Polymeric Janus Nanosheets by Template RAFT Polymerization

Preparation of Janus Polymer Nanosheets and Corresponding Oil Displacement Properties at Ultralow Concentration

Conventional methods for preparing Janus nanosheets, including graphene oxide-based nanosheets, molybdenum disulfide-based nanosheets, and silicon dioxide-based nanosheets, as well as polymer-based nanosheets, involve complicated procedures, poor repeatability, and difficulty in imparting Janus properties, which hinder further application. Here, the present authors develop a facile modified suspension polymerization method for preparing Janus polymer nanosheets, in which deep eutectic solvents completely replace water as the continuous phase. Janus polymer nanosheets can be fabricated using common hydrophobic and hydrophilic monomers, such as styrene (St), butyl acrylate (BA), acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acryloyloxyethyl trimethylammonium chloride (DAC), and maleic anhydride (MAH). Additionally, the thickness of the Janus polymer nanosheets can be precisely controlled in a range from 40 to 100 nm by adjusting the volume ratio of higher alkanes to the hydrophobic monomer. Subsequently, the emulsification properties of polystyrene-based nanosheets were evaluated, showing better performance at concentrations ranging from 1 to 50 mg/L compared with higher concentrations. This observation aligns with the corresponding reduction in interfacial tension and changes in the moduli of the interfacial film. Moreover, the adsorption of the nanosheets onto the core alters its wettability, changing it from a water-wettable state to an oil-wettable state. Consequently, a series of core flooding tests reveal that the poly(St-co-AM), poly(St-co-MAH), and poly(St-co-AMPS) nanosheets enhance oil recovery and reduce injection pressure at ultralow concentrations (50 mg/L).

Construction of polymer brush-decorated amphiphilic Janus graphene oxide nanosheets via a Pickering emulsion template for catalytic applications

2D amphiphilic Janus GO nanocatalysts were prepared using Pickering emulsions and grafted polymer brushes, with excellent performance in homogeneous and interfacial catalysis.

Facile asymmetric modification of graphene nanosheets using κ-carrageenan as a green template

The synthesis of Janus nanosheets using κ-carrageenan (κ-Ca) as a green template endows a greener and more straightforward method compared to traditional approaches of using wax template. We hypothesize that the hydrogen bonding interaction between κ-Ca and graphene oxide (GO) allows partial masking of GO's single facet, paving the way for the asymmetric modification of the exposed surface. GO is first encapsulated within the porous hydrogel matrix formed by κ-Ca to isolate one of the facets. The exposed surface was then selectively hydrophobized to produce an amphiphilic asymmetrically modified graphene oxide (AMGO). The properties of AMGO synthesized under different κ-Ca/GO ratios were studied. The κ-Ca/GO interactions and the properties of GO and AMGO were investigated and characterized. AMGO was successfully produced with a yield of 90.37 % under optimized synthesis conditions. The separation of κ-Ca and AMGO was conducted without organic solvents, and the κ-Ca could be subsequently recovered. Furthermore, the porous hydrogel matrix formed by κ-Ca and GO exhibited excellent shape-retaining properties with high thermal tolerance of up to 50 °C. Given these benefits, this newly developed method endows sustainability and open the possibility of formulating more flexible material synthesis protocols.

Preparation and applications of freestanding Janus nanosheets

In the family of Janus nanomaterials, Janus nanosheets possess not only the advantages of Janus nanomaterials, but also the advantages of two-dimensional nanosheets, endowing them with many extraordinary properties. Therefore, Janus nanosheets have great potential in the fields of interfacial engineering, catalysis, and molecular recognition. This review summarizes and discusses the recent advances in both the preparation and applications of freestanding Janus nanosheets. After a short introduction to different types of Janus nanosheets, a variety of methods for preparing freestanding Janus nanosheets are introduced, including the surface reaction, interface reaction, emulsion reaction, self-assembly, and stripping of non-Janus nanosheets, as well as selective grafting of existing Janus nanosheets. Then, the wide applications of Janus nanosheets in the fields of emulsification, catalysis, polymer reinforcement, nanomotors, and molecular recognition are summarized in detail. Finally, a discussion on the remaining challenges and future perspectives in this field is included. This review will not only deepen the understanding of Janus nanosheets, but also benefit the designs and fabrications of extraordinary and multi-functional Janus nanosheets.

The design and biomedical applications of self-assembled two-dimensional organic biomaterials

Self-assembling 2D organic biomaterials exhibit versatile abilities for structural and functional tailoring, as well as high potential for biomedical applications.