Francesca Nardelli

Although Ca2+-mediated ionotropic gelation of pectin has been extensively investigated, the role of alternative divalent cations in network formation remains poorly understood. Here, homogeneous bulk gelation and diffusion-controlled external gelation were used to investigate the effects of cation identity, molecular architecture, and pectin carboxylate availability on ionotropic gelation. CaCl2, BaCl2, and Ba(OH)2 were compared using isothermal titration calorimetry, rheology, X-ray micro-computed tomography, scanning electron microscopy, and solid-state NMR. Ba2+ exhibited stronger binding than Ca2+, consistent with cooperative supramolecular association, and produced more elastic networks, while Ba(OH)2 further enhanced gel formation through increased pectin carboxylate availability. External gelation generated distinct cation-dependent architectures, ranging from homogeneous porous structures to core−shell and layered morphologies. Solid-state NMR showed that Ca2+ induced a partial transition toward a 21 helix, whereas Ba2+ preserved the native 31 helix while increasing conformational order.

Perfluorinated metal–organic frameworks (MOFs) with MIL-140A topology display metal-dependent adsorption behavior: while the Ce^IV analogue [F4_MIL-140A­(Ce)] exhibits step-shaped CO₂ adsorption isotherms and strong affinity for H₂O, both associated with a concerted structural rearrangement of the linkers, the Zr^IV counterpart [F4_MIL-140A­(Zr)] shows a classical type I CO₂ isotherm with a lower adsorption capacity and only weak affinity for H₂O. A multitechnique approach, including solid-state nuclear magnetic resonance spectroscopy, in situ infrared spectroscopy, and variable temperature powder X-ray diffraction, provided clear evidence that this contrasting behavior arises from the absence of an open metal site on Zr^IV and the inability of Zr^IV to adopt an octacoordinated geometry, which prevent the establishment of strong metal-guest interactions.

Field‐cycling (FC) NMR relaxometry is an ideal tool to investigate multiscale polymer dynamics since it can give access to longitudinal relaxation rates ( R ₁ ( ω )) over a broad Larmor frequency range, which can be further extended by employing the frequency–temperature superposition principle. Applications of FC NMR on elastomers of interest for tire industry (i.e., cis ‐1,4‐polyisoprene, cis ‐1,4‐polybutadiene, and co‐poly [styrene‐butadiene]), aimed to obtain information on segmental and polymer dynamics over different regimes as a function of chain length in polymer melts and in dependence on cross‐linking degree and addition of fillers or additives in rubbers, are here reviewed for the first time. After a brief presentation of theoretical tools used in data analysis, studies on polymer melts at variable temperature are reported allowing theories for polymer dynamics, such as tube reptation and renormalized Rouse models, to be tested in the entanglement regime through characteristic dependences of R ₁ ( ω ) on Larmor frequency. Then, studies on rubbers and elastomer compounds are illustrated, highlighting the effects of curing conditions (i.e., temperature, concentration of sulfur and accelerant), and the presence of reinforcing fillers and additives (e.g., tackifying resins) on segmental dynamics, related to macroscopic properties as glass transition temperature, and on collective polymer dynamics. Issues connected with the application of FC NMR relaxometry to polymeric systems with increasing structural and compositional complexity are critically discussed.

In the pursuit of more sustainable tire technologies, the replacement of petroleum-derived additives with bio-based alternatives has become a key research focus. Tackifying resins, which contribute significantly to tread performance and viscoelastic behavior, are among the additives under evaluation for substitution. In this study, several complementary techniques were applied to styrene–butadiene rubber (SBR) compounds, containing either a natural rosin-based resin (Dertoline) or a petroleum-derived resin (Kristalex) at concentrations ranging from 15 to 45 phr, to investigate the effect of resin on the curing process and on compound properties before and after curing. Solid-state NMR spectroscopy and differential scanning calorimetry revealed intimate mixing between polymer and resin at all concentrations and a slowdown in dynamics with increasing resin content that was more pronounced for Kristalex. Dertoline appeared to hinder effective interactions between carbon black, used as a filler, and SBR, leading to a strong suppression of bound rubber, as evidenced by swelling experiments. Vulcanization kinetics, monitored by moving die rheometer experiments, was affected by the two resins in different manners: Kristalex slowed down curing, while Dertoline accelerated it. Moreover, a marching phenomenon was observed at long curing time for high Dertoline concentrations. Cross-link density, determined by equilibrium swelling, decreased with increasing resin loading. Final mechanical and viscoelastic properties of vulcanized compounds, evaluated by dynamic mechanical analysis and tensile tests, were influenced by both resin type and concentration, showing mechanical plasticization effects and changes in both the elastic and anelastic response. Importantly, the two resins appeared to influence wet grip and rolling resistance differently, highlighting their distinct impact on key performance parameters. These results support the tailored use of bio-based tackifiers in sustainable SBR formulations.

The aim of this work is to prepare and characterize a composite adsorbent comprising the hydrophilic ionic liquid 1-ethyl-3-methylimidazolium acetate [EMIM-Ac] composite supported on mesoporous silica gel for application in adsorption heat storage systems. Water adsorption/desorption isotherms were measured gravimetrically at T = 40, 50, 70 °C across a relative humidity (RH) range of 0–0.8, demonstrating a high adsorption capacity (up to 0.71 g/g at 50 °C and RH = 0.8, for a 50 wt % [EMIM-Ac] loading). Full process reversibility and negligible ad/desorption hysteresis were also verified. Thermal stability of the prepared silica/[EMIM-Ac] composites was confirmed up to approximately T = 200 °C. Structural stability of samples subjected to repeated ad/desorption aging cycles was verified via FT-IR, High-Resolution Solid-State NMR, and Time-Domain NMR spectroscopy. Finally, the thermodynamic analysis based on adsorption experimental data indicated that the silica/[EMIM-Ac] composite is highly suitable for adsorption heat storage, providing a volumetric density of 600–920 MJ/m³ at regeneration temperatures below 100 °C.

Understanding fundamental aspects of the adsorption behaviour of flexible metal-organic frameworks (MOFs) is key to develop improved sorbents for gas separations. The recently reported F4_MIL-140A(Ce) displays cooperative CO2 and H2O adsorption driven by concerted rotation of the aromatic rings of the tetrafluoroterephthalate linkers, giving rise to a step-shaped isotherm. Here, we shed light on the key role played by the degree of fluorination of the linker in such mechanism by synthesising novel Fx_MIL-140A(Ce) (x = 2 or 3) analogues and characterising them by gas sorption analysis, in situ powder X-ray diffraction, solid state nuclear magnetic resonance spectroscopy, in situ infrared spectroscopy and adsorption microcalorimetry. We found that the cooperative CO2 adsorption mechanism is switched off in Fx_MIL-140A(Ce), leading to Langmuir-type CO2 isotherms. Different from F4_MIL-140A(Ce), CO2 adsorption triggers no structural response in Fx_MIL-140A(Ce), due to the reduced steric hindrance of less fluorinated linkers that makes the CeIV open metal sites accessible already at low pressure, with no need for concerted aromatic ring rotation. In contrast, the adsorption of water induces similar cooperative structural rearrangements in Fx_MIL-140A(Ce) and the parent F4_MIL-140A(Ce), suggesting that auxiliary adsorbate-linker interactions play a role in inducing cooperative adsorption.

In the tire industry, tackifying resins are essential ingredients because they modulate green tack and green strength of the uncured rubbers, facilitating their manipulation and preventing creep and tear of the final products

In situ characterisation of the multi-step adsorption-induced breathing behaviour of F₄-MIL-53(Al) unveiled the impact of fluorination on framework flexibility and adsorption properties, offering new insights into dynamic porosity in MOFs.