Magneto-Responsive Nanocomposites with a Metal–Ligand Supramolecular Matrix

Abstract

Magneto-responsive nanocomposites are prepared by mixing 1−5 vol % of Fe nanoparticles (NPs) in a metallo-supramolecular network made of poly(n-butyl acrylate) (PnBA) bearing terpyridine side groups and cross-linked by the addition of different amounts of Zn 2+ ions. To have a clear understanding of the stepwise increase of complexity, the thermomechanical behavior of these materials was characterized through shear linear rheology at each step of their preparation. The metallo-supramolecular networks reveal a clear transition from polymer-to network-driven dynamics when passing progressively from low (<0 °C) to high temperature. While terpyridine (TPy)−Zn 2+ complexes are usually treated as independent "stickers", the analysis of our master curves strongly suggests their aggregation. After the addition of 1−5 vol % of Fe nanoparticles within the supramolecular networks, we evidence the presence of TPy−NP bonds, resulting in a hybrid network of much longer relaxation time. Lastly, we combine thermal imaging and induction heating to emphasize the signature of sticker dissociation, offering new technical solutions to deepen our fundamental understanding of supramolecular networks.

Topological Interaction among Molecular Cluster Assemblies Affords Tunable Viscoelasticity

“…14,18,49,50 The OPOSS assembly molecules demonstrate a temperature dependence of α T similar to that of typical supramolecular systems with aggregation of functional units, confirming the critical role of aggregation. 49,50 Basically, the aggregation event gives rise to cooperative dynamics among the structural units and could lead to possible caging dynamics.…”

“…The α relaxation is fitted well by Vogel–Fulcher–Tammann (VFT) functions, while the β and γ relaxations are established through Arrhenius functions (Figure f,g and Figure S16). , Note that the α relaxation of Tri-POSS exhibits temperature-dependent dynamics that is stronger than the rheological behavior of a single OPOSS (OPOSS-vinyl), suggesting the existence of a caging effect among OPOSS units. ,,, The OPOSS assembly molecules demonstrate a temperature dependence of α T similar to that of typical supramolecular systems with aggregation of functional units, confirming the critical role of aggregation. , Basically, the aggregation event gives rise to cooperative dynamics among the structural units and could lead to possible caging dynamics.…”

Mechanistic Understanding of Sticker Aggregation in Supramolecular Polymers: Quantitative Insights from the Plateau Modulus of Triblock Copolymers

“…Concretely, active stickers can dramatically slow down the chain diffusion while keeping the glass transition barely unchanged, providing (low T g ) supramolecular networks with an apparent thermoplastic-elastomer-like mechanical behavior. Beyond quantitative decorrelation, many rheological studies have evidenced qualitative differences regarding the temperature dependence of the two processes: while segmental motions obey William–Landel–Ferry dynamics, supramolecular chain diffusion is well-described by Arrhenius profiles, as expected from non-cooperative physical bond dissociation. , …”

“…Among the vast list of examples, a recent study by the group of Van Ruymbeke has notably evidenced the massive aggregation of terpyridine-ion moieties in a metal–ligand-based supramolecular network, resulting in a strong impact on the rheological properties . The same (unexpected) effect was also evidenced on similar (albeit denser) systems by some of us . Interestingly, while the aggregation of stickers might be seen as an undesired effect, researchers have also tried to control it to tune the properties of materials.…”

“…11 The same (unexpected) effect was also evidenced on similar (albeit denser) systems by some of us. 7 Interestingly, while the aggregation of stickers might be seen as an undesired effect, researchers have also tried to control it to tune the properties of materials. This philosophy was notably adopted by the group of Olsen, where a given number of stickers were progressively concentrated at the chain extremities to generate longer terminal relaxation time.…”