Mechanisms, recent advancements and perspectives concerning nonconventional luminophores free of classic conjugates but with intrinsic photoluminescence are discussed.

take the superiorities in processability, biocompatibility, rich source, wide variety, and low cost. [7] Generally, achieving pure organic p-RTP follows two criteria: i) promotion of intersystem crossing (ISC) through aggregation [8] and introduction of carbonyl, heteroatoms, and heavy atoms; [7] ii) suppression of the nonradiative relaxation processes (vibration or external quenchers). [7,9] Specifically, for the latter, various approaches, including crystal engineering, [10] host-guest doping or complexation, [11] H-aggregation, [2a,3b,12] construction of metal-organic framework and perovskite hybrids, [13,14] and ionic or ionic-π interactions, [15] were centrally developed. Currently explored systems, however, are predominantly molecular organic crystals, whose amorphous states show weakened or even disappeared p-RTP, [16] thus hampering their practical applications. To overcome these drawbacks, amorphous (p-) RTP systems were developed, which generally create rigid environment through powerful intermolecular interactions. [11a,b,17-20] Nevertheless, the color tunability in a wide-range remains a daunting challenge. Therefore, further development of versatile platforms to realize distinct p-RTP emissions from blue to red is highly desired. [21] On the other hand, most of these p-RTP materials just show a single emission color, and only scattered examples demonstrating excitation-dependent [4] or time-dependent emissions [22] were reported. If the afterglow color can vary with time, it would empower the materials with rich encryption modes in security protection, thus promoting more reliable protection at much higher levels. [22] For example, Chi et al. reported the first example with time-dependent afterglow colors through weak intermolecular hydrogen-bonding interaction. [22a] And very recently, Yang and coworkers reported similar phenomenon that originates from well-separated thermally activated delayed fluorescence (TADF) and p-RTP with comparable but different lifetimes. [22b] Meanwhile, as an alternative to molecular p-RTP compounds, polymers are even more attractive on account of their film-forming ability, which is favorable for diverse technical applications with flexibility and ease processing procedures. [23] However, the development of a simple approach to fabricate amorphous polymers with color-tunable and multicolor p-RTP in response to excitation wavelength (λ ex), particularly those also accompanying time-dependent afterglows, remains highly challenging. Here we report such system based on sodium Achieving persistent room-temperature phosphorescence (p-RTP), particularly those of tunable full-colors, from pure organic amorphous polymers is attractive but challenging. Particularly, those with tunable multicolor p-RTP in response to excitation wavelength and time are highly important but both fundamentally and technically underexplored. Here, a facile and general strategy toward color-tunable p-RTP from blue to orange-red based on amidation grafting of luminophores onto sodium alginate (SA) chains...

Nonaromatic, cross‐conjugated, and highly twisted luminogens consisting of acylated succinimides demonstrate aggregation‐induced emission characteristics along with tunable multicolor photoluminescence and afterglows in their single crystals. Effective through‐space conjugation among different moieties bearing n/π electrons promote the spin–orbit coupling and intersystem crossing and lead to diverse emissive clusters with concurrently rigidified conformations, thus allowing readily tunable emissions. Derived from it, the proof‐of‐concept application for advanced anti‐counterfeiting is illustrated. These results should spur the rational design of novel nonaromatic AIEgens, and moreover advance understandings of the non‐traditional intrinsic luminescence and the origin of tunable multicolor afterglows.

An original design strategy for the preparation of polymers with a low dielectric constant is presented. The key to this design strategy is taking the most advantage of the secondary relaxation behavior of the polymer chains to obtain more free volume in the bulk, which can effectively reduce the dielectric constant of the polymer. By using this design strategy, we have successfully synthesized a novel polyimide TmBPHF with a pendant group that consists of a biphenyl unit attached to the meta-position of a phenyl ring that is part of a triaryl unit. The intrinsic k and dielectric loss values of the TmBPHF are 2.09 and 0.0012 at 10 kHz, respectively. More importantly, such outstanding low-k performance remains stable up to 300 °C. The excellent low-k performance of TmBPHF is mainly due to the secondary relaxation, especially the β relaxation, which occurs from the rotation of the pendant group. The TmBPHF film shows an ultralow moisture rate (∼0.17%), which is able to maintain the low-k property stability in different humid environments. Meanwhile, the TmBPHF film also shows excellent thermal stability and excellent mechanical properties, with a glass transition temperature (T g ) of 302 °C, 5 wt % decomposition temperature (T d5% ) of 549 °C, and residual of 70% at 800 °C under N 2 . The tensile strength and tensile modulus of the polyimide film are equal to 85.8 MPa and 2.02 GPa, respectively. In addition, the TmBPHF film is soluble in common solvents, which allows simple solution processing and efficient, low-cost, and continuous roll-to-roll processes. The design strategy is beneficial for lowering the k value and simultaneously maintaining the overall properties of polyimides, which possibly could also be extended to other novel high-performance polymer systems.

Pure organic room temperature phosphorescence (RTP) materials become increasingly important in advanced optoelectronic and bioelectronic applications. Current phosphors based on small aromatic molecules show emission characteristics generally limited to short wavelengths. It remains an enormous challenge to achieve red and near-infrared (NIR) RTP, particularly for those from nonaromatics. Here we demonstrate that succinimide derived cyclic imides can emit RTP in the red (665, 690 nm) and NIR (745 nm) spectral range with high efficiencies of up to 9.2%. Despite their rather limited molecular conjugations, their unique emission stems from the presence of the imide unit and heavy atoms, effective molecular clustering, and the electron delocalization of halogens. We further demonstrate that the presence of heavy atoms like halogen or chalcogen atoms in these systems is important to facilitate intersystem crossing as well as to extend through-space conjugation and to enable rigidified conformations. This universal strategy paves the way to the design of nonconventional luminophores with long wavelength emission and for emerging applications.