Poly Ethylene Oxide Solutions Research Articles

Elastic contribution of polymeric fluids augments salinity-gradient-induced electric potential across a microfluidic channel

HypothesisHarnessing electrical energy from salinity gradients, particularly for powering micro and nanoscale devices, has become a focal point of recent research attention, due to its renewable and biocompatible nature. Much of the reported research in that direction revolves around optimizing the membrane architecture and the charge distribution to maximize the induced electric potential, with no particular emphasis on the fluid rheology. However, many of the modern miniature systems, typically the bio-inspired ones, concern fluids with complex rheological characteristics, where the results for Newtonian solvents may not trivially apply. Here, we hypothesize that the interplay between interfacial electro-mechanics and the fluid rheology can influence the effectiveness of salinity-gradient-modulated electrokinetics significantly – an aspect that has largely remained overlooked. Theory and experimentsHere we report the first experiments supplemented by a theoretical model that unveil how that the addition of polymers in a solvent modulates the salinity gradient – induced electric potential in a microfluidic channel. Our theoretical framework considers the simplified Phan-Thien Tanner (sPTT) constitutive model, which represents the viscoelastic characteristics of fluids. Experiments were conducted with combined pressure driven and salinity gradient driven flow through microchannel involving dilute solutions of polyethylene oxide (PEO) of different molecular weights and concentrations to successfully validate the theoretical approach. FindingsOur findings indicate that the induced electrical potential increased non-linearly with the saline concentration ratio across the microchannel, as compared traditional linear response. Our results demonstrate how the elasticity of fluid may enable realizing an optimal benefit to this effect, by arresting the viscous resistance and uplifting the elastic response via utilizing polymeric inclusions of high relaxation times. These results provide specific insights on preferential windows of augmenting the induced streaming potential by harnessing the viscoelastic nature of the solution and the imposed salt concentration, bearing critical implications in miniature energy harvesting and desalination technology.

Structural Rheology in the Development and Study of Complex Polymer Materials.

The progress in polymer science and nanotechnology yields new colloidal and macromolecular objects and their combinations, which can be defined as complex polymer materials. The complexity may include a complicated composition and architecture of macromolecular chains, specific intermolecular interactions, an unusual phase behavior, and a structure of a multi-component polymer-containing material. Determination of a relation between the structure of a complex material, the structure and properties of its constituent elements, and the rheological properties of the material as a whole is the subject of structural rheology-a valuable tool for the development and study of novel materials. This work summarizes the author's structural-rheological studies of complex polymer materials for determining the conditions and rheo-manifestations of their micro- and nanostructuring. The complicated chemical composition of macromolecular chains and its role in polymer structuring via block segregation and cooperative hydrogen bonds in melt and solutions is considered using tri- and multiblock styrene/isoprene and vinyl acetate/vinyl alcohol copolymers. Specific molecular interactions are analyzed in solutions of cellulose; its acetate butyrate; a gelatin/carrageenan combination; and different acrylonitrile, oxadiazole, and benzimidazole copolymers. A homogeneous structuring may result from a conformational transition, a mesophase formation, or a macromolecular association caused by a complex chain composition or specific inter- and supramolecular interactions, which, however, may be masked by macromolecular entanglements when determining a rheological behavior. A heterogeneous structure formation implies a microscopic phase separation upon non-solvent addition, temperature change, or intense shear up to a macroscopic decomposition. Specific polymer/particle interactions have been examined using polyethylene oxide solutions, polyisobutylene melts, and cellulose gels containing solid particles of different nature, demonstrating the competition of macromolecular entanglements, interparticle interactions, and adsorption polymer/particle bonds in governing the rheological properties. Complex chain architecture has been considered using long-chain branched polybutylene-adipate-terephthalate and polyethylene melts, cross-linked sodium hyaluronate hydrogels, asphaltene solutions, and linear/highly-branched polydimethylsiloxane blends, showing that branching raises the viscosity and elasticity and can result in limited miscibility with linear isomonomer chains. Finally, some examples of composite adhesives, membranes, and greases as structured polymeric functional materials have been presented with the demonstration of the relation between their rheological and performance properties.

Longitudinal ultrasound measurements of polyethylene oxide across dilute to concentrated aqueous solutions

Measuring the properties of polymer solutions is crucial for understanding fundamental polymer physics. The longitudinal ultrasound measurement method offers a promising technique for characterizing these properties. In this study, we develop a mathematical model to correlate longitudinal ultrasonic signals with the material properties of polyethylene oxide (PEO) from dilute to concentrated aqueous solutions. After applying reflection and diffraction corrections, the accuracy of the measurement results improves to over 97 %. Our findings reveal a positive correlation between the speed of sound, density, and longitudinal modulus with the mass concentration of PEO. Additionally, ultrasonic relaxation analysis reveals that PEO solutions exhibit at least one relaxation process in the frequency range of 3–7 MHz, independent of concentration and molecular weight. Compared to dilute solutions, the relaxation amplitude in concentrated solutions is larger and accompanied by strong nonlinearity, attributed to conformational changes caused by molecular entanglement in concentrated solutions.

Effect of liquid elasticity on transient cavitation bubbles in the tube

We investigate the effect of liquid elasticity on the transient cavitation bubbles confined in a tube both experimentally and theoretically. In experiments, the tube-arrest apparatus is used to generate cavitation bubbles near the tube bottom with various polyethylene oxide solutions. Our experiments show that bubble dynamics, particularly the maximum bubble length, are significantly influenced by liquid elasticity. We establish a double oscillator model for the liquid column to explain the experimental results and predict the bubble dynamics over a broader range. Finally, we propose that the reciprocal of the cavitation number Ca2 and prR/k determine the regimes of the liquid column separation, where pr is the reference pressure, R is tube radius, and k is the “stiffness coefficient” of the liquid column. Our work provides a quantitative scaling of the dynamics of large cylindrical cavitation bubbles in viscoelastic liquids during the transient process.

Heat-treated alginate-polycaprolactone core-shell nanofibers by emulsion electrospinning process for biomedical applications

Fabrication of Core-shell nanofibrous mat which is a promising tool for a wide range of applications in tissue engineering can be developed using water in oil (W/O) or oil in water (O/W) emulsion electrospinning. In this study, for the first time, we fabricated an O/W emulsion-based electrospun core-shell mat using polycaprolactone (PCL) as a core and the blend solution of alginate (Alg) and polyethylene oxide (PEO) as shell material. To achieve a stable core-shell mat, firstly, Alg was modified with heat treatment to decrease the molecular weight of Alg. Then, to improve the chain flexibility of Alg, PEO as a second polymer was added to facilitate its electrospinnability. The different volume ratios of O/W were then fabricated by adding PCL to the Alg-PEO solution to find an optimized emulsion solution. The morphology, swelling, and porosity of the construct were evaluated. At the same time, the mechanical characteristic of fibers was evaluated in both dry and wet conditions. This study also examined cell-scaffold interactions to address the need for a scaffolding material to be suitable for tissue engineering and biomedical applications. Finally, the result exhibited a distinct core-shell structure with better mechanical properties compared to the Alg-PEO.

Continuously tunable separation of light-induced Haematococcus pluvialis using an ultrastretchable, sheath-flow-assisted elasto-inertial microchannel

BackgroundA proportion of Haematococcus pluvialis under the light stress can effectively conduct astaxanthin biosynthesis, leading to the increase in cell size. Although the size is a critical indicator for identifying the astaxanthin-rich H. pluvialis cells, the cut-off size to be separated varies from sample to sample. ResultsHere, we report an ultrastretchable, straight elasto-inertial microchannel with tunable separation threshold to continuously separate the light-induced H. pluvialis cells by size. The symmetrical sheath flows confine the particles to the channel sidewalls, and large particles can cross the interface of viscoelastic fluids to the equilibrium position at the channel centerline. By stretching the microfluidic chip, the medium-sized particles can gradually migrate to the channel centerline in the narrower and longer channel, bringing the tunable separation threshold. Results show that the separation performance of the ultrastretchable microfluidic device is affected by total flow rate, flow rate ratio of sheath to sample, polyethylene oxide (PEO) solution configuration. Lastly, size-tunable separation of light-induced H. pluvialis cells is demonstrated. SignificanceTo the best of our knowledge, this is the first report on cell migration in co-flow configurations in the ultra-stretchable microfluidics. Separation of H. pluvialis is not only a relevant end application in harvesting the astaxanthin-rich species, but the separated populations of highly productive microalgal cells will open a venue for cellular directed evolution.

In situ pulmonary mucus hydration assay using rotational and translational diffusion of gold nanorods with polarization-sensitive optical coherence tomography.

Assessing the nanostructure of polymer solutions and biofluids is broadly useful for understanding drug delivery and disease progression and for monitoring therapy. Our objective is to quantify bronchial mucus solids concentration (wt. %) during hypertonic saline (HTS) treatment in vitro via nanostructurally constrained diffusion of gold nanorods (GNRs) monitored by polarization-sensitive optical coherence tomography (PS-OCT). Using PS-OCT, we quantified GNR translational () and rotational () diffusion coefficients within polyethylene oxide solutions (0 to 3wt. %) and human bronchial epithelial cell (hBEC) mucus (0 to 6.4wt. %). Interpolation of and data is used to develop an assay to quantify mucus concentration. The assay is demonstrated on the mucus layer of an air-liquid interface hBEC culture during HTS treatment. In polymer solutions and mucus, and monotonically decrease with increasing concentration. is more sensitive than to changes above 1.5wt. % of mucus and exhibits less intrasample variability. Mucus on HTS-treated hBEC cultures exhibits dynamic mixing from cilia. A region of hard-packed mucus is revealed by measurements. The extended dynamic range afforded by simultaneous measurement of and of GNRs using PS-OCT enables resolving concentration of the bronchial mucus layer over a range from healthy to disease in depth and time during HTS treatment in vitro.

Memory and scission effects of polymers on the flow regime of polyethylene oxide solutions in continuous abrupt contraction–expansion microchannels with different cavity lengths

This study experimentally observes the flow regimes of polyethylene oxide solutions in continuous, abrupt contraction–expansion microchannels. In dilute solutions (0.5 × 10−3–1.5 × 10−3 wt. %), the effects of flow rate, concentration, and cavity length on flow characteristics in the contraction and expansion parts of each cavity are analyzed, including quantified calculations of normalized vortex lengths and extension rates. The results indicate that polymer memory and scission affect the flow transitions. Memory effects enhance vortex growth and scission weakens flow, and these effects occur continuously within the channel. Increased flow rates and cavity lengths intensify polymer scission, accelerating the transitions from elastic instability to corner vortex, lip vortex, and then to steady vortex-free flows in the contraction parts and from steady vortex-free flows to lip and corner vortices in the expansion parts. The flow-regime transitions for concentrations from 0.01 to 0.4 wt. % for dilute and unentangled semi-dilute solutions at various flow rates are summarized in the Reynolds and Weissenberg number spaces. Polymer chains tend to become entangled in higher-concentration solutions, rendering the solution rigid and inducing complex flow regimes.

Effect of Polymer Adjuvant Type and Concentration on Atomization Characteristics of Nozzle

(1) Background: Various types of adjuvants are added during application to enhance the spraying effect, but most adjuvant formulations are proprietary products, and their exact compositions have not been disclosed. (2) Methods: The spatial distributions of droplet sizes and velocities generated by the atomization of different polymer adjuvants were measured based on the phase Doppler interferometer (PDI) measurement method. The sub-area statistical method was used to quantitatively analyze the droplet characteristics at various points below the nozzle. (3) Results: The polymer (polyethylene oxide (PEO))/associative surfactant (sodium dodecyl sulfate (SDS)) can increase the droplet size and velocity of the solution after atomization by increasing the amount of the polymer/associative surfactant to reduce the equilibrium surface tension of the solution and increase the viscosity. Different concentrations of polymer/associative surfactant atomization produced larger droplet sizes and better uniformity than polymer/non-associative surfactant (polysorbate-20 (Tween20)). At the same position, the relationship between droplet velocities for the three adjuvant combinations was roughly as follows: PEO/SDS solution had the highest velocity, followed by PEO solution, and PEO/Tween20 solution had the lowest velocity. (4) Conclusions: The optimal of droplet size distribution can be achieved by adding appropriate amounts of associative surfactants to polymers.

Cavitation in viscoelastic dilute polymer solutions through a Venturi nozzle

This research experimentally examines the influence of viscoelastic dilute water solutions of polyethylene oxide on Venturi cavitation. Variations in solutions are engineered to manipulate the viscoelastic properties that in turn affect cavitation patterns and attributes. The consequences of viscoelasticity and flow conditions on cavitation are quantified using dimensionless numbers, including the elasticity number (El), the Reynolds number (Re), and the pressure ratio (κ). The experiment identifies three distinct cavitation patterns in the solutions, with their transitions being impacted by alterations in El and κ. As El amplifies, the cavitation bubbles expand and get smoother, and the reentrant jet thickens and amplifies. The behavior of cavitation aligns with the model proposed by Zhang et al. [Phys. Fluids 31, 097107 (2019)], suggesting the critical role of the reentrant jet in the shedding of the cavity cluster. The study also substantiates that the reentrant jet intensifies with ascending El or Re. The collective influence of El, Re, and κ is discovered to shape the cavitation length and shedding frequency of cavity clusters. An increased El or a decreased Re reinforces the vorticity and the reentrant jet, which inevitably leads to a reduction in cavitation lengths and an uptick in the shedding frequency. Conversely, a larger El results in a more gradual response of the bubble to pressure alterations and pronounced rebounds, extending the cavitation length.

Instant mucus dressing of PEO reinforced by chitosan nanofiber scaffold for open wound healing

Dressings seamlessly attached to the open wound bed are necessary for fully unleashing the dressing healing ability, as leaving the voids beneath the dressing poses infection hazards. The present study prepared an instant mucus dressing (IMD) of polyethylene oxide (PEO) reinforced by chitosan (CS) nanofiber scaffold, which formed by immersing PEO/CS nanofiber mat in water. The PEO/CS nanofiber mat were fabricated by the solution blow spinning (SBS) method using PEO and CS mixed solutions. Attenuated total reflection Fourier transform infrared spectroscopy (FTIR-ATR), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and differential scan calorimetry (DSC) analyses indicate that PEO macromolecules formed the most of nanofiber shell due to their lower surface tension while CS macromolecules stayed mainly inside the fiber as the core. When such a PEO/CS nanofiber mat was immersed in water, PEO swelled to form mucus dressing reinforced by CS inside the nanofiber, which was fluidic and able to fully fill the voids on the wound. In vivo rat experiment verified that the dressing significantly accelerated the open wound healing through seamlessly attaching of mucus to the open wound and providing moist environment. The dressings exhibit good platelets and whole blood cells adhesion properties, excellent hemostasis function and no cytotoxicity. This instant mucus dressing provided a new perspective for manufacturing high performance open wound dressings.

Hybrid Electrolyte Based on PEO and Ionic Liquid with In Situ Produced and Dispersed Silica for Sustainable Solid-State Battery

This work introduces the synthesis of hybrid polymer electrolytes based on polyethylene oxide (PEO) and electrolyte solution bis(trifluoromethane)sulfonimide lithium salt/ionic liquid 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (LiTFSI/EMIMTFSI) with in situ produced and dispersed silica particles by the sol–gel method. Conventional preparation of solid polymer electrolytes was followed by desolvation of lithium salt in a polymer matrix of PEO, which, in some cases, additionally contains plasticizers. This one-pot synthesis is an alternative route for fabricating a solid polymer electrolyte for solid-state batteries. The presence of TFSI- reduces the crystallinity of the PEO matrix (plasticizing effect), increases the dissociation and solubility of LiTFSI in the PEO matrix because of a highly delocalized charge distribution, and reveals excellent thermal, chemical, and electrochemical stability. Tetraethylorthosilicate (TEOS) was chosen due to the slow reaction rate, with the addition of (3-glycidyoxypropyl)trimethoxysilane (GLYMO), which contributes to the formation of a silica network. FTIR studies confirmed the interactions between the silica, the polymer salt, and EMIMTFSI. Impedance spectroscopy measurements were performed in a wide range of temperatures from 25 to 70 °C. The electrochemical performance was explored by assembling electrolytes in LiCoO2 (LCO), NMC(811), and LiFePO4 (LFP) coin half-cells. The HPEf15 shows a discharge capacity of 143 mA/g for NMC(811) at 0.1 C, 134 mA/g for LCO, and 139 mA/g for LFP half-cells at 0.1 C and 55 °C. The LFP half-cell with a discharge capacity of 135 mA/g at 0.1 C (safety potential range of 2.8 to 3.8) obtained a cyclability of 97.5% at 55 °C after 100 cycles. Such a type of electrolyte with high safety and good electrochemical performance provides a potential approach for developing a safer lithium-ion battery.

Elasto-inertial microfluidic separation of microspheres with submicron resolution at high-throughput

Elasto-inertial microfluidic separation offers many advantages including high throughput and separation resolution. Even though the separation efficiency highly depends on precise control of the flow conditions, no concrete guidelines have been reported yet in elasto-inertial microfluidics. Here, we propose a dimensionless analysis for precise estimation of the microsphere behaviors across the interface of Newtonian and viscoelastic fluids. Reynolds number, modified Weissenberg number, and modified elastic number are used to investigate the balance between inertial and elastic lift forces. Based on the findings, we introduce a new dimensionless number defined as the width of the Newtonian fluid stream divided by microsphere diameter. The proposed dimensionless analysis allows us to predict whether the microspheres migrate across the co-flow interface. The theoretical estimation is found to be in good agreement with the experimental results using 2.1- and 3.2-μm-diameter polystyrene microspheres in a co-flow of water and polyethylene oxide solution. Based on the theoretical estimation, we also realize submicron separation of the microspheres with 2.1 and 2.5 μm in diameter at high throughput, high purity (>95%), and high recovery rate (>97%). The applicability of the proposed method was validated by separation of platelets from similar-sized Escherichia coli (E.coli).

Elasto-inertial instabilities in the merging flow of viscoelastic fluids.

Many engineering and natural phenomena involve the merging of two fluid streams through a T-junction. Previous studies of such merging flows have been focused primarily upon Newtonian fluids. We observed in our recent experiment with five different polymer solutions a direct change from an undisturbed to either a steady vortical or unsteady three-dimensional flow at the T-junction with increasing inertia. The transition state(s) in between these two types of merging flow patterns is, however, yet to be known. We present here a systematic experimental study of the merging flow of polyethylene oxide (PEO) solutions with varying polymer concentrations and molecular weights. Two new paths of flow development are identified with the increase of Reynolds number: one is the transition in very weakly viscoelastic fluids first to steady vortical flow and then to a juxtaposition state with an unsteady elastic eddy zone in the middle and a steady inertial vortex on each side, and the other is the transition in weakly viscoelastic fluids first to a steady vortical and/or a juxtaposition state and then to a fully unsteady flow. Interestingly, the threshold Reynolds number for the onset of elastic instabilities in the merging flow is not a monotonic function of the elasticity number, but instead follows a power-law dependence on the polymer concentration relative to its overlap value. Such a dependence turns out qualitatively consistent with the prediction of the McKinley-Pakdel criterion.

The Investigation of the Production of Salt-Added Polyethylene Oxide/Chitosan Nanofibers.

The influence of different concentrations of salt-added polyethylene oxide (PEO) on the spinnability of chitosan (CS)/PEO + NaCl blends that could be used as a component part of filters for water treatment or nanofiber membranes as well as for medical applications was investigated in this study. The morphological properties of manufactured nanofibers were analyzed as well. It was determined that an increase of PEO concentration resulted mostly in thin and round nanofibers formed during electrospinning, but the manufacturing process became complex, because many wet fibers reached the collector while spinning. Also, it was noticed that the salt was not dissolved completely in the polymer solutions and some crystals were seen in the SEM images of manufactured fiber mats. However, the addition of salt resulted in lower viscosity and better conductivity of solution and fiber mats as well. The opposite effect was observed as the concentration of PEO was increased. The orientation of produced nanofibers as well as their diameter were analyzed with commercially available software. It was determined that the results obtained by software and microscopically are repeatable. The difference among the results of diameter calculated with software and taken by microscope varied from 0% to approximately 12%. The FTIR analyses indicated that alterations in polymer concentrations or the addition of salt did not induce any discernible changes in the chemical composition or nature of the materials under investigation. The sodium chloride present in the solutions enhanced electrical properties and increased conductivity values more than 50 times for PEO solutions and six times for CS/PEO blend solutions, compared to conductivity values of solutions without salt. To assess the thermal characteristics of the PEO/CS blend nanofibers, measurements using a differential scanning calorimeter (DSC) to determine melting (Tm) and crystallization (Tc) temperatures, as well as specific heat capacities were conducted. These parameters were derived from the analysis of endothermic and exothermic peaks observed in the DSC data. It showed that all produced nanofibers were semicrystalline.

Oil displacement in capillary tubes using viscoelastic fluids

Capillary invasion of liquid is a spontaneous phenomenon that occurs at length scales smaller than the capillary length. By means of capillary action, numerous applications have been developed. We investigate the time-dependent displacement of a Newtonian oil using viscoelastic polyethylene oxide solutions. The setup implies a capillary tube in a horizontal configuration that was partially prefilled with oil. We emphasize the prefilling liquid’s role in the dynamics of the system and show the influence of the displacing liquid’s viscoelastic properties. We find significant changes in the capillary regime as the displacing liquid’s viscoelastic properties change.

Accurate estimation of transport coefficients using time correlation functions without fitting any analytic forms in equilibrium simulations

Transport coefficients, such as the diffusion coefficient and shear viscosity, are important material properties that are calculated in computer simulations. In this study, the criterion for the accurate estimation of viscosity, as an example of transport coefficients, is determined by using the Green-Kubo formula without fitting any analytic forms for the stress decay function. The related algorithm is given by the estimation of the viscosities of polyethylene oxide solutions by using a molecular dynamics simulation for testing. The algorithm can be used in the simulations of complex systems with a long tail of correlations typically found in macromolecular and biological simulation systems.

Photophysical studies of a coumarin derivative in the aqueous solution of three different classes of copolymers

In this article we have reported the modulation of spectral behavior of a hydrophilic coumarin based molecule 7-(diethylamino) coumarin-3-carboxylic acid (7-DCCA) in aqueous solution of polyethylene oxide (PEO)-polypropylene oxide (PPO) block copolymers with different structures and hydrophobicity. Linear triblock copolymer namely Pluronic (F-98, F-38, P-84), its X-shaped counterpart namely Tetronic (T-1304, T-1307) along with a reverse Pluronic (17-R4) were utilised with a temperature variation from 10 °C to 50°C and 7-DCCA was used as the probe to observe the changes in photophysical aspect. Of the studied copolymers, 10 wt% T-1307 and F-38 face difficulty in micelle formation owing to their hydrophilic nature and lower molecular weight PPO blocks. Also, 0.1 wt% 17-R4 remains as single-coils in the studied temperature range. Hence, these copolymers induce a different environment on the photophysics in 7-DCCA as compared to copolymers that form usual micelles (10 wt% T-1304, P-84, F-98). With increasing temperature, a persistent blue-shift in absorption and excitation spectra of the probe could be noticed upon addition of 10 wt% T-1304, T-1307, F-98, P-84, as well as 0.1 wt% 17-R4. The fluorescence emission maximum of the probe blue-shifted in T-1304, T-1307, F-98 and P-84 solutions whereas a red-shift was noticed in 17-R4. The fluorescence emission decays collected in the presence of T-1304, T-1307, F-38, F-98 and P-84 were fitted using tri-exponential functions while bi-exponential functions were used in the presence of 17-R4. A dip-rise-dip anisotropy decay pattern was observed for T-1307, F-38, and 17-R4 whereas, bi-exponential functions were used for T-1304, F-98 and P-84. The constitution of the copolymer along with its molecular properties helped us to correlate the obtained data.

Fine characterization of the capillary instability of free viscoelastic jets

The experimental approach presented in this article investigates low-velocity small-diameter cylindrical viscoelastic jets. It consists in producing and analyzing sets of jet portion images taken at different positions along the jet axis, i.e., from the nozzle producing the jet down to the spray region. A very significant part of the work was dedicated to develop analyzing tools: a proper orthogonal decomposition to identify the onset of the capillary instability, a procedure to determine the mean jet breakup length and a multi-scale tool to describe the jet local shape and its evolution along the jet axis. Used in a similar previous study, the multi-scale analysis has been extended in the present work. These tools are shown to be well suited to the experimental study conducted here, and in particular to meet the need for statistical analysis that free jets impose. They are applied to study the capillary instability of free jets of dilute polyethylene oxide solutions produced from a micrometer nozzle. The parameters of the study are the molar mass of the polymer and the velocity of the jet. Results on the detection of the capillary instability onset, the jet evolution dynamics towards the Bead On A String (BOAS) pattern, the local extensional relaxation time and the terminal elongational viscosity of the solutions, the bead coalescence mechanism and its influence on the size of the spray drops are obtained. Analysis of these results reveals that the polymers undergo two episodes of mechanical degradation during the process: the first one at injection, the second one during the elasto-capillary regime of the jet breakup. Moreover, the scenario in the literature suggesting a sufficiently relaxed axial tension of the flow for the capillary instability to occur is found to be not always valid. It is also shown that the average size of the drops correlates with the intensity of the bead coalescence mechanism that takes place on the BOAS. These results demonstrate the richness of the adopted approach and in particular of the multi-scale analysis to study the development of a fluid interfacial instability.

Linking surface tension to water polarization with a new hypothesis: The Ling-Damodaran Isotherm.

Studying aqueous solutions of complex (bio)polymers is essential from both theoretical and practical perspectives. To understand the principles that govern the properties of these solutions is pivotal for the study of biological processes, considering that the most distinguished components of the cells are polymers (proteins, nucleic acids). These macromolecular aqueous systems, known as colloids, has raise the interest of scientists in recent years. It is known that several physicochemical properties deviate from ideal behaviour in this kind of solutions and that the physical state of water is different compared to its pure state. Particularly, the surface tension of such mixtures often shows a peculiar profile at semi-dilute and concentrated conditions. Here, we joined the colloidal concept of water polarization (proposed in the Association-Induction Hypothesis) with Damodaran's formalism for surface tension to theoretically derive a compelling mathematical model that explains the behaviour of polymer solutions. We measured the surface tension and osmolarity of different polyethylene oxide solutions and we used the ACDAN fluorescence probe to assess the water dipolar relaxation (polarization) in these mixtures. As a proof of concept, we also studied the influence of these polymer solutions on lipid interfaces. Our isotherm model explains the experimental observations with a unifying view that correlates with other measured properties, such as osmolarity and water dipolar relaxation. This provides a link between interfacial and bulk physicochemical properties of polymer solutions, also giving a new framework for studying the interaction of colloidal systems with lipid membranes interfaces.