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1. Organic NIR Photodetectors: Pushing Photodiodes Beyond 1000 nm

   https://doi.org/10.21127/yaoyigc20200039  

   Rasmussen, Seth C.; Gilman, Spencer J.; Culver, Evan W.; Wilcox, Wyatt D. (June 2021, General chemistry)

   null (Ed.)

   Advances in the synthesis of low bandgap (Eg < 1.5 eV) conjugated polymers has produced organic materials capable of absorbing near-infrared (NIR) light (800—2500 nm), with these materials first applied to photodiode NIR detectors in 2007 as an alternative to more traditional inorganic devices. Although the development of organic NIR photodetectors has continued to advance, their ability to effectively detect wavelengths in the low-energy portion of the NIR spectrum is still limited. Efforts to date concerning the production of photodiode-based devices capable of detecting light beyond 1000 nm are reviewed. 

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2. Glass Transition Phenomenon for Conjugated Polymers

   https://doi.org/10.1002/macp.201900062  

   Qian, Zhiyuan; Cao, Zhiqiang; Galuska, Luke; Zhang, Song; Xu, Jie; Gu, Xiaodan (April 2019, Macromolecular Chemistry and Physics)

   Abstract Conjugated polymers are emerging as promising building blocks for a broad range of modern applications including skin‐like electronics, wearable optoelectronics, and sensory technologies. In the past three decades, the optical and electronic properties of conjugated polymers have been extensively studied, while their thermomechanical properties, especially the glass transition phenomenon which fundamentally represents the polymer chain dynamics, have received much less attention. Currently, there is a lack of design rules that underpin the glass transition temperature of these semirigid conjugated polymers, putting a constraint on the rational polymer design for flexible stretchable devices and stable polymer glass that is needed for the devices’ long‐term morphology stability. In this review article, the glass transition phenomenon for polymers, glass transition theories, and characterization techniques are first discussed. Then previous studies on the glass transition phenomenon of conjugated polymers are reviewed and a few empirical design rules are proposed to fine‐tune the glass transition temperature for conjugated polymers. The review paper is finished with perspectives on future directions on studying the glass transition phenomena of conjugated polymers. The goal of this perspective is to draw attention to challenges and opportunities of controlling, predicting, and designing polymeric semiconductors, specifically to accommodate their end use. 

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3. Rapid stress relaxation of high‐ T _g conjugated polymeric thin films

   https://doi.org/10.1002/pol.20230671  

   Ma, Guorong; Zhang, Song; Galuska, Luke_A; Gu, Xiaodan (November 2023, Journal of Polymer Science)

   Abstract Conjugated polymers consist of complex backbone structures and side‐chain moieties to meet various optoelectronic and processing requirements. Recent work on conjugated polymers has been devoted to studying the mechanical properties and developing new conjugated polymers with low modulus and high‐crack onset strain, while the thin film mechanical stability under long‐term external tensile strain is less investigated. Here we performed direct mechanical stress relaxation tests for both free‐standing and thin film floated on water surface on both high‐T_gand low‐T_gconjugated polymers, as well as a reference nonconjugated sample, polystyrene. We measured thin films with a range of film thickness from 38 to 179 nm to study the temperature and thickness effect on thin film relaxation, where an apparent enthalpy–entropy compensation effect for glassy polymer PS and PM6 thin films was observed. We also compared relaxation times across three different conjugated polymers and showed that both crystalline morphology and higher modulus reduce the relaxation rate besides higher glass transition temperature. Our work provides insights into the mechanical creep behavior of conjugated polymers, which will have an impact on the future design of stable functional organic electronics. 

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4. Benzobisthiadiazole-based high-spin donor–acceptor conjugated polymers with localized spin distribution

   https://doi.org/10.1039/D1MA00144B  

   Sabuj, Md Abdus; Huda, Md Masrul; Sarap, Chandra Shekar; Rai, Neeraj (May 2021, Materials Advances)

   null (Ed.)

   Stable organic semiconductors (OSCs) with a high-spin ground-state can profoundly impact emerging technologies such as organic magnetism, spintronics, and medical imaging. Over the last decade, there has been a significant effort to design π-conjugated materials with unpaired spin centers. Here, we report new donor–acceptor (D–A) conjugated polymers comprising cyclopentadithiophene and cyclopentadiselenophene donors with benzobisthiadiazole (BBT) and iso-BBT acceptors. Density functional theory calculations show that the BBT-based polymers display a decreasing singlet–triplet energy gap with increasing oligomer chain length, with degenerate singlet and triplet states for a N = 8 repeat unit. Furthermore, a considerable distance between the unpaired electrons with a pure diradical character disrupts the π-bond covalency and localizes the unpaired spins at the polymer ends. However, replacing the BBT acceptor with iso-BBT leads to a closed-shell configuration with a low-spin ground-state and a localized spin density on the polymer cores. This study shows the significance of the judicious choice of π-conjugated scaffolds in generating low- ( S = 0) and high-spin ( S = 1) ground-states in the neutral form, by modulation of spin topology in extended π-conjugated D–A polymers for emergent optoelectronic applications. 

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5. Unconventional Conjugated Polymers Derived from a Common Set of trans-Enediyne Monomers

   https://doi.org/10.1055/s-0036-1591939  

   Qin, Yang (April 2018, Synlett)

   This account describes our recent efforts in the design and synthesis of several series of unconventional conjugated polymers derived from a common set of trans-enediyne (tEDY) monomers. The journey started with a failed attempt, through acyclic diene metathesis of triene monomers, to prepare soluble polyacetylenes (PAs) having cross-conjugated side-groups on alternate double bonds along the main chain. At this seemingly dead end of the project, we found that the tEDY intermediates leading to triene monomers could undergo alkyne metathesis to generate soluble polydiacetylenes (PDAs). Such acyclic enediyne metathesis represents the first example of a solution synthesis of PDAs, in contrast to the conventional topochemical methods. By applying Glaser–Hay-type reaction conditions with selected tEDY monomers, polytriacetylenes were smoothly obtained; these possessed aromatic units directly attached to the polymer main chains, which significantly affected the electronic properties of the polymers. Furthermore, through hydroboration of the tEDY monomers, ‘boron-doped’ polyacetylenes (BDPAs) were prepared that can be considered as PAs with every fourth double bond replaced with a boron atom. These BDPAs represent the first boron main-chain conjugated polymers lacking aromatic units along the backbone, potentially enhancing electronic delocalization along the main chain. 

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