Thermal Properties and Non-Isothermal Crystallization Kinetics of Poly (δ-Valerolactone) and Poly (δ-Valerolactone)/Titanium Dioxide Nanocomposites

Degradable and Reprocessable Resins from a Dioxolanone Cross-Linker

Chemically cross-linked polymers offer excellent temperature and solvent resistance, but their high dimensional stability precludes reprocessing. The renewed demand for sustainable and circular polymers from public, industry, and government stakeholders has increased research into recycling thermoplastics, but thermosets have often been overlooked. To address this need for more sustainable thermosets, we have developed a novel bis(1,3-dioxolan-4-one) monomer, derived from the naturally occurring l-(+)-tartaric acid. This compound can be used as a cross-linker and copolymerized in situ with common cyclic esters such as l-lactide, ε-caprolactone, and δ-valerolactone to produce cross-linked, degradable polymers. The structure-property relationships and the final network properties were tuned by both co-monomer choice and composition, with properties ranging from resilient solids with tensile strengths of 46.7 MPa to elastomers with elongations up to 147%. In addition to exhibiting properties rivalling those of commercial thermosets, the synthesized resins could be recovered at end-of-life through triggered degradation or reprocessing. Accelerated hydrolysis experiments showed the materials fully degraded to tartaric acid and the corresponding oligomers from 1 to 14 days under mild basic conditions and in a matter of minutes in the presence of a transesterification catalyst. The vitrimeric reprocessing of networks was demonstrated at elevated temperatures, and rates could be tuned by modifying the concentration of the residual catalyst. This work develops new thermosets, and indeed their glass fiber composites, with an unprecedented ability to tune degradability and high performance by creating resins from sustainable monomers and a bio-derived cross-linker.

Mechanical Characteristics and Bioactivity of Nanocomposite Hydroxyapatite/Collagen Coated Titanium for Bone Tissue Engineering

In the present study, we have analyzed the mechanical characteristics and bioactivity of titanium coating with hydroxyapatite/bovine collagen. Hydroxyapatite (HAp) was synthesized from a Pinctada maxima shell and has a stoichiometry (Ca/P) of 1.72 and a crystallinity of 92%, suitable for coating materials according to ISO and Food and Drug Administration (FDA) standards. Titanium (Ti) substrate coatings were fabricated at HAp concentrations of 1% (Ti/HAp-1) and 3% (Ti/HAp-3) and a bovine collagen concentration of 1% (Ti/HAp/Coll) by the electrophoresis deposition (EPD) method. The compressive strength of Ti/HAp-1 and Ti/HAp-3 was 87.28 and 86.19 MPa, respectively, and it increased significantly regarding the control/uncoated Ti (46.71 MPa). Furthermore, the Ti/HAp-coll (69.33 MPa) has lower compressive strength due to collagen substitution (1%). The bioactivity of Ti substrates after the immersion into simulated body fluids (SBF) for 3-10 days showed a high apatite growth (Ca²⁺ and PO43-), according to XRD, FTIR, and SEM-EDS results, significantly on the Ti/HAp-coll.

Photocatalytic water oxidation with a Prussian blue modified brown TiO2

A recently emerging visible light-absorbing semiconductor, brown TiO₂ (b-TiO₂), was coupled with a CoFe Prussian blue (PB) analogue to prepare an entirely earth-abundant semiconductor/water oxidation catalyst hybrid assembly. PB/b-TiO₂ exhibits a sevenfold higher photocatalytic water oxidation activity compared to b-TiO₂. An elegant band alignment unified with the optical absorption of b-TiO₂ and excellent electronic dynamics of PB yield a high-performance photocatalytic system.

Ring-opening copolymerization of ε-caprolactone and δ-valerolactone by a titanium-based metal–organic framework

Copolymerization of ε-caprolactone and δ-valerolactone without any co-catalyst in a solvent-free medium under eco-friendly conditions using earth abundant Ti-metal based MOF, MIL-125.

Integrating adsorption and photocatalysis: A cost effective strategy for textile wastewater treatment using hybrid biochar-TiO2 composite

TiO₂ based photocatalysts are extensively used for textile wastewater treatment as they are ecofriendly, inexpensive, easily available, nontoxic and have higher photostabililty. However, their wider band gap, charge carrier's recombination, and utilization of light absorbance limits their performance. In the present work, a hybrid biochar-TiO₂ composite (BCT) has been synthesized by a facile synthesis strategy to overcome these problems. These photocatalysts are characterized using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), UV-vis diffuse reflectance spectra (DRS), and photoluminescence (PL) to evaluate their crystallinity, morphology, functional groups, bandgap energy and charge separation properties, respectively. The photodegradation of simulated textile wastewater is analyzed using hybrid composites. The hybrid biochar-TiO₂ composite showed higher charge separation, slow recombination of electron-hole pairs, and enhanced light absorption as compared to control (pure TiO₂ and BC alone). 99.20 % photodegradation efficiency of dye-simulated wastewater is achieved employing optimum hybrid composite, while the pure biochar and TiO₂ samples exhibits 85.20 % and 42.60 % efficiencies, respectively. The maximum adsorption capacity is obtained for hybrid biochar-TiO₂ sample, 74.30 mgg^-1 in comparison to biochar (30.40 mgg^-1) and pure TiO₂ (1.50 mgg^-1). The results show that hybrid biochar-TiO₂ composites can perform in the target application of organic industrial pollutant removal.