We report the first example of the fabrication of pure, single-chain Janus particles (SCJPs). The SCJPs were prepared by double-cross-linking an A-b-B diblock copolymer in a common solvent. Inevitably, the double-cross-linking led to a mixture containing not only SCJPs but also multichain particles and irregular single-chain particles. Under well-controlled conditions, the SCJPs in the mixture self-assemble with high exclusivity to form regularly structured macroscopic assemblies (MAs) with a crystal-like appearance that precipitate from the suspension. Pure SCJPs that are uniform in size, shape and Janus structure were efficiently prepared by collection and dissociation of the MAs. Block copolymers with different structural parameters were successfully used for the exclusive self-assembly (ESA), and pure SCJPs with varied structural parameters were produced, confirming the reliability of the ESA method.

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Ultrasound-controlled drug release is a very promising technique for controlled drug delivery due to the unique advantages of ultrasound as the stimulus.

Energetic Metal Organic Frameworks (EMOFs) have been a hotspot of research on solid propellants in recent years. In this paper, research on the application of EMOFs-based burning rate catalysts in solid propellants was reviewed and the development trend of these catalysts was explored. The catalysts analyzed included monometallic organic frameworks-based energetic burning rate catalysts, bimetallic multifunctional energetic burning rate catalysts, carbon-supported EMOFs burning rate catalysts, and catalysts that can be used in conjunction with EMOFs. The review suggest that monometallic organic frameworks-based burning rate catalysts have relatively simple catalytic effects, and adding metal salts can improve their catalytic effect. Bimetallic multifunctional energetic burning rate catalysts have excellent catalytic performance and the potential for broad application. The investigation of carbon-supported EMOFs burning rate catalysts is still at a preliminary stage, but their preparation and application have become a research focus in the burning rate catalyst field. The application of catalysts that can be compounded with EMOFs should be promoted. Finally, environmental protection, high energy and low sensitivity, nanometerization, multifunctional compounding and solvent-free are proposed as key directions of future research. This study aims to provide a reference for the application of energetic organic burning rate catalysts in solid propellants.

Nitrile N-oxide-based click ligation is a very promising technique for polymer crosslinking due to the unique advantages of catalyst-free and byproduct-free reactions. For this technique, nitrile N-oxides that are sufficiently stable at room temperature and have high reactivity under mild conditions are very desirable. Usually, neighboring bulky substituents are introduced to enhance the stability of nitrile N-oxides, which however bring the reactivity down due to the high steric hindrance. Herein, methyl groups, small-sized substituents, were introduced into the o,o′-positions of phenyl nitrile N-oxides to enable high stability and high reactivity. Thus, several novel aromatic nitrile N-oxides were synthesized. Among them, ditopic aromatic nitrile N-oxides were prepared through three simple steps including etherification, oximation, and oxidative dehydrogenation, whereas stable tritopic aromatic nitrile N-oxides were synthesized by directly introducing the nitrile N-oxide functionality into the corresponding trifunctional compounds to avoid undesirable side reactions. These nitrile N-oxides as ligation reagents exhibited very high reactivity, and efficient catalyst-free crosslinking of natural rubber was achieved at room temperature to give elastomers with good mechanical properties, revealing the potential of such nitrile N-oxides as useful crosslinkers for unsaturated bondcontaining polymers. This work provides reliable synthesis of stable ditopic/tritopic aromatic nitrile N-oxides, broadening the application of the nitrile N-oxide-based click ligation technique toward catalyst-free and byproduct-free polymer crosslinking.