The formulation of functional polymers, like adhesives and coatings, is particularly challenging due to the interplay between performance and processability requirements. Polyelectrolyte complexation is an entropically-driven, associative phase separation that results in a polymer-rich coacervate, and a polymer-poor supernatant. Polyelectrolyte complexation can be used in the self-assembly of a range of responsive, bioinspired materials ranging from dehydrated thin films, fibers, and bulk solids to dense, polymer-rich liquid complex coacervates. Salt-driven plasticization allows for the use of polyelectrolyte complexation as an aqueous, polymer processing strategy. However, it is not clear whether many of the heuristics associated with traditional polymers, such as molecular weight and glass transition temperature effects, will apply for materials based on polyelectrolyte complexation (PECs). To understand this design space, we tested a library of PECs made from oppositely-charged methacrylate copolymers of varying charge density, hydrophobicity, and chain length. We characterized the phase behavior and mechanical properties of the resulting liquid coacervates and solid PECs. Our data shows that copolymer chemistry can be used to tune the composition and subsequent viscoelasticity of both solid and liquid materials. Furthermore, the solid-state mechanics can range from brittle to ductile and are intrinsically tied to the water content of the PEC, with copolymer chemistry affecting the amount of water uptaken at a given condition. Lastly, we also characterized the glass transitions of PECs and show that they are coupled to both water content and temperature, creating a glass transition line that can be modulated by tuning both environmental conditions and polymer chemistry.

Artificial tears are essential for managing dry eye syndrome, yet their rheological behavior under physiological conditions remains insufficiently characterized. While previous studies have demonstrated the feasibility of using passive microrheology to assess the viscoelastic properties of human and artificial tears, showing that relaxation times and viscosities depend strongly on hyaluronic acid content and molecular weight [1], a deeper understanding of their response to high deformation rates is still needed.
In this work, we combine rotational rheometry, microfluidic flow experiments, and capillary extensional rheometry to examine both shear and extensional properties of artificial tears, with a focus on mimicking in vivo conditions. Flow curve measurements reveal shear-thinning behavior across physiologically relevant shear rates, while microrheology provides insights into microstructural dynamics. Extensional rheology tests highlight significant differences in elongational viscosity and extensional relaxation time, key parameters for tear film stability and breakup.
Our findings reinforce the idea that extensional properties, often overlooked in artificial tear design, are critical for ensuring optimal performance during blinking. By integrating multiple rheological techniques, this study provides a robust framework for improving artificial tear formulations, moving beyond simple viscosity measurements to achieve better ocular hydration and patient comfort.

Plant-derived foods are complex systems comprising three major macronutrients (starch, protein and fatty acids), which provide energy and nutrients for human nutrition.¹ The interactions between these macronutrients during the manufacturing process are very challenging to define in terms of quality attributes including flavour, smoothness, texture, mouthfeel and digestibility.² The molecular interactions are principally based on electrostatic forces, hydrogen bond formation, Van-der-Waals forces and hydrophobic interactions.³ The behaviour of binary complexes (starch-protein) is influenced by environmental factors, including pH, ionic strength and temperature.³
The objective of this study was to investigate the effect of pH and heating temperature on the viscoelastic properties of the ternary complex in the pH range between 2 and 7. The ternary complex was synthesised through the interaction of carboxymethylated starch (CMS), fatty acids (FA) of varying hydrocarbon chain lengths (C12:0, C14:0 and C16:0), and sacha inchi protein (SI) at a constant weight ratio of 20:2:2 (w/w/w). CMS of varying degrees of substitution (DS=0, 0.25, 0.5, 1) was used as a model to study the influence of carboxylate on the pH-dependent viscoelastic behaviour of CMS-FA-SI mixtures. Model calculations for species distribution of dissociating functional groups explain pH-dependent complex formation (Figure 1). The present study employed a range of analytical techniques, including rheology, DSC and XRD, with a view to elucidating the formation and dissolution of a ternary complex in a pH-dependent environment.

Stimuli-responsive microgels with a well-controlled size and structure are of great interest not only in fundamental research but also in a broad range of applications. [1,2] In this context, we synthesized supramolecular poly(N-isopropylacrylamide) (PNIPAM) microgels by incorporating a home-made metallosupramolecular crosslinker (SC) into the network. To successfully incorporate this positive highly hydrophilic crosslinker during the precipitation polymerization synthesis, we developed a new trick that could be generalized to other monomers incorporation. [3] In addition, the spatial distribution of SC can be drastically tuned by varying the synthesis conditions. Thus, “ultra” core-shell microgels are obtained by batch synthesis conditions, while more homogeneous structures are obtained by a continuous feeding of SC. We show that SC is a powerful tool to quantitatively characterize the microgels structure, with laboratory techniques instead of SANS or SAXS techniques. [4]

The microgels exhibit salt responsiveness benefiting from the crosslinker charges, in addition to temperature responsive properties as expected from PNIPAM-based objects. Besides, these microgels can be disassembled on demand since SCs are cleavable by oxidation, as proven by the disappearance of the characteristic SC pink color. The kinetics of SC cleavage (probed by UV-Visible spectroscopy), the kinetics of microgel disassembly (probed by light scattering measurements) and the mass distribution of the polymer chains resulting from the microgel disassembly (analyzed by Size Exclusion Chromatography) are correlated to the microgel initial structure.

Self-healing is a fascinating natural process that scientists endeavour to mimic as a part of cutting-edge research and development of material science and engineering. In this work, multi-stimuli responsive shape memory-assisted self-healing thermoplastic elastomeric materials are designed by incorporating Fe3O4 particles in dynamically vulcanized thermoplastic elastomeric materials based on thermoplastic polyurethane (TPU)/epoxidized natural rubber (ENR) blends. A thermodynamic perspective is employed to predict the potential distribution of Fe3O4 in the developed blends in which Fe3O4 is selectively distributed in the ENR phase. Interestingly, the Fe3O4-loaded TPV exhibited multi-stimuli responsive shape memory-assisted self-healing functionality, more specifically in the presence of an alternating magnetic field, infrared light, and heat. The resulting dynamically vulcanized TPU/ENR/Fe3O4 blends demonstrated healing efficiencies of ≈53%, ≈78%, and ≈69% under oven heat, under a magnetic field, and under infrared light exposure, respectively. Thermal image mapping is used to understand the stimulus-dependent healing mechanisms. The developed Fe3O4-filled dynamically vulcanized TPV also shows excellent shape memory properties with a shape recovery ratio in the range of 88%–90% under the aforementioned conditions. The incorporation of Fe3O4 possibly induces coordination interactions with zinc dimethacrylate (ZDMA), used as a coagent during dynamic vulcanization, as evidenced by FTIR and XRD analyses, thereby enhancing the functional properties of the developed TPVs. This work provides a unique pathway for the creation of next-generation stimuli-responsive TPE materials that can be applied in smart seals, dynamic implants, soft matter engineering, etc.