Scientific publications

A fully coupled model for mass and heat transport, mechanics, and chemical reactions with trapping is proposed. It is rooted in non-equilibrium rational thermodynamics and assumes that displacements and strains are small. Balance laws for mass, linear and angular momentum, energy, and entropy are stated. Thermodynamic restrictions are identified, based on an additive strain decomposition and on the definition of the Helmholtz free energy. Constitutive theory and chemical kinetics are studied in order to finally write the governing equations for the multi-physics problem. The field equations are solved numerically with the finite element method, stemming from a three-fields variational formulation. Three case-studies on vacancies redistribution in metals, hydrogen embrittlement, and the charge–discharge of active particles in Li-ion batteries demonstrate the features and the potential of the proposed model.

Supramolecular chemistry has provided versatile and affordable solutions for the design of intelligent soft materials, but it cannot be applied in stiff materials. This paper describes a new concept for the design of high-performance supramolecular thermosets by using the noncovalent cation–π interaction as cross-linking. These supramolecular thermosets are a class of infusible and insoluble stiff polymers having excellent mechanical properties even at temperatures exceeding 300 °C. The cation–π interaction can be locally and reversibly installed and removed by aqueous treatments at high or low pH, respectively. Local manipulation of cross-linking confers these thermosets with multiple stimuli-responsive functions, such as recyclability, healability, adhesion, and nondestructive detection of cross-linking and mechanical properties.

Abstract Traditional dynamic adaptive materials rely on an atomic/molecular mechanism of phase transition to induce macroscopic switch of properties, but only a small number of these materials and a limited responsive repertoire are available. Here, liquid as the adaptive component is utilized to realize responsive functions. Paired with a porous matrix that can be put in motion by an actuated dielectric elastomer film, the uncontrolled global flow of liquid is broken down to well-defined reconfigurable localized flow within the pores and conforms to the network deformation. A detailed theoretical and experimental study of such a dynamically actuated liquid-infused poroelastic film is discussed. This system demonstrates its ability to generate tunable surface wettability that can precisely control droplet dynamics from complete pinning, to fast sliding, and even more complex motions such as droplet oscillation, jetting, and mixing. This system also allows for repeated and seamless switch among these different droplet manipulations. These are desired properties in many applications such as reflective display, lab-on-a-chip, optical device, dynamic measurements, energy harvesting, and others.

Abstract In this study a surfactant-free and shape controllable preparation of microgel beads using super-repellent surfaces is reported. The extreme hydrophobicity and the interfacial tension of the liquid force the droplet of a gel precursor solution into spherical shape on a superamphiphobic or hemisphere shape on slippery surface. During gelation on the surface, the shape is maintained. Living cells and molecules, which hardly interact with substrate, can be therefore encapsulated in situ. The encapsulation of MC3T3 mouse osteoblast is demonstrated as a proof of concept.

We demonstrate a hydrogel bowl capable of selectively and rapidly collecting spilled oil while floating on water. The bowl has macroscopic openings in its sidewall, and its surface is first coated with octadecyltrichlorosilane (OTS) and then with diffusion pump oil, which imparts exceptional hydrophobic, oleophilic, and high oil wettability properties. The use of a hydrogel makes it possible to obtain surface hydrophobicity and oleophilicity, while also being inexpensive, eco-friendly, and easy to fabricate. Using a prototype of the bowl and a small pump system, we demonstrate that oils with a broad range of viscosities (2.7–2000.0 cSt at 20–40 °C) are more rapidly and efficiently collected from the surface of both pure water and seawater than with any other reported technique. The hydrogel bowl can collect oil for more than one month without losing its efficiency and can be stored in oil for reuse. Therefore, such hydrogel bowls represent a new alternative to conventional oil spill remediation techniques.

The development of switchable white-light emitters is extremely challenging but urgently needed for various applications. We describe a class of switchable fluorescent polymeric nanoparticles (SFPNs) that can alternate their emission color among stable white, cyan, or pink. These SFPNs consist of a dye with cyan-light emission and a spiropyran (SP) derivative with photochromism. When the SP derivative is transferred to its merocyanine state, fluorescence resonance energy transfer (FRET) occurs from the cyan dye to the merocyanine one. In a rational design of transfer efficiency, a stable white-light emission is achieved. This white-light emission can be switched to the cyan-light one upon photoirradiation or pink-light one by solvent-induced swelling. Such multi-color fluorescent alternation is reversible and therefore allows for data encryption. Because of the facile synthesis, excellent long-term stability, fast photo-responsibility, high-contrast fluorescence, and outstanding switchability of these nanoparticles, we envision that they should have great potential in various applications such as high-resolution imaging, white luminescence, and data encryption.

Both phototriggered growth and removal of polymer chains from surfaces are efficient ways to finely tune interface properties. Combining these two capabilities in one system with independent control can significantly increase the feasibility of photoregulation on surface modification but has not been reported yet. Herein we describe a novel approach to control both the growth and the detachment of polymer brushes independently by light with different wavelengths. The approach is based on a nitrodopamine-based initiator (NO2–BDAM) which contains a catechol structure for surface modification, alkyl bromide group for radical polymerization, and o-nitrophenyl ethyl moiety for photolysis. When dimanganese decacarbonyl (Mn2(CO)10) was applied together with NO2–BDAM as an initiating system, visible light (460 nm) can be used to trigger the site-specific growth of polymer brushes. Resulting polymer brushes can be selectively removed by UV light (360 nm). This method is suitable for different monomers on various substrates, suggesting a facile and robust method to regulate surface properties.

Abstract Collection of two optically pure enantiomers in a single crystallization process can significantly increase the chiral separation efficiency but this is difficult to realize. Now a self-reporting strategy is presented for visualizing the crystallization process by a dyed self-assembled inhibitor made from the copolymers with tri(ethylene glycol)-grafting polymethylsiloxane as the main chain and poly(N6-methacryloyl-l-lysine) as side chains. When applied with seeds together for the fractional crystallization of conglomerates, the inhibitors can label the formation of the secondary crystals and guide the complete separation process of two enantiomers with colorless crystals as the first product and red crystals as the second. This method leads to high optical purity of d/l-Asn⋅H2O (99.9 % ee for d-crystals and 99.5 % for l-crystals) in a single crystallization process. It requires a small amount of additives and shows excellent recyclability.