Show Abstract ▼

Abstract: Objectives: Biomimetic hydroxyapatite (HAp)-based composites are promising materials for dental restorations due to their hierarchical structure and similarity to natural dental tissues. This study aims to investigate the three-dimensional crystallographic organization of HAp within nacre-inspired composites and to evaluate how different polymers infiltrations influence the structural orientation. Methods: Nacre-inspired HAp ceramic scaffolds were fabricated via bidirectional freeze-casting and subsequently infiltrated with different polymers, including Polyurethane (PU), Poly(methyl methacrylate) (PMMA), Epoxy, and Urethane dimethacrylate (UDMA). The three-dimensional structural organization and crystallite orientation of these composites were investigated using synchrotron-based 3D SAXS tensor tomography (3D SASTT), complemented by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Results: The results reveal distinct differences in crystallite alignment among the composites. HAp/PU exhibits the highest degree of preferred orientation (∼0.7–0.8), whereas HAp/PMMA and HAp/Epoxy show lower alignment values (∼0.2–0.4). The HAp/UDMA composite displays heterogeneous orientation with localized regions of moderate alignment. SEM and EDX analyses confirm variations in lamellar morphology, polymer infiltration, and porosity distribution across the composites. Significance: These findings demonstrate that 3D SASTT enables quantitative mapping of nanoscale crystallite orientation within bulk biomimetic scaffolds and provides new insights into the hierarchical structure of composites, supporting structural design of advanced dental restorative materials.

Open Access

Show Abstract ▼

Abstract: Reversible addition-fragmentation chain transfer (RAFT) polymerisation-induced self-assembly (PISA) has emerged as a powerful method for the synthesis of well-defined block copolymer nanoparticles in a single step. By exploiting the amphiphilicity of block copolymers, PISA enables the formation of self-assembled structures such as micelles, worms, and vesicles. In this work, RAFT-PISA in methanol was employed to synthesise thermoresponsive nanoparticles, with a focus on understanding the relationship between polymer composition, self-assembly behaviour, and temperature-dependent solvation transitions. The homopolymerisation of diethylene glycol methyl ether methacrylate (DEGMA) was successfully achieved using RAFT solution polymerisation in methanol, with 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid (CPDT) identified as the most effective chain transfer agent (CTA). Using CPDT, macro-CTAs of poly(diethylene glycol methyl ether methacrylate) (PDEGMA), poly(triethylene glycol methyl ether methacrylate) (PTEGMA), and poly(oligoethylene glycol methyl ether methacrylate) (POEGMA) were synthesised and kinetically analysed. All homopolymerisations exhibited first-order kinetics with respect to monomer concentration, demonstrating controlled radical polymerisation behaviour. These macro-CTAs were subsequently chain-extended via RAFT methanolic dispersion polymerisation with methyl methacrylate (MMA), yielding diblock copolymers. While PDEGMA-based diblocks displayed colloidal instability, PTEGMA-b-PMMA and POEGMA-b-PMMA copolymers exhibited improved stability, forming well-defined nanoparticles. Increasing the PMMA block length induced a morphological transition from spherical micelles to vesicles. However, the polymerisation of POEGMA-b-PMMA showed poor RAFT control, resulting in broad molecular weight distributions and heterogeneous particle formation. Further investigations explored the chain extension of PTEGMA macro-CTAs with styrene (Sty) and methyl methacrylate derivatives (MeMBl). The choice of RAFT agent significantly influenced polymerisation control and nanoparticle morphology, with a CPADB-derived PTEGMA macro-CTA enabling improved RAFT control in PTEGMA-b-PSty diblock copolymers. Notably, PTEGMA-b-PMeMBl represented the first reported case of MeMBl incorporation into a diblock copolymer via PISA, yielding nanoparticles with well-defined size distributions. The thermoresponsive behaviour of PTEGMA-b-PMMA nanoparticles was investigated using turbidity measurements, dynamic light scattering (DLS), and nuclear magnetic resonance (NMR) spectroscopy. Results revealed a dual lower critical solution temperature (LCST)- and upper critical solution temperature (UCST)-type transition, dependent on solvent composition and PMMA core size. Crosslinked particles confirmed that solvation of the PMMA core was essential for thermoresponsive behaviour. Small-angle X-ray scattering (SAXS) and nano differential scanning calorimetry (nanoDSC) further validated particle solvation upon heating. The solvent-dependent nature of the phase transition was examined, with methanol identified as the optimal solvent for preserving thermoresponsive properties, whereas higher water content disrupted self-assembly. Overall, this study provides new insights into the RAFT polymerisation of thermoresponsive block copolymers, elucidating the key factors governing colloidal stability, nanoparticle morphology, and solvent-mediated phase transitions. These findings contribute to the broader development of stimuli-responsive polymeric materials for advanced applications.

Open Access

Show Abstract ▼

Abstract: The accumulation of plastics such as polyethylene terephthalate (PET), Nylon 66, and polyurethane (PU) presents an environmental challenge that requires scalable circular solutions. Here, we report photoreforming (PR) of acid-hydrolyzed waste plastics into H2 and value-added products using an acid-stable photocatalyst composed of cyanamide-functionalized carbon nitride integrated with cobalt-promoted molybdenum disulfide (CoMoS2–CNx). Under AM 1.5G irradiation, CoMoS2–CNx yields 0.35 ± 0.02 mmol H2 gcat−1 from PET, increasing to 1.9 ± 0.1 mmol H2 gcat−1 under 405 nm LED (33 mW cm−2) irradiation. In 24 h, Nylon 66 and PU yield 1.0 ± 0.4 and 4.2 ± 0.1 mmol H2 gcat−1, respectively. From stability tests, the catalyst remains active over 11 days, affording up to 40% ethylene glycol conversion, 89% acetic acid selectivity, and a 9.0% quantum yield. Acid hydrolysis, enabled by recycled sulfuric acid from spent lead-acid batteries, underpins technoeconomic viability, indicating profitable solar-driven processing of ton-scale plastic waste.

Open Access

Show Abstract ▼

Abstract: Palladium-loaded phosphine polymers have been designed and used as solid molecular catalysts (SMCs) in telomerization reactions with isoprene and short alcohols. A novel tris-(2-methoxyphenyl)phosphine-based polymer (pTOMPP), previously reported poly triphenylphosphine (pTPP) as well as TPP-based polymers with trigonal and tetragonal linkers were tested either pre-loaded or in-situ-loaded. The novel polymer pTOMPP proved to be an excellent support material during in-situ-loading, outperforming triphenylphosphine based polymers. Surprisingly pre-loaded SMCs resulted in significantly lower activity. XAS studies reveal that the enhanced activity of Pd/pTOMPP is due to the coordination sphere of Pd on the polymer showing a higher contribution of Pd-P bonds forming, whereas XAS spectra of Pd/pTPP show a higher contribution of inactive Pd-acac bonds. Especially pre-loaded polymers show little Pd-P interactions.

Open Access

Show Abstract ▼

Abstract: Designing polymers that combine performance with sustainability remains a critical challenge. Here, we report high-performance elastomers derived from CO2 and biobased monomers that integrate both mechanical toughness and closed-loop chemical recyclability through a single material feature: dynamic metal–ionomer cross-links. These ABA block polymers, synthesized from ε-decalactone, δ-jasmolactone, CO2, and bicyclic epoxides, incorporate abundant and inexpensive metal carboxylates (Na(I), Zn(II), and Al(III)) into the midblock, forming reversible networks that enhance tensile strength by 150% while maintaining high strain at break (>1500%) and elastic recovery (>85%). The same cross-links act as built-in catalysts, enabling energy-efficient depolymerization of both polyester and polycarbonate domains at 200 °C, recovering the original monomers. This dual-function approach advances circular polymer design by combining enhanced performance with efficient, low-energy, closed-loop recycling.