reverted to the colorless thioxanthene-9-ol. Interestingly, the conversion between thioxanthene-9-ol and its cation species was found to be highly reversible in most cases (up to 50 activation-deactivation cycles). The color and moisture-sensitivity of thioxanthylium cations were also validated to be tunable via functionalization of the thioxanthene core with different aliphatic and aromatic groups at its 9 or 2,7-positions. Finally, paper probes were prepared using solution-immersion and inkjet-printing techniques to demonstrate the system's potential applications in humidity sensing and anti-counterfeiting., (© 2022 Wiley-VCH GmbH.)