Multi-Stimuli-Responsive Polymer/Inorganic Janus Composite Nanoparticles

Multi-stimuli-responsive Janus composite nanoparticles (JNPs) of poly(N-isopropylacrylamide)-Fe₃O₄-poly(2-(dimethylamino)ethyl methacrylate)) (PNIPAM-Fe₃O₄-PDMEAMA) are synthesized by sequential reversible addition-fragmentation chain-transfer grafting of the polymer PNIPAM and atom-transfer radical polymerization grafting of the polymer PDMEAMA from the corresponding sides of modified Fe₃O₄ nanoparticles of ∼10 nm size. The hydrophilic/amphiphilic/hydrophobic reversible transition of the JNP can be triggered by pH and temperature since the wettability of the two polymers on the opposite sides is tunable accordingly. At a high pH value and a low surrounding temperature, applying near-infrared irradiation will induce the amphiphilic/hydrophobic transition owing to the photothermal effect of Fe₃O₄ NPs. The JNP can serve as a responsive solid emulsifier, and the stability and microstructure of the emulsions can be easily controlled by external stimuli such as the pH, temperature, and magnetic field.

Fabrication of self-healing nanocomposite hydrogels with the cellulose nanocrystals-based Janus hybrid nanomaterials

Janus nanomaterials possess remarkable prospects in the design of a series of smart materials with unique asymmetric properties. In this work, surface functionalized Janus cellulose nanocrystalline-type (CNCs-type) nanomaterials were manufactured by Pickering emulsion template and the construction of self-healing nanocomposite hydrogels has been realized. During emulsification, the mussel-inspired chemistry was employed to develop Janus nanocomposites. The extension of molecular chain of poly-lysine (PLL) and the polydopamine (PDA) coating were grafted on different sides of CNCs. Afterwards, the prepared nanocomposites were added to poly (acrylic acid) (PAA)-based hydrogels which formed by in-situ polymerization. The collaborative effect of metal-ligand coordination between the molecular chain of PLL, PDA coating, PAA chains and metal ions endowed the nanocomposite hydrogels with excellent mechanical properties (8.8 MPa) and self-healing efficiency (88.9%). Therefore, the synthesized Janus CNCs-PDA/PLL nanocomposites are expected to have diverse application in the development of smart materials with self-healing ability.

Janus Nanoparticles: From Fabrication to (Bio)Applications

Janus nanoparticles (JNPs) refer to the integration of two or more chemically discrepant composites into one structure system. Studies into JNPs have been of significant interest due to their interesting characteristics stemming from their asymmetric structures, which can integrate different functional properties and perform more synergetic functions simultaneously. Herein, we present recent progress of Janus particles, comprehensively detailing fabrication strategies and applications. First, the classification of JNPs is divided into three blocks, consisting of polymeric composites, inorganic composites, and hybrid polymeric/inorganic JNPs composites. Then, the fabrication strategies are alternately summarized, examining self-assembly strategy, phase separation strategy, seed-mediated polymerization, microfluidic preparation strategy, nucleation growth methods, and masking methods. Finally, various intriguing applications of JNPs are presented, including solid surfactants agents, micro/nanomotors, and biomedical applications such as biosensing, controlled drug delivery, bioimaging, cancer therapy, and combined theranostics. Furthermore, challenges and future works in this field are provided.

Design, Synthesis, and Self-Assembly of Janus Bottlebrush Polymers

Janus bottlebrush polymers are a class of special molecular brushes, which have two immiscible side chains on the repeating unit of the backbone. The characteristic architectures of Janus bottlebrush polymers enable unique self-assembly properties and broad applications. Recently, remarkable advances of Janus bottlebrush polymers have been achieved for polymer chemistry and material science. This review summarizes the synthetic strategies of Janus bottlebrush polymers, and highlights the self-assembly applications. Finally, the challenges and opportunities are proposed for the further development.