Proton Conductive Membranes from Covalently Cross-Linked Poly(Acrylate)/Silica Interpenetrating Networks

The preparation of hybrid proton conductive membranes that comprise of covalently linked interpenetrating polymer and inorganic networks is reported. The hybrid membranes are synthesized via simultaneous photo-initiated polymerization and sol–gel processing. The simultaneous processing permeates fabrication of the membranes that comprises covalently cross-linked polymeric and inorganic networks. The membranes are characterized by attenuated total reflectance-Fourier transform infrared spectroscopy, scaning electron microsopy, thermogravimetric analysis, differential scanning calorimetry, in order to confirm their chemical composition, structure, and morphology. An addition of 3-methacryloxypropyl trimethoxysilane into the sol–gel composition allows the formation of covalent linkages between polymeric and inorganic networks, which facilitates a uniform distribution of the molecular components across the fabricated membranes. The incorporation of the silica network leads to an increase in water retention and proton conductivity of hybrid membranes as compared to their purely polymeric analogues.     

Thermodynamic modeling and experimental investigation of the MgO-Y2O3-ZrO2 system

Solid-state phase equilibria in the MgO-Y₂O₃-ZrO₂ system as well as the equilibria including liquid were investigated in the whole-compositional range using high-temperature differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM/EDX). Isothermal sections at 1493, 1573, 1693, and 1923 K were constructed based on experimental studies. The presence of tie line between MgO and Y₄Zr₃O₁₂ in the temperature range between 1493 and 1573 K was confirmed. The eutectic melting in the MgO-Y₂O₃-ZrO₂ system was established using DTA followed by SEM/EDX microstructure investigation. Based on the obtained experimental results, the thermodynamic database was derived.     

Toward the Prediction and Control of Glass Transition Temperature for Donor–Acceptor Polymers

Semiconducting donor–acceptor (D–A) polymers have attracted considerable attention toward the application of organic electronic and optoelectronic devices. However, a rational design rule for making semiconducting polymers with desired thermal and mechanical properties is currently lacking, which greatly limits the development of new polymers for advanced applications. Here, polydiketopyrrolopyrrole (PDPP)‐based D–A polymers with varied alkyl side‐chain lengths and backbone moieties are systematically designed, followed by investigating their thermal and thin film mechanical responses. The experimental results show a reduction in both elastic modulus and glass transition temperature (T_g) with increasing side‐chain length, which is further verified through coarse‐grained molecular dynamics simulations. Informed from experimental results, a mass‐per‐flexible bond model is developed to capture such observation through a linear correlation between T_g and polymer chain flexibility. Using this model, a wide range of backbone T_g over 80 °C and elastic modulus over 400 MPa can be predicted for PDPP‐based polymers. This study highlights the important role of side‐chain structure in influencing the thermomechanical performance of conjugated polymers, and provides an effective strategy to design and predict T_g and elastic modulus of future new D–A polymers.     

Inherent Photodegradability of Polymethacrylate Hydrogels: Straightforward Access to Biocompatible Soft Microstructures

Hydrogels are important functional materials useful for 3D cell culture, tissue engineering, 3D printing, drug delivery, sensors, or soft robotics. The ability to shape hydrogels into defined 3D structures, patterns, or particles is crucial for biomedical applications. Here, the rapid photodegradability of commonly used polymethacrylate hydrogels is demonstrated without the need to incorporate additional photolabile functionalities. Hydrogel degradation depths are quantified with respect to the irradiation time, light intensity, and chemical composition. It can be shown that these parameters can be utilized to control the photodegradation behavior of polymethacrylate hydrogels. The photodegradation kinetics, the change in mechanical properties of polymethacrylate hydrogels upon UV irradiation, as well as the photodegradation products are investigated. This approach is then exploited for microstructuring and patterning of hydrogels including hydrogel gradients as well as for the formation of hydrogel particles and hydrogel arrays of well‐defined shapes. Cell repellent but biocompatible hydrogel microwells are fabricated using this method and used to form arrays of cell spheroids. As this method is based on readily available and commonly used methacrylates and can be conducted using cheap UV light sources, it has vast potential to be applied by laboratories with various backgrounds and for diverse applications.     

The MgO–TiO2–SiO2 system: Experiments and thermodynamic assessment

Phase relations in the MgO–TiO₂–SiO₂ system have been investigated in air over a wide temperature range using the equilibration method. X-ray powder diffraction, scanning electron microscopy combined with wave length X-ray spectroscopy (SEM/EPMA), and differential thermal analysis (DTA) have been used for sample characterization. Based on the obtained experimental results, isothermal sections of the system at 1523, 1673, and 1773 K have been established. The solid-state invariant reaction MgTi₂O₅ + T-SiO₂⇋P-MgSiO₃ + TiO₂ has been detected at 1625 ± 8 K by step-wise heat treatment. A partial liquidus projection has been suggested, and the temperatures and compositions of three eutectic invariant reactions have been experimentally measured by DTA and ex-situ analysis of the sample microstructures after melting using SEM/EPMA. Considering the newly obtained experimental data, thermodynamic parameters describing the system have been thermodynamically evaluated within the CALPHAD approach.     

A Nanoparticle Ink Allowing the High Precision Visualization of Tissue Engineered Scaffolds by MRI (Small 30/2023)

Hydrogels are widely used as cell scaffolds in several biomedical applications. Once implanted in vivo, cell scaffolds must often be visualized, and monitored overtime. However, cell scaffolds appear poorly contrasted in most biomedical imaging modalities such as magnetic resonance imaging (MRI). MRI is the imaging technique of choice for high-resolution visualization of low-density, water-rich tissues. Attempts to enhance hydrogel contrast in MRI are performed with “negative” contrast agents that produce several image artifacts impeding the delineation of the implant's contours. In this study, a magnetic ink based on ultra-small iron oxide nanoparticles (USPIONs; <5 nm diameter cores) is developed and integrated into biocompatible alginate hydrogel used in cell scaffolding applications. Relaxometric properties of the magnetic hydrogel are measured, as well as biocompatibility and MR-visibility (T₁-weighted mode; in vitro and in vivo). A 2-week MR follow-up study is performed in the mouse model, demonstrating no image artifacts, and the retention of “positive” contrast overtime, which allows very precise delineation of tissue grafts with MRI. Finally, a 3D-contouring procedure developed to facilitate graft delineation and geometrical conformity assessment is applied on an inverted template alginate pore network. This proof-of-concept establishes the possibility to reveal precisely engineered hydrogel structures using this USPIONs ink high-visibility approach.