Janus Composite Nanorod from a Molecular Bottlebrush Containing a Block Copolymer

The asymmetric ABC-type Janus polymer composite nanorods are synthesized by the in situ preferential growth of functional materials against the molecular bottlebrush containing a triblock copolymer of poly­(ethylene oxide)-<i>b</i>-poly­(2-meth­acryl­oyl­oxy­ethyl pentyn­oate-<i>g</i>-poly­(acrylic acid))-<i>b</i>-polystyrene. PEO and PS single chains are terminated onto the opposite ends of the composite nanorods. The two polymer chains are responsible for amphiphilic performance, while the composite nanorod is responsible for the functionality. The Janus nanorods can stand vertically at an emulsion interface, making the interfaces easily functionalized and manipulated. Protection of the PAA molecular bottlebrush via electrostatic interaction is important to obtaining individual nanorods at high solid contents. A huge family of Janus composite nanorods is expected by changing the compositions of the two polymer chains and the nanorod

Polymeric Janus Nanosheets by Template RAFT Polymerization

We report a general method to synthesize polymeric Janus nanosheets (PJS) by sequential RAFT grafting from a template particle surface. Layer number and composition of the PJS are tunable by feeding sequence and type of monomers. The <i>c</i>PNIPAM–PS PJS is flexible and thermal responsive, which can form a scrolled superstructure. A dually responsive <i>c</i>PAA–PNIPAM PJS is derived by hydrolysis of <i>c</i>P<i>t</i>BA–PNIPAM. Accordingly, stability of the emulsion with the <i>c</i>PAA–PNIPAM PJS is triggered by alternation of pH or/and temperature

Polymer-Fe₃O₄ Composite Janus Nanoparticles

A Fe₃O₄ nanoparticle (NP) based on composite Janus NP with single polymer chain is prepared by termination of the modified Fe₃O₄ NP with the anionic living polymer chain. The requisite that the polymer chain should be sufficiently large over the NP diameter determines the grafting of single polymer chain. From the opposite side of the NP surface, functional species can be selectively grown for example grafting responsive PNIPAM by ATRP. Besides simple combination of the thermal and magnetic responsive performances of different components, the PS–Fe₃O₄–PNIPAM composite Janus NP shows additional interactive performance such as NIR-triggered Janus/hydrophobic transition at low surrounding temperature below LCST ∼ 32 °C

Conelike Janus Composite Particles

Conelike cross-linked PS particles are polymerized at a patchy emulsion interface. The PS particles synthesized in the dispersed paraffin phase immigrate toward the interface due to the Pickering effect. At the triple phase contact line, the particles are squeezed into cone shape under an outward convex interfacial tension mismatch. The conelike PS particles are adhered to paraffin sphere surface and synchronously protected, which allows selective modifications of the two sides. The Janus particles can self-organize into superstructures in dispersions. Robust coatings are easily fabricated from the Janus particles, whose wettability is tunable from highly adhesive for water to superhydrophobic by simply changing the size distribution of the Janus particles

Coral-like Janus Porous Spheres

A Janus porous sphere with a coral-like microstructure is prepared by stepwise dealloying a metallic alloy sphere and sequential modification (for example, using silanes and polymers). Nanoscale coral-like microstructure of the internal skeleton gives remarkable capillary force, thus accelerating the mass transportation. Starting from the outer layer of the sphere, stepwise dealloying can achieve different layers inwardly, thus introducing different composition and performance. As an example, poly­(ethylene glycol)–poly­(<i>N</i>-isopropylacrylamide) (PEG–PNIPAM)- and poly­(ethylene glycol)–poly­(<i>N</i>,<i>N</i>-diethylamino-2-ethylmethacrylate) (PEG–PDEAEMA)-responsive Janus porous spheres can quickly capture oil by simply changing temperature or pH. Similarly, release is also triggered

Light-Triggered Responsive Janus Composite Nanosheets

We report the synthesis of light-triggered Janus composite nanosheets and their Janus performance. Onto the amine-group terminated side of silica Janus nanosheets, a photo-responsive spiropyran-containing polymer (PSPMA) brush has been prepared by ATRP, while the other side terminated with hydrophobic octyl groups is preserved. Upon UV irradiation, the hydrophobic PSPMA side becomes hydrophilic since the hydrophobic spiropyran changes to the hydrophilic zwitterionic merocyanine form (or vice versa with visible light). Consequently, the PSPMA/silica composite nanosheets become Janus from hydrophobic or vice versa. The Janus composite nanosheets can serve as a responsive solid emulsifier, thus the stability of the emulsions can be remotely triggered with light. Unlike those pH- or temperature-responsive Janus materials, the light-triggering process requires no additional input of chemicals or thermal energy

Reversible Transformation of Nanostructured Polymer Particles

A reversible transformation of overall shape and internal structure as well as surface composition of nanostructured block copolymer particles is demonstrated by solvent-adsorption annealing. Polystyrene-<i>b</i>-poly­(4-vinylpyridine) (PS-<i>b</i>-P4VP) pupa-like particles with PS and P4VP lamellar domains alternatively stacked can be obtained by self-assembly of the block copolymer under 3D soft confinement. Chloroform, a good solvent for both blocks, is selected to swell and anneal the pupa-like particles suspended in aqueous media. Reversible transformation between pupa-like and onion-like structures of the particles can be readily tuned by simply adjusting the particle/aqueous solution interfacial property. Interestingly, poly­(vinyl alcohol) (PVA) concentration in the aqueous media plays a critical role in determining the particle morphology. High level of PVA concentration is favorable for pupa-like morphology, while extremely low concentration of PVA is favorable for the formation of onion-like particles. Moreover, the stimuli-response behavior of the particles can be highly suppressed through selective growth of Au nanoparticles within the P4VP domains. This strategy provides a new concept for the reversible transformation of nanostructured polymer particles, which will find potential applications in the field of sensing, detection, optical devices, drug delivery, and smart materials fabrication

Robust Reactive Janus Composite Particles of Snowman Shape

We present a facile approach toward snowman-like silica@PDVB/PS Janus particles by seed emulsion polymerization using a gelable monomer MPS against a PDVB/PS hollow particle. Individual silica bulge is protruded from the seed particle surface, whose size is tunable. The silica@PDVB Janus particles are derived after dissolution of PS, which are robust to tolerate against organic solvents. Both sides are reactive for selective modifications to grow desired materials with tunable wettability and functionality. As solid emulsifiers, the Janus balance of the particles is tunable from more hydrophobic to more hydrophilic by changing either aspect size ratio or composition of the two sides

Light-Responsive Janus-Particle-Based Coatings for Cell Capture and Release

A robust light-responsive coating based on Janus composite particles is achieved. First, strawberry-like silica Janus particles are synthesized by the sol–gel process at a patchy emulsion interface. One side of the silica Janus particles possesses nanoscale roughness, and the other side is flat. Then, spiropyran-containing polymer brushes are grafted onto the coarse hemispherical side of the as-synthesized Janus particles, and the other flat side is modified with imidazoline groups. The light-responsive polymer brush-terminated coarse hemispherical sides direct toward the air when the Janus composite particles self-organize into a layer on the surface of epoxy resin substrate. The imidazoline groups react with the epoxy groups in the epoxy resin to form a robust smart coating. The coating can be reversibly triggered between hydrophobic and hydrophilic by UV and visible-light irradiation, which is attributed to the isomerization of spiropyran moieties. When the hydrophobic ring-closed spiropyran form is prominent, HeLa cells can be effectively captured onto the coating. After UV light irradiation, the ring-closed spiropyran form changes to the hydrophilic ring-opened zwitterionic merocyanine form, and then the captured cells are released. This work shows promising potential for engineering advanced smart biointerfaces

Janus Nanocage toward Platelet Delivery

The platelet-shaped Janus nanocages with a mesoporous silica shell are prepared. PEG moiety onto the exterior surface is responsible for good dispersity in water. The graphene sheet inside the cavity is responsible for hydrophobic performance to selectively capture hydrophobic species, and photothermal effect by NIR irradiation. As a biocompatible DOX-loaded Janus platelet delivery, HeLa cell cytotoxicity is greatly enhanced under NIR irradiation. There exists a synergetic effect between the chemotherapy and photothermal therapy