Constructing Strategy for Realizing White-Light-Emitting of Organic Aggregates Based on Self-Assembling Conjugated Polymer Nanobowls

The construction of single-component, white-light-emitting, conjugated polymers always utilizes fluorescence resonance energy transfer (FRET) for efficient emission. However, the main challenges in developing such materials primarily come from the effects of aggregation states during solution processing and the precise structural control required for the synthesis of compounds. Both aspects can affect the FRET between different lumophores in white-light-emitting materials. A novel supermolecular assembly strategy using new conjugated polymers (CPs) to fabricate single-component white-light-emitting CPs nanobowls (CPNBs) was developed to overcome the two difficulties. Specifically, through molecular structure engineering, side chains have been modified with a uracil group capable of hydrogen bonding, which stabilized the nanobowl structure during the supramolecular assembly process. Furthermore, by blending two kinds of CPs emitting different colors during the supramolecular assembly, single-component, white-light-emitting CPNBs have been achieved. The supramolecular strategy has resulted in stable and high-brightness, white-light emission, whether in aqueous solutions of different concentrations or in solid-state, polymer-based, composite materials. It also offers a more straightforward and environmentally friendly synthesis process for white-light-emitting organic materials.

Not All Aggregates Are Made the Same: Distinct Structures of Solution Aggregates Drastically Modulate Assembly Pathways, Morphology, and Electronic Properties of Conjugated Polymers

Tuning structures of solution-state aggregation and aggregation-mediated assembly pathways of conjugated polymers is crucial for optimizing their solid-state morphology and charge-transport property. However, it remains challenging to unravel and control the exact structures of solution aggregates, let alone to modulate assembly pathways in a controlled fashion. Herein, aggregate structures of an isoindigo-bithiophene-based polymer (PII-2T) are modulated by tuning selectivity of the solvent toward the side chain versus the backbone, which leads to three distinct assembly pathways: direct crystallization from side-chain-associated amorphous aggregates, chiral liquid crystal (LC)-mediated assembly from semicrystalline aggregates with side-chain and backbone stacking, and random agglomeration from backbone-stacked semicrystalline aggregates. Importantly, it is demonstrated that the amorphous solution aggregates, compared with semicrystalline ones, lead to significantly improved alignment and reduced paracrystalline disorder in the solid state due to direct crystallization during the meniscus-guided coating process. Alignment quantified by the dichroic ratio is enhanced by up to 14-fold, and the charge-carrier mobility increases by a maximum of 20-fold in films printed from amorphous aggregates compared to those from semicrystalline aggregates. This work shows that by tuning the precise structure of solution aggregates, the assembly pathways and the resulting thin-film morphology and device properties can be drastically tuned.

Nanomaterials with Supramolecular Assembly Based on AIE Luminogens for Theranostic Applications

One of the major pursuits of biomedical science is to develop advanced strategies for theranostics, which is expected to be an effective approach for achieving the transition from conventional medicine to precision medicine. Supramolecular assembly can serve as a powerful tool in the development of nanotheranostics with accurate imaging of tumors and real-time monitoring of the therapeutic process upon the incorporation of aggregation-induced emission (AIE) ability. AIE luminogens (AIEgens) will not only enable fluorescence imaging but will also aid in improving the efficacy of therapies. Furthermore, the fluorescent signals and therapeutic performance of these nanomaterials can be manipulated precisely owing to the reversible and stimuli-responsive characteristics of the supramolecular systems. Inspired by rapid advances in this field, recent research conducted on nanotheranostics with the AIE effect based on supramolecular assembly is summarized. Here, three representative strategies for supramolecular nanomaterials are presented as follows: a) supramolecular self-assembly of AIEgens, b) the loading of AIEgens within nanocarriers with supramolecular assembly, and c) supramolecular macrocycle-guided assembly via host-guest interactions. Meanwhile, the diverse applications of such nanomaterials in diagnostics and therapeutics have also been discussed in detail. Finally, the challenges of this field are listed in this review.