Photocontrollable volume phase transition of an azobenzene functionalized microgel and its supramolecular complex

A novel photo-responsive microgel (Azo-MG) was successfully prepared by grafting azobenzene moieties onto a poly(N-isopropylacrylamide-co-acrylic acid) microgel. Azo-MG can form a supramolecular complex with a-cyclodextrin (alpha-CD) through the host-guest interactions between azobenzene pendant groups and alpha-CD. Both Azo-MG and its supramolecular complex exhibit photocontrollable shifting of the volume phase transition temperature (VPTT). After UV irradiation, Azo-MG exhibited an increased VPTT, however, the supramolecular complex (Azo-MG with alpha-CD) exhibited a decreased VPTT. Near VPTT, the size of Azo-MG and its supramolecular complex can be regulated reversibly with UV and visible light. The as-prepared microgel has great potential as a building block in the designing of photo-responsive materials

Polymeric Micelles with Mesoporous Cores

Mesoporous polymer nanoparticles containing pores with sizes ranging from 2 to 50 nm are attractive for wide applications, such as catalysis, drug delivery, and separations. On the basis of nanometer-sized phase separation and cleavage reaction in the micellar cores, polymeric micelles with mesoporous cores are prepared in this research. A triblock terpolymer, consisting of one hydrophilic block and two mutually incompatible hydrophobic blocks covalently connected by a redox-responsive disulfide linkage, self-assembles into multicompartment micelles, a type of micelle with subdivided hydrophobic cores, in aqueous solution. Due to the incompatibility, the two hydrophobic blocks have nanometer-sized phase separation in the micellar cores, one in the discontinuous phase and the other in the continuous phase. Upon cleavage of the disulfide linkage, the discontinuous phase is dissolved in a selective solvent, and micelles with mesoporous cores are obtained. The average pore size is around 3 nm. Functionalization of the mesopores with functional compounds and inorganic nanoparticles renders these micelles suited for wide applications

Multiple-Responsive and Amphibious Hydrogel Actuator Based on Asymmetric UCST-Type Volume Phase Transition

Multiple-Responsive and Amphibious Hydrogel Actuator Based on Asymmetric UCST-Type Volume Phase Transitio

Water-Resistant Thermoelectric Ionogel Enables Underwater Heat Harvesting

The energy crisis is one of the most critical and urgent problems in modern society; thus, harvesting energy from ubiquitous low-grade heat energy with thermoelectric (TE) materials has become an available strategy in sustainable development. Recently, emerging ionic TE materials have been widely used to harvest low-grade heat energy, owing to their excellent performance in high ionic Seebeck coefficient, low thermal conductivity, and mechanical flexibility. However, the instability of ionic conductive materials in the underwater environment seriously suppresses underwater energy-harvesting, resulting in a waste of underwater low-grade heat energy. Herein, we developed a water-resistant TE ionogel (TEIG) with excellent long-term underwater stability utilizing a hydrophobic structure. Due to the hydrophobic polymer network and hydrophobic ionic liquid (IL), the TEIG exhibits high hydrophobicity and antiswelling capacity, which meets the requirement of environment stability for underwater thermoelectric application. Furthermore, the water resistance endows the TEIG with great thermoelectric performances in the underwater environment, including satisfactory ionic Seebeck coefficient, outstanding durability, and superior salt tolerance. Therefore, this investigation provides a promising strategy to design water-resistant TE materials, enabling a remarkable potential in harvesting low-grade heat energy under water

Chirality-Regulated Clusteroluminescence in Polypeptides

The low emission efficiency of clusteroluminogens restricts their practical applications in the fields of sensors and biological imaging. In this work, the clusteroluminescence of ordered/disordered polypeptides was observed, and the photoluminescence (PL) intensity of polypeptides can be modulated by the chirality of amino acid residues. Polyglutamates with different chiral compositions were synthesized, and the racemic polypeptides exhibited a significantly higher PL intensity than the enantiopure ones. This emission originates from the n–π* transition between CO groups of polypeptides and is enhanced by clusterization of polypeptides. CD and Fourier transform infrared spectra demonstrated that the enantiopure and racemic polypeptides form α-helix and random coil structures, respectively. The disordered polypeptides can form more chain entanglements and interchain interactions because of their high flexibility, leading to more clusterizations and stronger PL intensity. The rigidity of ordered helical structures restrains the chain entanglements, and the formation of intrachain hydrogen bonds between amide groups of the backbone impairs the interchain interaction between polypeptides, resulting in lower PL intensity. The PL intensity of the polypeptides can also be manipulated by the addition of urea or trifluoroacetic acid. Our study not only elucidates the chirality/order-based structure–property relationship of clusteroluminescence in peptide-based polymers but also offers implications for the rational design of fluorescent peptides/proteins

Synthetic Polypeptide Bioadhesive Based on Cation−π Interaction and Secondary Structure

Bioadhesives have garnered widespread attention in the biomedical field, for wound healing and tissue sealing. However, challenges exist due to the inferior performance of bioadhesives, including weak adhesion, poor biocompatibility, or lack of biodegradability. In this work, we demonstrate the fabrication of hydrogel adhesive based on polypeptides composed of lysine and glutamic acid. The cation−π interaction between the ammonium cations and phenyl groups endows the hydrogel with strong cohesion, and the hydrophobicity of the phenyl group significantly enhances the interaction between polypeptides and the substrate interface, leading to excellent adhesive performance. The equivalent molar ratio of ammonium cations and the phenyl group is beneficial for the enhancement of adhesiveness. Furthermore, we discover that the polypeptides with an α-helix exhibit better adhesiveness than the polypeptides with a β-sheet because the α-helical structure can increase the exposure of the side group on the polypeptide surface, which further strengthens the interaction between polypeptides and the substrate. Besides, this synthetic polypeptide adhesive can seal the tissue quickly and remain intact in water. This adhesive holds significant promise for application in wound healing and tissue sealing, and this study provides insight into the development of more peptide-based adhesives

Synthetic Polypeptide Bioadhesive Based on Cation−π Interaction and Secondary Structure

Bioadhesives have garnered widespread attention in the biomedical field, for wound healing and tissue sealing. However, challenges exist due to the inferior performance of bioadhesives, including weak adhesion, poor biocompatibility, or lack of biodegradability. In this work, we demonstrate the fabrication of hydrogel adhesive based on polypeptides composed of lysine and glutamic acid. The cation−π interaction between the ammonium cations and phenyl groups endows the hydrogel with strong cohesion, and the hydrophobicity of the phenyl group significantly enhances the interaction between polypeptides and the substrate interface, leading to excellent adhesive performance. The equivalent molar ratio of ammonium cations and the phenyl group is beneficial for the enhancement of adhesiveness. Furthermore, we discover that the polypeptides with an α-helix exhibit better adhesiveness than the polypeptides with a β-sheet because the α-helical structure can increase the exposure of the side group on the polypeptide surface, which further strengthens the interaction between polypeptides and the substrate. Besides, this synthetic polypeptide adhesive can seal the tissue quickly and remain intact in water. This adhesive holds significant promise for application in wound healing and tissue sealing, and this study provides insight into the development of more peptide-based adhesives

Investigation on the Structure of Water/AOT/IPM/Alcohols Reverse Micelles by Conductivity, Dynamic Light Scattering, and Small Angle X-ray Scattering

We have systematically investigated the effect of alcohols (ethanol, propanol, butanol, and pentanol) on the structure of the water/AOT/IPM system using conductivity, dynamic light scattering (DLS), and small-angle X-ray scattering (SAXS) techniques. The results show that no percolation phenomenon is observed in the water/AOT/IPM system, whereas the addition of ethanol (propanol and butanol) induces apparently percolation. The threshold water content (<i>W</i>_p) depends closely on the alcohol type and concentration. The effect of alcohols on the conductance behavior is discussed from the physical properties of alcohols, the interfacial flexibility, and the attractive interactions between droplets. The hydrodynamic diameter of droplets (<i>d</i>_H) obtained from DLS increases markedly with the increase in water content (<i>W</i>₀); however, it decreases gradually with increasing alcohol chain length and concentration. SAXS measurements display distinctly the shoulder, the low hump peaks, and the heavy tail phenomenon in the pair distance distribution function <i>p</i>(<i>r</i>) profile, which rely strongly on the alcohol species and its concentration. The gyration radius (<i>R</i>_g) increases with increasing <i>W</i>₀, and decreases with the increase of alcohol chain length and concentration. Schematic diagram of the conductance mechanism of water/AOT/IPM/alcohol systems is primarily depicted. Three different phases of the discrete droplets, the oligomers, and the isolated ellipsoidal droplets existed in the different <i>W</i>₀ ranges correspond to three different stages in the conductivity–<i>W</i>₀ curve. Coupling the structure characteristics of reverse micelles obtained from DLS and SAXS techniques with conductivity could be greatly helpful to deeply understand the percolation mechanism of water/AOT/IPM/alcohols systems