Detection of intestinal parasites in human faecal samples using dissolved air flotation.

OBJECTIVE: Ova and parasite (O&P) examination is recommended for the laboratory diagnosis of agents causing parasitic infections; however, this exam requires scientific and technological improvements to enhance its diagnostic validity. Dissolved air flotation (DAF) is an efficient technical principle separating suspended solids in a liquid medium. We aimed to develop and validate a new procedure for intestinal parasite detection with DAF. METHODS: In this study, we collected samples from 500 volunteers, screened them by direct examination, and transferred the material to tubes using the Three Faecal Test (TF-Test) for triplicate DAF tests. We evaluated physical-chemical parameters and DAF prototype components through quantifying parasites recovered from floated and non-floated regions of the flotation column. The DAF operation protocol was validated with the gold standard results. RESULTS: The 10% saturated volume proportion and cationic surfactant showed regularity and high parasite recovery (80%). Modifications of the needle device did not influence parasite recovery (p > 0.05). Sensitivity, specificity, accuracy and kappa agreement obtained with the DAF protocol were 91%, 100%, 93% and substantial (k = 0.64), respectively. CONCLUSION: The DAF principle could be used to process faecal samples in routine laboratory exams, enabling intestinal parasite detection.

Using inulin-based emulsion gels as fat substitute in salt reduced Bologna sausage.

BACKGROUND: A high-fiber emulsion gel (EG) containing inulin, soy protein isolate, and soybean oil was applied as animal fat replacer in reduced salt and fat Bologna sausage containing mechanically deboned chicken meat, pork meat, and pork back fat. Technological and microbiological properties were evaluated for 60 days at 4 °C. RESULTS: A reduction of 11 to 34% and 35 to 45% of fat and sodium were obtained in reformulated products, respectively. An increase in fiber content and polyunsaturated fatty acid was noticed in the formulations with EG. The addition of EG in Bologna increased L* (lightness) values and reduced a* (redness/greenness) values comparing to control treatment. Microstructural properties of sausages exhibited a denser network with the presence of EG. Softer, more elastic, cohesive and resilient samples with a higher intensity of lipid oxidation (P < 0.05) were observed in EG added sausages. The nuclear magnetic resonance (NMR) data shows that the presence of EG recovers the matrix that has been weakened due to reduction of fat and salt. Sensory evaluation showed that the incorporation of the EGs resulted in acceptable scores. CONCLUSION: These results suggest that inulin-based EG is a potential fat substitute for developing healthier meat products, with better fatty acids composition and stable to chilled storage. © 2020 Society of Chemical Industry.

Light-Triggered Rheological Changes in a System of Cationic Wormlike Micelles Formulated with a Photoacid Generator.

"Smart" fluids displaying large changes in their rheological properties in response to external stimuli have been of great interest in recent years. For example, "smart" wormlike micelles (WLMs) that respond to pH can be readily formulated by combining a cationic surfactant such as cetyltrimethylammonium bromide (CTAB) with an aromatic compound such as 1,2-dihydroxybenzene (DHB). Here, we show that a pH-responsive aqueous formulation as mentioned above can be simultaneously made responsive to ultraviolet (UV) light by incorporating a photoacid generator (PAG) into the system. A commercially available PAG, diphenyliodonium-2-carboxylate, is used here. Upon exposure to UV light, this PAG irreversibly photolyzes into iodobenzene (IB) and benzoic acid (BA), with the formation of BA, leading to a drop in pH. WLMs formed by mixtures of CTAB, DHB, and the PAG are systematically characterized before and after UV irradiation. As the PAG photolyzes, an increase in the viscosity of WLMs occurs by a factor of 1000. We show that the ratio of the zero-shear viscosity η0 (after UV/before UV) depends on the initial pH of the sample. The UV-induced increase in η0 can be attributed to the growth of WLMs in solution, which in turn is influenced by both the ionization state of DHB and the presence of IB and BA.

Use of the aqueous biphasic system as an alternative for concentration of Ascaris lumbricoides eggs, with non-toxic separation of faecal residues and fats.

OBJECTIVES: Human enteroparasites are considered a serious public health problem in underdeveloped countries located in world regions with tropical, subtropical and equatorial climates. These parasites are commonly diagnosed by the Parasitological Examination of Faeces (PEF), performed by conventional techniques and/or commercial kits that result in tests with low-to-moderate sensitivity, due to the use of destructive chemical solvents to parasite structures, and to present excess adipose substance and digestive residues in their microscopic slides. In order to improve the efficacy of these tests/examinations, this study aimed to investigate a new alternative for the PEF, with the use of Aqueous Biphasic System (ABS). METHODS: For this, four ABSs containing poly (ethylene glycol), PEG (PEG-4000 and PEG-6000), dipotassium phosphate and sodium citrate at different concentrations in the biphasic systems were evaluated with faecal samples containing eggs of Ascaris lumbricoides. RESULTS: The ABS consisting of PEG-4000 and dipotassium phosphate, at concentrations of 55% w/w and 20% w/w, respectively, achieved 100% satisfactory results compared to the conventional TF-Test technique in terms of preservation and concentration of A. lumbricoides eggs, with adequate separation of digestive residues, without using a centrifuge or chemical solvents that may cause harm to the parasites. CONCLUSIONS: This study presents ABS as a new low-cost technical principle for the detection of parasite eggs in PEF. The new technique is simple, fast, non-toxic, not harmful to the parasite and does not require a centrifuge.

UTILISATION DU SYSTÈME BIPHASIQUE AQUEUX COMME ALTERNATIVE À LA CONCENTRATION DES ŒUFS D'ASCARIS LUMBRICOIDES, AVEC SÉPARATION NON TOXIQUE DES RÉSIDUS FÉCAUX ET DES GRAISSES: OBJECTIFS: Les entéroparasites humains sont considérés comme un sérieux problème de santé publique dans les pays sous-développés situés dans des régions du monde aux climats tropicaux, subtropicaux et équatoriaux. L'examen parasitologique des matières fécales (EPMF) permet généralement de diagnostiquer ces parasites, à l'aide de techniques classiques et/ou de kits commerciaux, conduisant à des tests de sensibilité faible à modérée, dus à l'utilisation de solvants chimiques destructeurs pour les structures du parasite et résultant en excès de substances adipeuses et de résidus digestifs dans leurs lames microscopiques. Afin d'améliorer l'efficacité de ces tests/examens, cette étude visait à étudier une nouvelle alternative à l'EPMF, avec l'utilisation du Système Biphasique Aqueux (SBA). MÉTHODES: Pour cela, quatre SBA contenant du poly (éthylène glycol), du PEG (PEG-4000 et PEG-6000), du phosphate dipotassique et du citrate de sodium à différentes concentrations ont été évalués avec des échantillons de matières fécales contenant des œufs d'Ascaris lumbricoides. RÉSULTATS: Le SBA constitué de PEG-4000 et de phosphate dipotassique, à des concentrations respectives de 55% poids/poids et 20% poids/poids, a obtenu des résultats satisfaisants à 100% par rapport à la technique conventionnelle du TF-Test, en termes de préservation et de concentration des œufs de A. lumbricoides, avec une séparation adéquate des résidus digestifs, sans utiliser de centrifugeuse ni de solvants chimiques pouvant détruire les parasites. CONCLUSIONS: Cette étude présente le SBA comme un nouveau principe technique peu coûteux pour la détection des œufs de parasites dans l'EPMF. La nouvelle technique est simple, rapide, non toxique, n'endommage pas le parasite et ne nécessite pas de centrifugeuse.

Probing the Formation of Wormlike Micelles Formed by Cationic Surfactant with Chlorobenzoate Derivatives.

The energy released when tetradecyltrimethylammonium bromide (C14TAB) is combined with different derivatives of chlorobenzoates in an isothermal titration calorimeter (ITC) allows a direct evaluation of the spontaneity of the threading of the aromatic anions into the micellar palisade. The comparison between the enthalpimetric curves with the ones for viscosity of the solutions, hydrodynamic radii of the aggregates (dynamic light scattering experiments), and the fraction of aromatic anions incorporated (diffusion-ordered spectroscopy experiments) allows the establishment of the variations of enthalpy with formation, growth, and decrease of the wormlike micelles (WLMs). The formation of WLMs with C14TAB is very favored (very exothermic) for titrations of chlorobenzoate derivatives which present the chlorine atom in positions 3 or 4 of the aromatic ring. However, the aggregation is highly unfavorable if chlorine is at position 2 of chlorobenzoate. According to the results, the high potential of the ITC to determine critical concentrations and the energies associated with the aggregation of a cationic surfactant and aromatic anions for the formation of WLMs was demonstrated.

Effect of the Hydrophobic Tail of a Chiral Surfactant on the Chirality of Aggregates and on the Formation of Wormlike Micelles.

The micellization of chiral enantiopure surfactants, dodecyl- N, N-dimethyl- N-( S)-(1-phenyl)ethylammonium bromide and hexadecyl- N, N-dimethyl- N-( S)-(1-phenyl)ethylammonium bromide, was investigated by circular dichroism spectroscopy and isothermal titration calorimetry. The formation of wormlike micelles (WLMs) upon the addition of sodium salicylate to the aqueous solutions of the surfactant was observed only in the case of hexadecyl- N, N-dimethyl- N-( S)-(1-phenyl)ethylammonium bromide. The presence of WLMs was assessed by cryogenic transmission electron microscopy, rheology, and isothermal titration calorimetry experiments, and their supramolecular chirality was investigated by circular dichroism spectroscopy. Depending on the length of the hydrophobic tail, molecular chirality is transferred into a different chiral supramolecular trait. Our findings demonstrate that hydrophobic interactions by controlling the organization and functions of self-assemblies also control the transcription of the chiral information from molecules to complex supramolecular systems.

Generation of a Chiral Giant Micelle.

Over the past few years, chiral supramolecular assemblies have been successfully used for recognition, sensing and enantioselective transformations. Several approaches are available to control chirality of discrete assemblies (e.g., cages and capsules), but few are efficient in assuring chirality for micellar aggregates. Optically active amino acid-derived surfactants are commonly used to generate chiral spherical micelles. To circumvent this limitation, we benefited from the uniaxial growth of spherical micelles into long cylindrical micelles usually called wormlike or giant micelles, upon the addition of cosolutes. This paper describes the unprecedented formation of chiral giant micelles in aqueous solutions of cetyltrimethylammonium bromide (CTAB) upon increasing addition of enantiopure sodium salt of 1,1'-bi-2-naphthol (Na-binaphtholate) as a cosolute. Depending on the concentrations of CTAB and Na-binaphtholate, chiral gel-like systems are obtained. The transition from spherical to giant micellar structures was probed using rheology, cryo-transmission electron microscopy, polarimetry, and electronic circular dichroism (CD). CD can be effectively used to monitor the incorporation of Na-binaphtholate into the micelle palisade as well as to determine its transition to giant micellar structures. Our approach expands the scope for chirality induction in micellar aggregates bringing the possibility to generate "smart" chiral systems and an alternative asymmetric chiral environment to perform enantioselective transformations.

Calorimetric and Light Scattering Investigations of the Transition from Spherical to Wormlike Micelles of C14TAB Triggered by Salicylate.

Although wormlike micelles (WLM) were first described more than 30 years ago, many aspects of their formation process are still unclear. Herein, a systematic experimental investigation of the process for wormlike micelle (WLM) formation in mixtures of tetradecyltrimethylammonium bromide (C14TAB) and salicylate (2-hydroxybenzoate) was carried out. This system was used as a model to investigate the conditions for the formation of the giant aggregate. For comparison, the other two isomers of salicylate (3- and 4-hydroxybenzoate) were also investigated, once in these cases wormlike micelles are not formed. The studies were based on calorimetric titration, static light scattering, and rheological measurements. Enthalpy changes upon titration of C14TAB into 2-hydroxybenzoate solutions revealed a highly cooperative and exothermic process that was associated with micelle growth. The size of the aggregates, obtained by static light scattering measurements, confirms the shape transition. In addition, the correlation of these two sets of results with measurements of micelle charge surface indicates that this transition occurs around the point of charge neutralization.

The elasticity of soap bubbles containing wormlike micelles.

Slow-motion imaging of the rupture of soap bubbles generally shows the edges of liquid films retracting at a constant speed (known as the Taylor-Culick velocity). Here we investigate soap bubbles formed from simple solutions of a cationic surfactant (cetyltrimethylammonium bromide - CTAB) and sodium salicylate. The interaction of salicylate ions with CTAB leads to the formation of wormlike micelles (WLM), which yield a viscoelastic behavior to the liquid film of the bubble. We demonstrate that these elastic bubbles collapse at a velocity up to 30 times higher than the Taylor-Culick limit, which has never been surpassed. This is because during the bubble inflation, the entangled WLM chains stretch, storing elastic energy. This extra energy is then released during the rupture of the bubble, yielding an additional driving force for film retraction (besides surface tension). This new mechanism for the bursting of elastic bubbles may have important implications to the breakup of viscoelastic sprays in industrial applications.

Molecular variations in aromatic cosolutes: critical role in the rheology of cationic wormlike micelles.

Wormlike micelles formed by the addition to cetyltrimethylammonium bromide (CTAB) of a range of aromatic cosolutes with small molecular variations in their structure were systematically studied. Phenol and derivatives of benzoate and cinnamate were used, and the resulting mixtures were studied by oscillatory, steady-shear rheology, and the microstructure was probed by small-angle neutron scattering. The lengthening of the micelles and their entanglement result in remarkable viscoelastic properties, making rheology a useful tool to assess the effect of structural variations of the cosolutes on wormlike micelle formation. For a fixed concentration of CTAB and cosolute (200 mmol L(-1)), the relaxation time decreases in the following order: phenol > cinnamate> o-hydroxycinnamate > salicylate > o-methoxycinnamate > benzoate > o-methoxybenzoate. The variations in viscoelastic response are rationalized by using Mulliken population analysis to map out the electronic density of the cosolutes and quantify the barrier to rotation of specific groups on the aromatics. We find that the ability of the group attached to the aromatic ring to rotate is crucial in determining the packing of the cosolute at the micellar interface and thus critically impacts the micellar growth and, in turn, the rheological response. These results enable us for the first time to propose design rules for the self-assembly of the surfactants and cosolutes resulting in the formation of wormlike micelles with the cationic surfactant CTAB.

Urea as hydrogelator of surfactants.

HYPOTHESIS: The formation of adducts via urea interaction with distinct classes of surfactants (cationic, anionic, nonionic, and zwitterionic), leading to their assembly into lamellar structures and subsequent formation of hydrogels. The characteristics of these hydrogels are associated with both, the length of the alkyl chain, and the specific head group of the surfactant molecules. EXPERIMENTS: Characterization of adduct formation was conducted using Wide-Angle X-ray Scattering (WAXS), while Small-Angle X-ray Scattering (SAXS) was employed to probe the subsequent assembly into lamellar structures. The kinetics of hydrogel formation were assessed through rheological measurements and observed thermal transitions utilizing Differential Scanning Calorimetry (DSC). FINDINGS: The investigation revealed a universal propensity for hydrogel formation across all surfactant classes. The formation arises from the interactions between urea molecules via hydrogen bonding, forming adducts around the surfactant chains. In sequence, the adducts self-assemble in lamellae. This process constructs the intricate three-dimensional network characteristic of the hydrogel. Furthermore, the kinetics of hydrogel formation, and their rheological properties under equilibrated conditions, were found to be significantly influenced by the nature of the polar head group of the surfactant molecules. This is the first evidence on the formation of adducts of urea with classes of surfactants. As they are common components in cosmetic, supramolecular hydrogels have high potential to be used in formulations.

Laboratory validation of the automated diagnosis of intestinal parasites via fecal sample processing for the recovery of intestinal parasites through the dissolved air flotation technique.

BACKGROUND: Techniques for diagnosing intestinal parasites need technological advancements in the preanalytical (collection/processing) and analytical (detection) stages. The dissolved air flotation (DAF) technique effectively recovers parasites from processed feces for routine diagnosis. Artificial intelligence (AI) is a practical and affordable alternative to modernize the analysis stage of microscopy images and generates high efficiency in the parasitological examination of feces. METHODS: The objective of this study was to standardize a laboratory protocol for stool processing using the DAF technique in conjunction with an automated diagnosis of intestinal parasites (DAPI) system. A total of 400 samples were obtained to perform the tests with the use of DAF to verify the recovery of the parasites as a function of the chemical reagent (polymer and surfactant), the volume of the flotation tube, and standardization of smear assembly on a microscopy slide, with automated analysis by DAPI. The DAF protocol that obtained the most satisfactory results in terms of parasite recovery (P < 0.05) and slide positivity was compared with the Three Fecal Test (TF-Test) protocol with manual (microscopists) and automated (DAPI) evaluation. We compared the sensitivity with the modified TF-Test technical protocol and the diagnostic agreement with the gold standard (Kappa) result. RESULTS: There was no significant difference in the parasite recovery between the 10 ml and 50 ml tubes (P > 0.05). The surfactants showed a range of parasite recoveries between 41.9% and 91.2% in the float supernatant. We obtained a maximum positivity of 73% of the assembled slides when we applied DAF processing with 7% CTAB surfactant and 57% positivity with the modified TF-Test technique. Regarding diagnostic performance, the TF-Test-modified and DAF techniques used in fecal processing for subsequent computerized analysis by AI presented sensitivities of 86% and 94%, with kappa agreements of 0.62 and 0.80 (substantial), respectively. CONCLUSIONS: The DAF protocol defined in this study and the DAPI system are innovative processes for parasite recovery and fecal debris elimination that are favorable for effectively detecting pathogenic structures in laboratory diagnosis.

Before and beyond the micellization of n-alkyl glycosides. A water-1H NMR relaxation study.

The interactions between the headgroups of n-alkyl glycoside (AG) and water molecules were studied by nuclear magnetic transverse relaxation times (T2) of the water protons before and beyond the micellization. Despite the low concentration of the surfactants (mM), their micellization induce strong effect on the T2 values of bulk water when the AG molecules self-aggregate into micelles. This is associated with the decreasing of the fraction of OH headgroups of AG to exchange protons with water molecules due to the OH headgroups intermolecular interactions of AG at the micelle surface. These findings support the computational results described in the literature, which indicate that the water hydrogen bonding to OH headgroups is perturbed at AG micelle surfaces.

More on polypseudorotaxanes formed between poly(ethylene glycol) and α-cyclodextrin.

A new interpretation for the mechanism associated with the spontaneous threading of α-CD, onto a PEG chain followed by the supramolecular hydrogel formation, is described. Beyond a specific stoichiometry, the complexation of α-CD and PEG results in the formation of a two-phase system. Besides the phase separation, for PEG with a molecular weight higher than 6000 Da, part of the polymer chains are unthreaded by the α-CD, leading to the formation of a supramolecular hydrogel. The kinetics for the complexation and the determination of the yield for equilibrated systems consisting of PEG (linear and star) are used to investigate the number of α-CD threaded before and after the phase separation. The results are compared with the prediction obtained from the application of the Poisson distribution and reveal the ratio between α-CD and PEG in each step of the process. Additionally, the kinetics for the hydrogel formation and its inner structure are investigated by using the proton NMR spin-spin relaxation of water.

Probing water mobility in confining channels of reverse wormlike micelles.

Reverse wormlike micelles are a potential template for chemical reactions in confined environments. Here, we use time-domain NMR to demonstrate the solvent effect on the mobility of water molecules. The higher the cohesive energy of alkanes, the lower the water mobility, and the less viscous the solution.

Increasing the aqueous solubility of the anesthetic propofol through wormlike micelle formation.

Propofol, a phenol derivative, is commonly employed as an intravenous anesthetic during clinical procedures, formulated as an oil/water emulsion due to its poor solubility in water. The stability limitations associated with emulsions have prompted research efforts towards developing aqueous formulations of propofol. In this work, we investigate the solubility enhancement of propofol in anionic and cationic surfactants. Our findings reveal that the solubility of propofol can increase significantly, up to 100-fold, depending on the nature of the micellar aggregate, as observed for alkylammonium halogenates CnTAB (for n = 12, 14 and 16), contrasting with the lower solubility with SDS. Interestingly, C14TAB and C16TAB demonstrate significantly higher solubility than C12TAB. This was attributed to the formation of wormlike micelles, in which the propofol molecules are positioned between the cationic heads of the surfactant molecules, changing the micellar curvature and the morphology of the aggregate. Therefore, the aromatic molecules in the micellar environment can be partitioned into the micellar cores and their palisades. Regarding C12TAB, the alkyl chain is too short to form wormlike micelles, thus, concentrating propofol molecules mainly into the micellar core, and consequently, leading to their aggregation. Solubility diagrams of propofol were constructed in conjunction with different surfactants. The systems exhibiting viscoelastic behavior, indicative of wormlike micelle formation, were further investigated using rheology. Additionally, the fluorescent properties of propofol enabled the examination of the anesthetic molecule within diverse micellar environments.

The effect of the molecular structure of hydroxypropyl methylcellulose on the states of water, wettability, and swelling properties of cryogels prepared with and without CaO2.

Hydroxypropyl methylcellulose (HPMC) belongs to the cellulose ether family that has hydroxyl groups substituted by hydrophobic methyl groups (DS) and hydrophilic hydroxypropyl groups (MS). Herein, the interactions between water molecules and cryogels prepared with HPMC in the presence and absence of a linear nonionic surfactant, as well as CaO2 microparticles, which react with water producing O2, were systematically investigated by sorption experiments and Time-Domain Nuclear Magnetic Resonance. Regardless of the DS and MS, most water molecules presented transverse relaxation time t2 typical of intermediate water and a small population of more tightly bound water. HPMC cryogels with the highest DS of 1.9 presented the slowest swelling rate of 0.519 ± 0.053 gwater/(g.s) and the highest contact angle values 85.250o ± 0.004o, providing the best conditions for a slow reaction between CaO2 and water. The presence of surfactant favored hydrophobic interactions that allowed the polar head of the surfactant to be exposed to the medium, resulting in a higher swelling rate and lower contact angle values. The HPMC with the highest MS presented the fastest swelling rate and the lowest contact angle. These findings are relevant for the formulations and reactions, where tuning the swelling kinetics is crucial for the final application.

Effects of hypertonic solutions on two species of human intestinal parasites during fecal examination.

Aim: Ova and parasite examination by flotation requires hypertonic solutions, which can damage the egg and cyst membranes, leading to false negatives. The authors investigated the harmful effects of ZnSO4 and C12H22O11 solutions on the ova and parasite examination. Materials & methods: The authors processed samples using the Three Fecal Test technique. Aliquots were floated in different pH levels, temperatures and solution densities. Results: Densities above 1.12 g/ml led structures to collapse after 6-10 min. pH neutralization of the ZnSO4 solution did not prevent the parasites from changing. Conclusion: All structures were altered when standard methods were performed. To delay collapse, the parasite floating under 5 °C is highly desirable.

Fecal exams require solutions that can damage the intestinal parasite's shape. This is bad for diagnosis. The authors investigated the harmful effects of these solutions on fecal exams. The authors processed samples using a technique called the Three Fecal Test. Fecal samples were floated in different conditions, including neutral and acidic solutions, high and low temperatures and varying densities of chemical solutions. Densities above 1.12 g/ml altered the structures of parasites. Neutral solutions did not prevent the structures from changing. The structures of all parasites were altered when the usual techniques were performed. Thus, the techniques for diagnosing intestinal parasites in feces must be improved. Temperatures under 5 °C are the best for preventing the destruction of parasite membranes.

Supramolecular Arrangement of Doxycycline with Sulfobutylether-ß-Cyclodextrin: Impact on Nanostructuration with Chitosan, Drug Degradation and Antimicrobial Potency.

Doxycycline (DX) is a well-established and broad-spectrum antimicrobial drug. However, DX has drawbacks, such as physicochemical instability in aqueous media and bacterial resistance. The inclusion of drugs in cyclodextrin complexes and their loading into nanocarriers can overcome these limitations. Thus, we studied the DX/sulfobutylether-ß-CD (SBE-ß-CD) inclusion complex for the first time and used it to reticulate chitosan. The resulting particles were evaluated by their physicochemical characteristics and antibacterial activity. DX/SBE-ß-CD complexes were characterized by nuclear magnetic resonance, infrared spectroscopy, thermal analysis, X-ray diffraction, and scanning electron microscopy (SEM), whereas DX-loaded nanoparticles were characterized by dynamic light scattering, SEM, and drug content. The partial inclusion of the DX molecule in CD happened in a 1:1 proportion and brought increased stability to solid DX upon thermal degradation. Chitosan-complex nanoparticles measured approximately 200 nm, with a narrow polydispersity and particles with sufficient drug encapsulation for microbiological studies. Both formulations preserved the antimicrobial activity of DX against Staphylococcus aureus, whereas DX/SBE-ß-CD inclusion complexes were also active against Klebsiella pneumoniae, indicating the potential use of these formulations as drug delivery systems to treat local infections.

Tuning the viscoelastic properties of bis(urea)-based supramolecular polymer solutions by adding cosolutes.

Polymers formed by the self-assembly of a bis(urea)-based polymer, 2,4-bis(2-ethylhexylureido)toluene (EHUT), in organic solvents such as octane are promising systems with remarkable rheological properties. This is the first self-assembled polymer recently reported as a hydrodynamic drag reducer for hydrocarbons. The rheology of diluted and semidiluted EHUT solutions can be tuned by specific interactions between the chains, modulated by the nature of the solvent and the presence of additives. In this article, rheological, thermal and SANS measurements were performed in order to investigate the competition between EHUT self-assembly and its interaction with specific molecules (benzene, benzyl alcohol, and ethanol) that can interact with EHUT unimers via hydrogen bonds and π-π interactions. No substantial rheological, thermal, or structural effect is observed when benzene is added to the systems. However, ethanol and benzyl alcohol interact with EHUT unimers through hydrogen bonds, drastically decreasing the viscoelasticity of the solutions. In addition, benzyl alcohol can interact with EHUT polymers by π-stacking interactions, playing an important role in tuning the rheological properties of the systems.