L-Arginine based polyester amide/hyaluronic acid hybrid hydrogel with dual anti-inflammation and antioxidant functions for accelerated wound healing

Nowadays, there are still many challenges to skin regeneration. As a new type of skin substitute, hydrogel has emerging gradually with its excellent properties. However, it is still a challenge to combine with biological active agents to facilitate skin regeneration. Under the circumstance, we synthesized argininebased poly(ester amide)(Arg-PEA) and hyaluronic acid(HA-MA), and combined them into new hybrid hydrogels via photo-crosslinking. We found that the internal structure and physicochemical...     

Hydrogen-Bond Cyclization Programming of Ultrasensitive Esters and Its Application in Gene Delivery

The ester bond as a universal linker has recently been applied in gene delivery systems owing to its efficient gene release by electrostatic repulsion after its cleavage. However, the ester bond is nonlabile and is difficult to cleave in cells. This work reports a method in which a secondary amine was introduced to the β-position of the ester bond to generate a hydrogen-bond cyclization (HBC) structure that can make the ester bond hydrolysis ultrafast. A series of molecules comprising ultrasensitive esters that can be activated by H₂O₂ were synthesized, and it was found that those able to form an HBC structure showed complete ester hydrolysis within 5 h in both water and phosphate-buffered saline solution, which was several times faster than other methods reported. Then, a series of amphiphilic poly(amidoamine) dendrimers were constructed, comprising the ultrasensitive ester groups for gene delivery; it was found that they could effectively release genes under quite a low concentration of H₂O₂ (<200 μm ) and transport them into the nucleus within 2 h in Hela cells with high safety. Their gene transfection efficiencies were higher than that of PEI_25k. The results demonstrated that the hydrogen-bond-induced ultrasensitive esters could be powerfully applied to construct gene delivery systems.     

Imide-Functionalized Polymer Semiconductors

Imide-functionalized π-conjugated polymer semiconductors have received a great deal of interest owing to their unique physicochemical properties and optoelectronic characteristics, including excellent solubility, highly planar backbones, widely tunable band gaps and energy levels of frontier molecular orbitals, and good film morphology. The organic electronics community has witnessed rapid expansion of the materials library and remarkable improvement in device performance recently. This review summarizes the development of imide-functionalized polymer semiconductors as well as their device performance in organic thin-film transistors and polymer solar cells, mainly achieved in the past three years. The materials mainly cover naphthalene diimide, perylene diimide, and bithiophene imide, and other imide-based polymer semiconductors are also discussed. The perspective offers our insights for developing new imide-functionalized building blocks and polymer semiconductors with optimized optoelectronic properties. We hope that this review will generate more research interest in the community to realize further improved device performance by developing new imide-functionalized polymer semiconductors.     

Bis-tridentate IrIII Phosphors Bearing Two Fused Five-Six-Membered Metallacycles: A Strategy to Improved Photostability of Blue Emitters

Iridium complexes bearing chelating cyclometalates are popular choices as dopant emitters in the fabrication of organic light-emitting diodes (OLEDs). In this contribution, we report a series of blue-emitting, bis-tridentate Ir^III complexes bearing chelates with two fused five-six-membered metallacycles, which are in sharp contrast to the traditional designs of tridentate chelates that form the alternative, fused five-five metallacycles. Five Ir^III complexes, Px-21 – 23 , Cz-4 , and Cz-5 , have been synthesized that contain a coordinated dicarbene pincer chelate incorporating a methylene spacer and a dianionic chromophoric chelate possessing either a phenoxy or carbazolyl appendage to tune the coordination arrangement. All these tridentate chelates afford peripheral ligand–metal–ligand bite angles of 166–170°, which are larger than the typical bite angle of 153–155° observed for their five-five-coordinated tridentate counterparts, thereby leading to reduced geometrical distortion in the octahedral frameworks. Photophysical measurements and TD-DFT studies verified the inherent transition characteristics that give rise to high emission efficiency, and photodegradation experiments confirmed the improved stability in comparison with the benchmark fac-[Ir(ppy)₃] in degassed toluene at room temperature. Phosphorescent OLED devices were also fabricated, among which the carbazolyl-functionalized emitter Cz-5 exhibited the best performance among all the studied bis-tridentate phosphors, showing a maximum external quantum efficiency (EQE_max) of 18.7 % and CIE_x,y coordinates of (0.145, 0.218), with a slightly reduced EQE of 13.7 % at 100 cd m⁻² due to efficiency roll-off.     

Liquid crystalline behaviours of some 3-perfluoroalkylbenzoate esters

A series of 3-perfluoroalkylbenzoate esters are synthesised. They tend to exhibit enantiotropic SmA and SmC phases. The clearing points are decreased with increasing the alkoxy chain length and show odd-even effect. With increasing the fluorocarbon chain length, the melting and clearing points increase; however, the SmC phase is suppressed.     

Coordinate Bond Breaking Induced by Collapse of Poly(\begin{document}$N$\end{document}-isopropyl acrylamide) as Ligands of a Rare Earth Complex

A novel water-soluble luminescent complex consisting of Eu(ally-dbm)\begin{document}$_3$\end{document}-2Tppo and poly(N-isopropyl acrylamide) (PNIPAM) is synthesized through a series of chemical reactions. The structure of the complex is characterized by TGA, GPC, HNMR, and the thermal-responsive fluorescence of the complex in aqueous solution is investigated. It is found that PNIPAM collapse above the lower critical solution temperature causes the coordination bond breaking, leading to weakening of the fluorescence from Eu\begin{document}$^{3+}$\end{document} and enhancing of the fluorescence from the ligands. When temperature decreases, the fluorescence from Eu\begin{document}$^{3+}$\end{document} is found to boost up and the fluorescence from ligands weakens accordingly. It is deduced from this phenomenon that the ligands re-coordinate with europium ions again along with the temperature decreasing, which is further confirmed by IR measurements. This thermal-responsive fluorescence is of reversibility, which can be used as molecular probes for biological imaging and collapse studying of PNIPAM.     

Athermal and Soft Multi-Nanopatterning of Azopolymers: Phototunable Mechanical Properties

Imprinting nanopatterns on flexible substrates has diverse applications in advanced fabrication. However, the traditional thermal nanoimprint lithography (T-NIL) often causes shrinkage upon cooling. Here, a simple yet versatile method is introduced to fabricate multiple nanopatterns on a flexible substrate coated with an azopolymer by combining athermal nanoimprint lithography (AT-NIL) and photolithography. The azopolymer has various mechanical properties upon photoirradiation: 1) phototunable glass-transition temperatures (T_g) and concomitantly photoinduced switch from glassy plastic to viscoplastic polymer; 2) prominent modulation of viscoplasticity under light illumination at different wavelengths. Regionally selective multiple nanopatterns are conveniently fabricated, presenting angle-dependent structural color images on poly(ethylene terephthalate) (PET) substrates. The flexible, athermal and multiple nanopatterning method has the potential for on-demand fabrication of complex nanopatterns.     

Biocatalytic Feedback-Controlled Non-Newtonian Fluids

Non-Newtonian fluids are ubiquitous in daily life and industrial applications. Herein, we report an intelligent fluidic system integrating two distinct non-Newtonian rheological properties mediated by an autocatalytic enzyme reaction. Associative polyelectrolytes bearing a small amount of ionic and alkyl groups are engineered: by carefully balancing the charge density and the hydrophobic effect, the polymer solutions demonstrate a unique shear thickening property at low pH while shear thinning at high pH. The urea-urease clock reaction is utilized to program a feedback-induced pH change, leading to a strong upturn of the nonlinear viscoelastic properties. As long as the chemical fuel is supplied, two distinct non-Newtonian states can be achieved with a tunable lifetime span. As a proof of concept, we demonstrate how the physical energy-driven nonequilibrium properties can be manipulated by a chemical-fueled process.     

Shear-induced nonisothermal crystallization of two grades of PLA

Shear-induced nonisothermal crystallization of two commercial polylactides (PLAs) differing in optical purity was studied. The molten polymers were sheared at selected temperatures (T_s) and subsequently cooled. The crystallization was followed by a light depolarization method, whereas the specimens were analysed ex-situ by DSC, 2D-WAXS and SEM after etching. It was found that the effect of shear, especially on the crystallinity developed during post-shearing cooling, intensified with a decrease of T_s from 160 to 146 ^°C, and with increasing shear rate and strain. Moreover, the effect of shear on PLA1.5 with d-lactide content of 1.5% was stronger than PLA2.8 with 2.8% of d-lactide, although maximum crystallinity of both polymers was practically the same. A decrease of cooling rate from 30 to 10 ^°C/min increased crystallinity of both PLAs, except for those shearing conditions which induced high crystallinity even during faster cooling. Although SEM examination revealed some row-nucleated forms, no significant crystal orientation was detected by 2D-WAXS, indicating that, under the experimental conditions, the shear induced predominantly point-like nuclei.