Mariapaola Staropoli

The development of recyclable epoxy thermosets capable of combining rapid reprocessability with high thermomechanical performance remains a major challenge in vitrimer research. In this work, a systematic structure-property investigation of self-catalyzed transesterification (TER)-based epoxy-amine vitrimers was carried out using commercially available ester-containing diglycidyl monomers and a broad range of amine hardeners to establish molecular design principles for this family of materials. A series of structurally analogous model networks was first designed to elucidate the influence of ester structure and amine chemistry on vitrimer dynamics, stress relaxation, and thermomechanical behavior. The results demonstrate that cycloaliphatic amines generate highly active tertiary amine catalytic centers in situ, resulting in substantially faster stress relaxation than analogous aromatic amines, while aromatic diglycidyl ester monomers simultaneously enhance Tg, modulus, and long-term thermal stability. In addition, the direct attachment of ester groups to aromatic rings was found to accelerate transesterification at elevated T (> 170 °C) compared to cycloaliphatic ester analogues, revealing a previously underexplored factor governing vitrimer dynamics. Building on these insights, a broader family of diglycidyl phthalate/aliphatic amine vitrimers was developed and systematically studied. The optimized networks exhibited excellent combinations of thermal, rheological, and mechanical properties, including Tg values up to 134 °C, storage moduli up to 2.7 GPa, Young’s moduli of 3.4–4.2 GPa, tensile strengths up to 92 MPa, and rapid stress relaxation at 180 °C (τ* = 235–745 s), making them promising candidates for structural applications. Optimized materials were successfully mechanically recycled multiple times via hot pressing without detectable loss of performance and demonstrated complete chemical degradation under mild acidic conditions at room temperature.

Sulfide-based solid electrolytes (SEs) are promising enablers of next-generation solid-state batteries (SSBs), yet their practical implementation is limited by interfacial instability with anode and cathode active materials. Current interfacial mitigation strategies rely primarily on inorganic coatings, which are often unable to accommodate chemo-mechanical strain. Here, we introduce a new dynamic ion gel nanocoating that stabilizes both cathode and anode interfaces in sulfide-based SSBs. It is a type of ion-conductive polyelectrolyte complex (PEC), which is formed via complex coacervation between oppositely charged polyelectrolytes. Controlled mixing of a polycation bearing ammonium groups with TFSI– counteranions and a polyanion featuring pendant TFSI– groups with Li+ countercations yields a homogeneous, solution-processable dynamic ion gel accompanied by LiTFSI release. This enables uniform, thin (≈1–3 nm), and scalable PEC nanocoatings on active material particles via spray drying. Dynamic ionic cross-linking endows the PEC with enhanced viscoelasticity and improved ionic conductivity relative to the parent polycation, allowing it to adapt to solid–solid interfaces while maintaining efficient ion transport. SSBs employing PEC-coated silicon anodes and PEC-coated LiNiO2 cathodes exhibit improved cycling stability through suppression of interfacial side reactions. Thus, the PEC nanocoating acts as a scalable stabilizer of solid–solid interfaces in SSBs.

Silica is used as reinforcing filler in the tire industry. Owing to the intensive process of silica production and its high density, substitution with lightweight bio-based micro fibrillated cellulose (MFC) is expected to provide lightweight, sustainable, and highly reinforced tire composite. MFC was modified with oleoyl chloride, and the degree of substitution (DS) was maintained between 0.2 and 0.9. Subsequently, the morphology and crystallinity of the modified MFC were studied and found to be significantly dependent on the DS. The advantages associated with the use of the modified MFC in synergy with silica for the reinforcement of styrene butadiene rubber (SBR) nanocomposite was investigated in comparison with silica/SBR compound. The structural changes occasioned by the DS values influenced the processability, curing kinetics, modulus-rolling resistance tradeoff, and tensile properties of the resultant rubber compounds. We found that the compound made with modified MFC at a DS of 0.67 (MFC16) resulted to the highest reinforcement, with a 350% increase in storage modulus, 180% increase in Young`s modulus, and 15% increase in tensile strength compared to the referenced silica-filled compounds. Our studies show that MFC in combination with silica can be used to reinforce SBR compound for tire tread applications.

In silica-rubber based nanocomposites, a single organo-silicon is often used to compatibilize and covalently link silica to rubber. In this work, we have investigated the impact, at micro- and macroscales, of the decoupling of the hydrophobization and the coupling activity of silane by pretreating silica with two different silane chemistries. The first one, a mercaptosilane, is the coupling agent that promotes a covalent link between silica and rubber during the sulfur-mediated vulcanization reaction. The second one, an alkylsilane, aims to improve the silica dispersion. For both kind of silanes, we have varied the chain length and studied at macroscale the dynamic mechanical properties through the key indicators that are E'' as loss modulus, E' as storage modulus, and their respective ratio tan δ. The shorter silanes combination yielded an improvement in terms of wet grip indicators with tan δ at 0 °C increasing from 0.205 to 0.237 while maintaining rolling resistance indicators at the same level. We have evaluated the impact of the silane chemistry onto the cross-linking reactivity within the fabricated rubber-based nanocomposites by using moving-dye rheometer measurements (MDR). By purposely using atomic force microscopy (AFM), we have studied the silica dispersion in the matrix and the rubber/silica interface and provided the rationale explanation of the mechanical properties observed at the macroscale. AFM observation pointed out the existence of a soft interface around silica fillers when long alkylsilanes were used. We infer that this interface impacts the polymer-filler dynamic and subsequently affects the mechanical properties of the composite material.

The improvement of mechanical properties of polymer-based nanocomposites is usually obtained through a strong polymer–silica interaction. Most often, precipitated silica nanoparticles are used as filler. In this work, we study the synergetic effect occurring between dual silica-based fillers in a styrene-butadiene rubber (SBR)/polybutadiene (PBD) rubber matrix. Precipitated Highly Dispersed Silica (HDS) nanoparticles (10 nm) have been associated with spherical Stöber silica nanoparticles (250 nm) and anisotropic nano-Sepiolite. By imaging filler at nano scale through Scanning Transmission Electron Microscopy, we have shown that anisotropic fillers align only in presence of a critical amount of HDS. The dynamic mechanical analysis of rubber compounds confirms that this alignment leads to a stiffer nanocomposite when compared to Sepiolite alone. On the contrary, spherical 250 nm nanoparticles inhibit percolation network and reduce the nanocomposite stiffness.

We present a structural and dynamic study on the simplest supramolecular hetero-association, recently investigated by the authors to prepare architectural homogeneous structures in the melt state, based on the bio-inspired hydrogen-bonding of thymine/diaminotriazine (thy–DAT) base-pairs. In the combination with an amorphous low T_g poly(butylene oxide) (PBO), no micellar structures are formed, which is expected for nonpolar polymers because of noncompatibility with the highly polar supramolecular groups. Instead, a clear polymer-like transient architecture is retrieved. This makes the heterocomplementary thy–DAT association an ideal candidate for further exploitation of the hydrogen-bonding ability in the bulk for self-healing purposes, damage management in rubbers or even the development of easily processable branched polymers with built-in plasticizer. In the present work, we investigate the temperature range from T_g + 20 °C to T_g + 150 °C of an oligomeric PBO using small-angle X-ray scattering (SAXS) and linear rheology on the pure thy and pure DAT monofunctionals and on an equimolar mixture of thy/DAT oligomers. The linear rheology performed at low temperature is found to correspond to fully closed-state dimeric configurations. At intermediate temperatures, SAXS probes the equilibrium between open and closed states of the thy–DAT mixtures. The temperature-dependent association constant in the full range between open and closed H-bonds and an enhancement of the monomeric friction coefficient due to the groups is obtained. The thy–DAT association in the melt is more stable than the DAT–DAT, whereas the thy–thy association seems to involve additional long-lived interactions.

Scattering techniques with neutrons and X-rays are powerful methods for the investigation of the hierarchical structure of reinforcing fillers in rubber matrices. However, when using only X-ray scattering, the independent determination of the filler response itself sometimes remains an issue because of a strong parasitic contribution of the ZnO catalyst and activator in the vulcanization process. Microscopic characterization of filler-rubber mixtures even with only catalytic amounts of ZnO is, therefore, inevitably complex. Here, we present a study of silica aggregates dispersed in an SBR rubber in the presence of the catalyst and show that accurate partial structure factors of both components can be determined separately from the combination of the two scattering probes, neutrons, and X-rays. A unique separation of the silica filler scattering function devoid of parasitic catalyst scattering becomes possible. From the combined analysis, the catalyst contribution is determined as well and results to be prominent in the correction scheme. The experimental nano-structure of the ZnO after the mixing process as the by-product of the scattering decomposition was found also to be affected by the presence or absence of silica in the rubber mixture, correlated with the shear forces in the mixing and milling processes during sample preparation. The presented method is well suited for studies of novel dual filler systems.