Single‐Source Precursors For Synthesizing Bifunctional Periodic Mesoporous Organosilicas

A new class of bifunctional periodic mesoporous organosilicas (PMOs) composed of organosilicate building blocks with two different silicon sites have been synthesized from the single‐source bifunctional organosilica precursors tris(triethoxysilylethyl)ethoxysilane and bis(triethoxysilylethyl)diethoxysilane, respectively denoted MT³‐PMO and DT²‐PMO. The synthesis of these PMOs is achieved by the co‐assembly of a triblock‐copolymer Pluronic P123 template with the bifunctional organosilica precursor under acid‐catalyzed and inorganic‐salt‐assisted conditions. After template removal through solvent extraction, the MT³‐PMO and DT²‐PMO so obtained show well‐ordered mesopores and display large pore diameters (6–7 nm) and pore volumes (0.6–0.8 cm³ g^–1) with a narrow pore‐size distribution and high surface areas (700–800 m³ g^–1).     

Water‐Resistant Poly(vinyl alcohol)‐Silica Hybrids through Sol‐Gel Processing

Poly(vinyl alcohol) (PVA)‐silica hybrids with exceptionally reduced solubility in water were synthesized. The hybrid xerogels were fabricated through sol‐gel processing of a mixture of PVA and the acid‐catalyzed silica precursor tetraethoxysilane. The effects of varying ratios of PVA and silica precursor on the surface structure, thermal properties, crystallinity, and solubility of the hybrids were investigated. Unlike the highly water‐soluble nature of PVA, all the hybrids displayed considerably reduced solubility in water. This anomalous behavior of PVA in the hybrids can be attributed to the unavailability of its pendant –OH groups. Water‐resistant PVA‐silica hybrids can find applications in various technologies requiring biocompatible systems that are stable in aqueous environments.     

Porous nanocellulose gels and foams: Breakthrough status in the development of scaffolds for tissue engineering

We report on the latest scientific advances related to the use of porous foams and gels prepared with cellulose nanofibrils (CNF) and nanocrystals (CNC) as well as bacterial nanocellulose (BNC) – collectively nanocelluloses – as biomedical materials for application in tissue regeneration. Interest in such applications stems from the lightweight and strong structures that can be efficiently produced from these nanocelluloses. Dried nanocellulose foams and gels, including xerogels, cryogels, and aerogels have been synthesized effortlessly using green, scalable, and cost-effective techniques. Methods to control structural features (e.g., porosity, morphology, and mechanical performance) and biological interactions (e.g., biocompatibility and biodegradability) are discussed in light of specific tissues of interest. The state-of-the-art in the field of nanocellulose-based scaffolds for tissue engineering is presented, covering physicochemical and biological properties relevant to these porous systems that promise groundbreaking advances. Specifically, these materials show excellent performance for in vitro cell culturing and in vivo implantation. We report on recent efforts related to BNC scaffolds used in animal and human implants, which furthermore support the viability of CNF- and CNC-based scaffolds in next-generation biomedical materials.     

Effect of heat treatment time on local structure of lanthanum-aluminum–gallium-borate xerogels

The aim of this study was to investigate the effect of 850 °C heat treatment time on LaAlGaB₅O₂₄ amorphous xerogel. Structural changes were evidenced by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. If xerogel remains non-crystalline after 5 min treatment, nanocrystallites of LaAl_2.03(B₄O₁₀)O_0.54 type are developed after 15 min treatment and this is the sole crystalline phase preserved by increasing the treatment time up to 24 h. Boron, aluminum and gallium units from amorphous xerogel are drastically changed by crystallization, but they are only slightly affected by increasing the 850 °C treatment from 15 min to 24 h.     

3-n-propyl-1-azonia-4-azabicyclo[2.2.2]octanechloride/silica hybrid polymer. A morphologic study in relation to the organic content

The 3-n-propyl-1-azonia-4-azabicyclo[2.2.2]octanechloride/silica hybrid polymer was synthesized, using the sol-gel method, by varying the organic content. The samples were characterized using infrared spectroscopy (FTIR), scanning electron microscopy (SEM), N₂ adsorption-desorption isotherms and thermogravimetric analysis. The polymer morphology could be controlled by the choice and amount of the organic precursor added. The dispersion of the organic/inorganic phases was shown to be in molecular or nanometric level. The organic content elevation produced a decrease in the surface area and pore volume due to the organic pore blocking effect.