Flexible polymer at the interface of a liquid / liquid nanoparticles Janus

A fully liquid system can be constructed by the addition of nanoparticles (NPs) at the interface between two immiscible liquids, provides a variety of possibilities to develop in response to binding of the active material by sealing or the like. If the two liquids interact with the colloidal particles can be smaller than the interaction energy between the two liquids, the colloidal particles tend to aggregate at the interface of two immiscible liquids to reduce the interfacial tension and free energy. Thus, the emulsion may be produced by polystyrene latex particles of an oil-in-water (o / w) or water-oil (w / o) packet assembler micron size at the interface. Wherein, Janus nanoparticles (JNPs) are on opposite sides of the core NPs functionalized with hydrophilic and hydrophobic ligands NPs, and lower the interfacial tension will gather at the water / oil interface. Previous studies showed that, JNPs domains can stabilize the polymer blend, or may be regulated by changing the shape of the kinetics JNPs of JNPs. The flexible nature of the special JNPs interface allows various modifications: respond to external stimulus, the configuration of the polymer chains at the interface can control assembly mechanical properties. By changing the strength of the interaction between the liquid and the corona chains, may be varied to maintain the flexible JNPs binding energy at the interface, the control response can be further flexible JNPs assembly. 液/液界面处的柔性聚合物Janus纳米颗粒

[introduction] achievement

Based on this, the University of Massachusetts Thomas P. Russell (Corresponding author) team reported a polystyrene -b- poly (butadiene) -b- poly (methyl methacrylate) (PS-PBPMMA) triblock terpolymer made from flexible polymer Janus nanoparticles (JNPs) . Then, we focused on the molecular structure of the flexible JNPs in a water / oil interface at – the assembly and regulation interface interfacial activity. Since the flexible JNPs crosslinked by about PB PS and PMMA coronae core composition, the researchers nanoparticles expressed as SBM. As shown in FIG. 1, three different researchers JNPs prepared, wherein the weight fraction of the polybutadiene core 10-20-30%, and the total molecular weight and Janus balance remains constant. Since the crosslinked core is harder than the PB and PS PMMA coronae, so JNPs with increasing softness PB core size decreases. That is, the longer the polymer chains with respect to PB core, the softer JNPs, resulting in an initial assembly JNPs lateral bulk density is lower. As shown in FIG. 1, a light is flashed to characterize different PB core size by TEM and dynamic JNPs a particle size of 22 nm (SBM-10), 27 nm (SBM-20), 55 nm (SBM-30). Further, JNPs of surfactant may also be incorporated to further adjust the lithium ion complexed by the aqueous phase and PMMA chains. In summary, this work provides a basic understanding of the flexible JNPs water / oil accumulation at the interface, and to provide a flexible adjustment JNPs in the liquid / liquid interface at the surface density of the strategy to be designed smart responsive structured liquid system. The research results entitled \”Soft Polymer Janus Nanoparticles at Liquid / Liquid Interfaces\” published in internationally renowned journals Angew. Chem. Int. Ed. on.

液/液界面处的柔性聚合物Janus纳米颗粒
FIG. 1, a TEM different core size JNPs FIG nuclear particle size

[Explanation graphic]

Neat 15 SBM JNPs μL droplet was immersed in toluene, and measuring the interfacial tension between two liquids (IFT). Since the assembly SBM JNPs at the interface, IFT initial drop. IFT found to maintain a balance with the increase of SBM JNPs concentration decreases. For low concentration JNPs (0.08 mg / mL), IFT show an initial rapid drop followed by a period of IFT falls more slowly. As absorb more JNPs has been JNPs at the interface must be subjected to further conformational change to create more space. With increasing concentration JNPs, JNPs initially adsorbed to the interface speed is too fast to measure and observe the gradual reduction of the representative JNPs rearrangement and reconfiguration in a long time. In addition, the researchers also summed up the concentration-dependent balance of the IFT. SBM30 NP has a maximum and a hard core and the shortest chain corona similar, is greatly reduced because the degree of freedom of corona chain, and therefore non-Often quickly achieve balance IFT. With the improvement JNPs coverage, more chains will be adsorbed to the interface, so that the PMMA has been adsorbed JNPs chain slack.

液/液界面处的柔性聚合物Janus纳米颗粒
FIG 2, SBM evolution and equilibrium interfacial tension

In addition, researchers investigated having a crosslinked PB core at a time different concentrations JNPs toluene solution with water interfacial tension and only NPs having homogeneous PMMA corona (non JNPs) a. PMMA corona molecular chain is 90 k, the weight fraction of the core is 20% PB. Nuclear size and SBM20 similar. Depending tonometry using the formula indicated that these non JNPs SBM20 as effective with reduced water / toluene interfacial tension. Because the interfacial tension of the water much / PMMA is / toluene lower than water, so the chain PMMA segregated at the interface, to minimize the water / toluene contacts. However, in the process of reducing the volume required is much reduced (35%), so that the non JNPs assembly wrinkling. This is due to the reconfiguration of the non-JNPs caused JNPs contrast, placed at the interface of the non-JNPs more chain PMMA (per particle). Thus, a greater number of NPs each strand extending at the interface, resulting in fewer wrinkles compression.

液/液界面处的柔性聚合物Janus纳米颗粒
FIG. 3, the droplets immersed in a toluene solution, water and non JNPs JNPs and interfacial tension of different JNPs
液/液界面处的柔性聚合物Janus纳米颗粒
FIG 4 , JNPs assembled in a case where volume reduction and subsequent relaxation schematic

[summary]

in conclusion, the researchers proved that the liquid can be flexible JNPs / liquid interface is assembled, even if one of the two liquids insoluble corona chain. See corona chain diffusion at the interface to reduce the elastic restoring force equilibrium interfacial tension. corona shorter chain, which may be extended, the less so the more dense coverage. After compression, the flexible JNPs may be reconfigured, thereby reducing the applied pressure. In the case of PMMA to water, salt ions complexed with PMMA can promote dissolution in the aqueous phase. As the complexity, flexibility JNPs area density at the interface with a corresponding change in the compression of the assembly in response to increases. In summary, this work provides a control to adjust the density and the interfacial characteristics JNPs interface convenient method. References:

Soft Polymer Janus Nanoparticles at Liquid / Liquid Interfaces (Angew Chem Int Ed, 2020, DOI:…. 10.1002 / anie.202004162)

Link:

https: // onlinelibrary. wiley.com/doi/abs/10.1002/anie.202004162

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