arXiv subjects

Domenico Truzzolillo

Publications and source records attributed to Domenico Truzzolillo.

At least 19 recordsLinked to original sources

arXiv2026

Universal scalings and switching entropy in yield-stress fluids

Yield-stress fluids transition from solid-like to liquid-like behavior at a critical stress threshold, governing phenomena from industrial processing to geological flows. While predominantly investigated under steady shear, large-amplitude oscillatory tests force these materials to cyclically navigate between arrested and fluidized states. Here, we discover a hidden universal behavior where the dynamic viscoelastic moduli of yield-stress fluids collapse onto master curves, revealing that these materials rearrange almost instantaneously to maintain a constant intra-cycle stress state. We fully capture this behavior using a novel theoretical framework based on the minimization of a governing function that exhibits symmetry breaking. Our findings reveal that recoverable elastic energy, yielding abruptness, and entropy production during stress inversion are fundamentally intertwined. This connection provides a unified physical picture for the dynamic yield stress, offering a novel thermomechanical foundation to define and predict this threshold across soft matter physics and materials science.

cond-mat.soft↗

arXiv2026

Controlling microgel morphology and swelling behavior by copolymerization

The thermosensitive behavior of microgel particles suspended in solvents, i.e. their temperature-dependent swelling properties, has triggered ongoing interest in industry and academia over the past forty years. The most-studied polymer is poly(N-isopropylacrylamide) - PNIPAM -, where the volume phase transition temperature is well known to depend on the detailed molecular architecture of the monomers. In this article, we focus on publications mostly of the past five years in chemical synthesis, aiming at shifting or controlling the volume phase transition temperature (VPTT) of such polymers by copolymerization of a main monomer - often from the PNIPAM family - with either monomers of different hydrophobicity, or with ones bearing ionizable groups. In some cases, hydrophobicity may be modulated by light as external switching parameter, whereas ionic strength or pH may act on the thermosensitivity of the microgels containing charged groups. Due to either differences in reactivity, or specific synthesis routes, particular microgel morphologies, such as molecular gradient, core-shell, interpenetrated, or patchy (multi-lobular) structures may be generated. They may give rise to spatial modulations of thermosensitivity within particles and are highlighted in this review. Our short overview shows that multiple external control of VPTT and morphology is commonly achieved nowadays.

cond-mat.soft↗

arXiv2026

Phase behavior of thermoresponsive colloids drives re-entrant plasmon coupling

Plasmonic nanoparticles (NPs) integrated within thermoresponsive polymeric microgels provide a versatile platform for the realization of stimuli-responsive optical materials, where the microgel volume phase transition enables dynamic control of plasmon coupling. This study uncovers a counter-intuitive re-entrant behavior with increasing NP loading in which plasmon coupling initially strengthens and subsequently weakens beyond a critical NP-to-microgel number ratio. By combining light and X-ray scattering techniques with optical spectroscopy and electrophoretic mobility measurements, it is demonstrated that plasmon coupling is governed not only by the interparticle distance between NPs confined within individual microgels, but also by the colloidal stability of the hybrid complexes. At intermediate NP loadings, surface charge inhomogeneities induced by NP adsorption promote aggregation of microgel-NPs complexes, resulting in enhanced plasmon coupling. In contrast, when the complexes remain colloidally stable, coupling is dictated solely by NP organization within the corona of individual microgels. A quantitative relationship between plasmon coupling and interparticle distance reveals two distinct coupling regimes. This behavior is rationalized through a phase diagram linking colloidal stability to optical response. These findings identify colloidal stability as a key parameter for designing soft plasmonic systems with programmable optical properties.

cond-mat.soft↗

arXiv2025

Smart copolymer microgels with high volume phase transition temperature: Composition, swelling, and morphology

The thermosensitivity and microstructure of microgels made by copolymerizing standard microgel-forming monomers with more hydrophilic comonomers is investigated, with the aim of increasing the volume phase transition temperature (VPTT). We precisely determine the incorporation of N-(hydroxymethyl)acrylamide (HMAM) and purpose-synthesized N-(2-hydroxyisopropyl)acrylamide (HIPAM) into microgels -- neither of which forms microgels on its own by precipitation polymerization. The swelling properties and microstructure of the resulting copolymer microgels with N-isopropylacrylamide (NIPAM, LCST ca. 32°C) and N-isopropylmethacrylamide (NIPMAM, LCST ca. 44°C) are then characterized via turbidimetry, DLS, and AFM. At low comonomer contents, all microgel particles exhibit moderate growth in size. Beyond a system-specific threshold, we observe a significant jump in size, and smoother swelling behavior. For NIPAM-HIPAM, the size increase is linked to a strong rise in swelling capacity, and the formation of a thick corona. The effect of the hydrophilic comonomers on the VPTT correlates linearly with their true composition, allowing us to extrapolate the VPTT of hypothetical pure HMAM and HIPAM microgels. This leads to 99°C for HMAM, and 68°C for HIPAM for the respective VPTT. These numbers can be seen as useful indicators of the effect of these monomers on the VPTT in the copolymerized microgels. The observed changes in VPTT, swelling, size, and morphology suggest that high-VPTT microgels possess unique internal molecular composition gradients, likely due to hydrophobic interactions during synthesis. Our results have potential implications for developing temperature-sensitive microgel-based membranes that can self-adapt their permeability at higher operating temperatures in energy applications.

cond-mat.soft↗

arXiv2025

Linking structure and optical properties of plasmonic nanoparticles on tunable spherical surfaces

The complexation of plasmonic nanoparticles (NPs) and thermoresponsive microgels is widely exploited for applications, but a microscopic description of the mechanisms governing the spatial organization of the NPs is still lacking. Combining small angle X-ray scattering, state-of-the-art simulations and a simple toy model, we uncover how the volume phase transition of microgels controls NP-NP interactions, establishing for the first time a microscopic link between plasmon coupling and NP local structure. Our study paves the way to experimentally investigate phase transitions on controlled curved surfaces at the nanoscale.

cond-mat.soft↗

arXiv2025

Water-in-water PEG/DEX/protein microgel emulsions: effect of microgel particle size on the rate of emulsion phase separation

Protein nanoparticles have been proven to be highly effective stabilizers of water-in-water emulsions obtained from a number of different types of aqueous two-phase systems (ATPS). The stabilizing efficiency of such particles is attributed to their affinity to the water/water interface of relevant ATPS, and emulsion formulations with long-term stability were reported in the recent years. In this study we investigated the macroscopic dynamics of the early-stage time evolution of dextran-in-polyethylene glycol emulsions obtained from a single ATPS and containing beta-lactoglobulin microgel particles of various diameters (ca. 40-190 nm). The results revealed the existence of a threshold in microgel size above which the water-in-water emulsion is stabilized, and that the process of segregative phase separation is determined by the interplay of droplets coalescence and sedimentation. Efficient droplet coalescence inhibition was found for microgel particles larger than 60 nm. Based on previous literature results, we discuss our coalescence-driven phase separation data in the context of the formation of durable particle layers on the emulsion droplets and the resulting droplet-droplet interactions.

cond-mat.soft↗

arXiv2025

Emergent scales and spatial correlations at the yielding transition of glassy materials

Glassy materials yield under large external mechanical solicitations. Under oscillatory shear, yielding shows a well-known rheological fingerprint, common to samples with widely different microstructures. At the microscale, this corresponds to a transition between slow, solid-like dynamics and faster liquid-like dynamics, which can coexist at yielding in a finite range of strain amplitudes. Here, we capture this phenomenology in a lattice model with two main parameters: glassiness and disorder, describing the average coupling between adjacent lattice sites, and their variance, respectively. In absence of disorder, our model yields a law of correspondent states equivalent to trajectories on a cusp catastrophe manifold, a well-known class of problems including equilibrium liquid-vapour phase transitions. Introducing a finite disorder in our model entails a qualitative change, to a continuous and rounded transition, whose extent is controlled by the magnitude of the disorder. We show that a spatial correlation length $ξ$ emerges spontaneously from the coupling between disorder and bifurcating dynamics. With vanishing disorder, $ξ$ diverges and yielding becomes discontinuous, suggesting that the abruptness of yielding can be rationalized in terms of a lengthscale of dynamic heterogeneities.

cond-mat.soft↗

arXiv2025

Emergence of capillary waves in miscible co-flowing fluids

We show that capillary waves can exist at the the boundary between miscible co-flowing fluids. We unveil that the interplay between transient interfacial stresses and confinement drives the progressive transition from the well-known inertial regime, characterized by a frequency independent wavenumber, $k\simω^{0}$, to a capillary wave scaling, $k\simω^{2/3}$, unexpected for miscible fluids. This allows us to measure the effective interfacial tension between miscible fluids and its rapid decay on time scales never probed so far, which we rationalize with a model going beyond square-gradient theories. Our work potentially opens a new avenue to measure transient interfacial tensions at the millisecond scale in a controlled manner.

physics.flu-dyn↗

arXiv2023

Toward a unified description of the electrostatic assembly of microgels and nanoparticles

The combination of soft responsive particles, such as microgels, with nanoparticles (NPs) yields highly versatile complexes of great potential for applications, from ad-hoc plasmonic sensors to controlled protocols for loading and release. However, the assembly process between these microscale networks and the co-dispersed nano-objects has not been investigated so far at the microscopic level, preempting the possibility of designing such hybrid complexes a priori. In this work, we combine state-of-the-art numerical simulations with experiments, to elucidate the fundamental mechanisms taking place when microgels-NPs assembly is controlled by electrostatic interactions. We find a general behavior where, by increasing the number of interacting NPs, the microgel deswells up to a minimum size, after which a plateau behavior occurs. This occurs either when NPs are mainly adsorbed to the microgel corona via the folding of the more external chains, or when NPs penetrate inside the microgel, thereby inducing a collective reorganization of the polymer network. By varying microgel properties, such as fraction of crosslinkers or charge, as well as NPs size and charge, we further show that the microgel deswelling curves can be rescaled onto a single master curve, for both experiments and simulations, demonstrating that the process is entirely controlled by the charge of the whole microgel-NPs complex. Our results thus have a direct relevance in fundamental materials science and offer novel tools to tailor the nanofabrication of hybrid devices of technological interest.

cond-mat.soft↗

arXiv2023

Impact of polyelectrolyte adsorption on the rheology of concentrated Poly(N-Isopropylacrylamide) microgel suspensions

We explore the impact of three water-soluble polyelectrolytes (PEs) on the flow of concentrated suspensions of poly(N-isopropylacrylamide) (PNIPAm) microgels with thermoresponsive anionic charge density. By progressively adding the PEs to a jammed suspension of swollen microgels, we show that the rheology of the mixtures is remarkably influenced by the sign of the PE charge, PE concentration and hydrophobicity only when the temperature is raised above the microgel volume phase transition temperature $T_c$, namely when microgels collapse, they are partially hydrophobic and form a volume-spanning colloidal gel. We find that the original gel is strengthened close to the isoelectric point, attained when microgels are mixed with cationic PEs, while PE hydrophobicity rules the gel strengthening at very high PE concentrations. Surprisingly, we find that polyelectrolyte adsorption or partial embedding of PE chains inside the microgel periphery occurs also when anionic polymers of polystyrene sulfonate with high degree of sulfonation are added. This gives rise to colloidal stabilization and to the melting of the original gel network above $T_c$. Contrastingly, the presence of polyelectrolytes in suspensions of swollen, jammed microgels results in a weak softening of the original repulsive glass, even when an apparent isoelectric condition is met. Our study puts forward the crucial role of electrostatics in thermosensitive microgels, unveiling an exciting new way to tailor the flow of these soft colloids and highlighting a largely unexplored path to engineer soft colloidal mixtures.

cond-mat.soft↗

arXiv2022

A unified state diagram for the yielding transition of soft colloids

Concentrated colloidal suspensions and emulsions are amorphous soft solids, widespread in technological and industrial applications and studied as model systems in physics and material sciences. They are easily fluidized by applying a mechanical stress, undergoing a yielding transition that still lacks a unified description. Here, we investigate yielding in three classes of repulsive soft solids, using analytical and numerical modelling and experiments probing the microscopic dynamics and mechanical response under oscillatory shear. We find that at the microscopic level yielding consists in a transition between two distinct dynamical states, which we rationalize by proposing a lattice model with dynamical coupling between neighboring sites, leading to a unified state diagram for yielding. Leveraging the analogy with Wan der Waals's phase diagram for real gases, we show that distance from a critical point plays a major role in the emergence of first-order-like vs second-order-like features in yielding, thereby reconciling previously contrasting observations on the nature of the transition.

cond-mat.soft↗

arXiv2022

The role of charge content in the two-step deswelling of Poly(N-isopropylacrylamide)-based microgels

Poly(N-isopropylacrylamide)-based microgels are soft colloids undergoing a Volume Phase Transition (VPT) close to ambient temperature. Although widely employed for fundamental research and application purposes, the modifications of the microgel internal structure occurring at the VPT are not yet completely understood, especially concerning the role of electrostatics. Here we study in detail, both experimentally and numerically, the effect of the addition of acrylic acid (AAc) co-monomer on the microgel deswelling process. By combining viscosimetry, light scattering and electrophoresis, we show that the progressive addition of AAc increases the microgel mass and suppresses the occurrence of the VPT, progressively shifting the microgel collapse to higher temperatures. Most importantly, it also highly enhances the two-step deswelling of these submicron-sized networks, so that the inner core collapses at temperatures always lower than those marking the transition of the outer corona. These results indicate that a net increase of the charge density mismatch between the bulk and the surface of the microgels takes place. Numerical simulations fully confirm this scenario and clarify the impact of the charge distribution on the two-step deswelling, with mobile counterions efficiently screening the charges within the inner core, while leaving more monomers ionized on the surface. Our work unambiguously shows how electrostatic interactions influence the behavior of thermosensitive microgels in aqueous environment close to the VPT.

cond-mat.soft↗

arXiv2022

Two-step deswelling in the Volume Phase Transition of thermoresponsive microgels

Thermoresponsive microgels are one of the most investigated class of soft colloids, thanks to their ability to undergo a Volume Phase Transition (VPT) close to ambient temperature. However, this fundamental phenomenon still lacks a detailed microscopic understanding, particularly regarding the presence and the role of charges in the deswelling process. Here we fill this gap by combining experiments and simulations to show that the microgel collapse does not happen in a homogeneous fashion, but through a two-step mechanism, entirely attributable to electrostatic effects. The signature of this phenomenon is the emergence of a minimum in the ratio between gyration and hydrodynamic radii at the VPT. Thanks to simulations of several microgels with different cross-linker concentrations, charge contents and charge distributions, we build a unifying master-curve able to predict the two-step deswelling. Our results have direct relevance on fundamental soft condensed matter science and on microgel applications ranging from materials to biomedical technologies.

cond-mat.soft↗

arXiv2022

Mixing-demixing transition and void formation in quasi-2D binary mixtures on a sphere

Motivated by observations of heterogeneous domain structure on the surface of cells and vesicles and by domain formation due to the adsorption of complex molecules onto composite membranes, we consider a minimal quasi 2D-model to describe the structure of binary mixtures on the surface of a spherical particle. We study the effect of miscibility and adsorbing particle (AP) addition on the mixture structure. We define a new scalar quantity, the geodesic mixing parameter $Ξ$, through which we detail the effect of miscibility and the role of preferential affinity of APs with one of the two components of the mixture, distinguishing unambiguously between mixing and demixing solely induced by APs. Finally, by inspecting the distributions of void sizes, we show how void formation is ruled by miscibility and AP-mixture interactions, which control the transition from exponentially-tailed to fat-tailed distributions.

cond-mat.soft↗

arXiv2021

The double-faced electrostatic behavior of PNIPAm microgels

PNIPAm microgels synthesized via free radical polymerization (FRP) are often considered as neutral colloids in aqueous media, although it is well known, since the pioneering work of Pelton and coworkers [Langmuir 1989, 5, 816-818], that the vanishing electrophoretic mobility characterizing swollen microgels largely increases above the lower critical solution temperature (LCST) of PNIPAm, at which microgels partially collapse. The presence of an electric charge has been attributed to the ionic initiators that are employed when FRP is performed in water and that stay anchored to microgel particles. Combining dynamic light scattering (DLS), electrophoresis, transmission electron microscopy (TEM) and atomic force microscopy (AFM) experiments, we show that collapsed ionic PNIPAm microgels undergo large mobility reversal and reentrant condensation when they are co-suspended with oppositely charged polyelectrolytes (PE) or nanoparticles (NP), while their stability remains unaffected by PE or NP addition at lower temperatures, where microgels are swollen and their charge density is low. Our results highlight a somehow double-faced electrostatic behavior of PNIPAm microgels due to their tunable charge density: they behave as quasi-neutral colloids at temperature below LCST, while they strongly interact with oppositely charged species when they are in their collapsed state. The very similar phenomenology encountered when microgels are surrounded by polylysine chains and silica nanoparticles points to the general character of this twofold behavior of PNIPAm-based colloids in water.

cond-mat.soft↗

arXiv2021

Influence of drug/lipid interaction on the entrapment efficiency of isoniazid in liposomes for antitubercular therapy: a multi-faced investigation

Hypothesis. Isoniazid is one of the primary drugs used in tuberculosis treatment. Isoniazid encapsulation in liposomal vesicles can improve drug therapeutic index and minimize toxic and side effects. In this work, we consider mixtures of hydrogenated soy phosphatidylcholine/phosphatidylglycerol (HSPC/DPPG) to get novel biocompatible liposomes for isoniazid pulmonary delivery. Our goal is to understand if the entrapped drug affects bilayer structure. Experiments. HSPC-DPPG unilamellar liposomes are prepared and characterized by dynamic light scattering, $ζ$-potential, fluorescence anisotropy and Transmission Electron Microscopy. Isoniazid encapsulation is determined by UV and Laser Transmission Spectroscopy. Calorimetry, light scattering and Surface Pressure measurements are used to get insight on adsorption and thermodynamic properties of lipid bilayers in the presence of the drug. Findings. We find that INH-lipid interaction can increase the entrapment capability of the carrier due to isoniazid adsorption. The preferential INH-HSPC dipole-dipole interaction promotes modification of lipid packing and ordering and favors the condensation of a HSPC-richer phase in molar excess of DPPG. Our findings highlight the importance of fundamental investigations of drug-lipid interactions for the optimal design of liposomal nanocarriers.

cond-mat.soft↗

arXiv2020

Spinning elastic beads: a route for simultaneous measurements of shear modulus and interfacial energy of soft materials

Large deformations of soft elastic beads spinning at high angular velocity in a denser background fluid are investigated theoretically, numerically, and experimentally using millimeter-size polyacrylamide hydrogel particles introduced in a spinning drop tensiometer. We determine the equilibrium shapes of the beads from the competition between the centrifugal force and the restoring elastic and surface forces. Considering the beads as neo-Hookean up to large deformations, we show that their elastic modulus and surface energy constant can be simultaneously deduced from their equilibrium shape. Also, our results provide further support to the scenario in which surface energy and surface tension coincide for amorphous polymer gels.

cond-mat.soft↗

arXiv2020

Ultra-low effective interfacial tension between miscible molecular fluids

We exploit the deformation of drops spinning in a denser background fluid to investigate the effective interfacial tension (EIT) between miscible molecular fluids. We find that for sufficiently low interfacial tension, spinning drops develop dumbbell shapes, with two large heads connected by a thinner central body. We show that this shape depends not only on the density and viscosity contrast between the drop and background fluids, but also on the fluid molecular structure, and hence on the stresses developing at their interface due to different molecular interaction. We systematically investigate the dynamics of dumbbell-shaped drops of water-glycerol mixtures spinning in a pure glycerol reservoir. By developing a model for the deformation based on the balance of the shear stress opposing the deformation, the imposed normal stress on the drop and an effective interfacial tension, we exploit the time evolution of the drop shape to measure the EIT. Our results show that the EIT in water-glycerol systems is orders of magnitude lower than that reported in previous experimental measurements, and in excellent agreement with values calculated via the phase field model proposed in [Phys. Rev. X 6, 041057, 2016].

cond-mat.soft↗