Rigid Film Research Articles

Foaming, emulsifying and rheological properties of extracts from a co-product of the Quorn fermentation process

This study assessed the functional profile (foaming, emulsifying and rheological properties), proteomic and metabolomic composition of a naturally foaming and currently unexploited co-product (centrate) from the Quorn fermentation process. Due to the low environmental footprint of this process the centrate is a potential source of sustainable functional ingredients for the food industry. A range of fractions were isolated from the centrate via successive ultrafiltration steps. The retentate 100 (R100) fraction, which was obtained following a 100 kDa ultrafiltration, displayed good foaming, emulsifying and rheological properties. R100 solutions and oil-in-water emulsions displayed high viscosity, while R100 solutions and hydrogels showed high viscoelasticity. R100 foams displayed high stability while oil-in-water R100 emulsions showed small and stable oil droplet size distributions. Large mycelial aggregates were reported in R100 solutions and gels, correlating with their high viscosity and viscoelasticity. A dense mycelial network was observed in R100 foams and contributing to their stability. In parallel tensiometry measurements highlighted the presence of interfacially active molecules in R100 which formed a rigid film stabilising the oil/water interface. A number of functional metabolites and proteins were identified in the centrate, including a cerato-platanin protein, cell membrane constituents (phospholipids, sterols, glycosphingolipids, sphingomyelins), cell wall constituents (chitin, chitosan, proteins), guanine and guanine-based nucleosides and nucleotides. This study highlighted the potential of functional extracts from the Quorn fermentation process as novel ingredients for the preparation of sustainable food products and the complex and specific nature of the centrate’s functional profile, with contributions reported for both mycelial structures and interfacially active molecules.Graphical abstract

Interfacial properties pertinent to W/O and O/W emulsion systems prepared using polyaromatic compounds

Establishing interfacial science to understand molecular mechanisms of stabilizing water in heavy crude oil (W/O) emulsions is challenging due to non-transparent nature of crude oil even in diluted systems, as most of the interfacial property measurements are based on visualization of the experimental systems. This study investigates whether interfacial properties measured using transparent O/W emulsion systems could be used to understand the stability of W/O emulsion systems. With the same chemistry of interfacially active polyaromatic compounds (C5Pe and C5PeC11) in xylene as the model oil, the interfacial tension, crumpling ratio, dilatational rheology and coalescence time of W/O and O/W systems were measured. For less surface active C5PeC11, the interfacial tensions for W/O and O/W systems were similar. For more surface active C5Pe, the interfacial tension of the W/O system was lower than that of the O/W system, while the film rigidity and viscoelasticity of the W/O system were higher than that of the O/W system. At low C5Pe concentration, the coalescence time for the W/O system was lower than that for the O/W system with the coalescence time for the W/O system being higher at higher C5Pe concentrations. The results reveal that even though the interfacial properties measured using reverse O/W system exhibit similar qualitative trends, care should be taken when quantitatively studying W/O emulsions using interfacial property measurements of the O/W system due to the difference in most of the interfacial properties measured using the W/O and O/W systems.

Molecular Destabilization Mechanism of Asphaltene Model Compound C5Pe Interfacial Film by EO-PO Copolymer: Experiments and MD Simulation

It is commonly believed that asphaltenes are the main components that contribute to the formation of the rigid film which stabilizes W/O emulsions in petroleum industry. In order to investigate the...

Self-assembly of polyhedral oligomeric silsesquioxane structures through ion exchange

In this study, we synthesized 3-chloroammoniumpropyl polyhedral oligomeric silsesquioxanes (CAP-POSS) by acid hydrolysis and condensation. Partial ion exchange resulted in the formation of supramolecular structures through electrostatic interactions. The interactions between POSS macroions were led by multiple hydrogen bonds that form supramolecular structures. After ion exchange, the structures of the CAP-POSS reduce the symmetry by the exchange of counterions and associate to form rigid transparent films at room temperature. The amount of chloride modulated the size and structure of macroions aggregates in the supramolecular films. Regardless of the amount of chloride removed, the films were formed of mass-fractal like structures with sizes ranging from 80 to 28 nm. The surface energy was proportional to the free amine content, and UV–vis was a light transmission characteristic. Therefore, the use of partial ion exchange represents an alternative to design of supramolecular POSS structures with properties tunable through multiple hydrogen bonds.

Biohybrid Actuators Based on Skeletal Muscle-Powered Microgrooved Ultrathin Films Consisting of Poly(styrene-block-butadiene-block-styrene)

This paper describes a biohybrid actuator consisting of a microgrooved thin film, powered by contractile, aligned skeletal muscle cells. The system was made of a thermoplastic elastomer [SBS, poly(styrene-block-butadiene-block-styrene)]. We prepared SBS thin films with different thicknesses (0.5-11.7 μm) and Young's moduli (46.7-68.6 MPa) to vary their flexural rigidity. The microgrooves on the SBS thin film resembled the microstructure of the extracellular matrix of muscle and facilitated the alignment and differentiation of skeletal muscle cells. Electrical stimulation was applied to self-standing biohybrid thin films to trigger their contraction, enabled by the low flexural rigidity of the SBS thin film. Finite element model simulations were also examined to predict their contractile behavior. We achieved the prediction of displacements, which were rather close to the actual values of the SBS thin film: the discrepancy was <5% on the X axis. These results pave the way for in silico prediction of the contractile capabilities of elastomeric thin films. This study highlights the potential of microgrooved SBS thin films as ultraflexible platforms for biohybrid machines.

Biosurfactant-modified palygorskite clay as solid-stabilizers for effective oil spill dispersion

An effective and conventional remediation technique in marine oil spills is to apply chemical dispersants to emulsify oil slicks into small oil droplets. Still, the potential hazards of chemical dispersants onto the marine ecosystem have motivated the research for environmentally friendly alternative while keeping exceptional dispersion ability. Here, we showed that the mixture of palygorskite (PAL) and rhamnolipid (Rha) formed a biocompatible alternative to synthetic surfactants used for oil spill dispersion. The oil droplets dispersed by R-PAL presented a small average size and long-term stability, which illustrated the synergistic interactions between Rha and PAL acting as an efficient dispersant in artificial sea water (ASW). Due to the strong flocculation caused by high salinity, PAL alone was not effective emulsifiers in ASW. A small amount of Rha could played a major role in modifying the surface characteristics of PAL and decreasing oil-water interfacial tension. Therefore, PAL particles irreversibly adsorbed onto the oil-ASW interface and formed a rigid interfacial film around oil droplets in the presence of Rha, which offered an efficient barrier to droplet coalescence. The synergistic interactions between PAL and Rha could enable the dispersion of tetradecane in ASW. Such a functionality was further tested in dispersing crude oil in ASW. The study presents a new strategy of using a mixture of PAL and Rha for oil dispersion, thus providing an ecofriendly alternative to conventional dispersants.

Self-assembly of reactive difunctional molecules on nickel electrode

Self-assembly of some reactive difunctional molecules such as mercaptopyridine, pyrazine, phenylene diisocyanide, amino ethanethiol and simple hexadecane thiol molecule have been formed on nickel surface. The adsorption behaviour has been monitored by Quartz crystal microbalance with energy dissipation (QCM-D) and the results show that these molecules form thin rigid films on the surface. QCM-D results also reveal that nickel atoms on the surface are highly stable and do not undergo any corrosion or removal of nickel atoms from the surface during the adsorption process as observed with gold surface for these molecules. Reflection-absorption infrared spectral (RAIR) measurements were performed to study the mode of binding, order and packing of these molecules on nickel surface. Ellipsometric thickness results are comparable to theoretical values and water contact angle measurements were carried out to study the change in the wettability and the observed values are slightly lesser than the data reported in literature for these molecules on gold surface. The charge transfer kinetics of these modified nickel surface have been studied by cyclic voltametry using a ferrocene redox probe in solution. An increase in the peak potential separation of the redox species was observed with the modified surfaces compared to bare nickel which may be due to the insulating nature of these monolayers.

Investigation of non-adhesive behaviour of waterborne polyurethane dispersions

The current work probe the thermo-mechanical defects responsible for the non-adhesive behaviour of waterborne polyurethane dispersions (PUDs). A sequence of composition of PUDs has been developed by using blended macrodiols of hydroxyl terminated polybutadiene (HTPB) and polypropylene glycol (PPG). The urethane linkages have been developed by the use of 1,6 hexane diisocyanate (HDI). The polymer contents synthesized by prepolymer method have been dispersed in deionized water to develop ecofriendly dispersions. The dispersions were subjected to probe tack analysis to determine the extent of adhesiveness. The adhesive properties evaluated from probe tack curve show tack adhesion energy from 10.5 to 42. 5 J-m-2. The DMA analysis revealed high storage modulus up to 1.42 MPa for PUD films. The adhesive properties evaluated by the consideration, of the ratio of loss tangent, to the storage modulus (tanδ / E′) for comparison resulted in the values from 0.15 -0.71 MPa-1. The Tg ranges from 65 °C to 57 °C. The composition of blended macrodiols of high molecular weight HTPB results in tack less rigid films of PUDs.

Saliva-coated titanium biosensor detects specific bacterial adhesion and bactericide caused mass loading upon cell death

Bacteria adhering to implanted medical devices can cause invasive microbial infections, of e.g. skin, lung or blood. In dentistry, Streptococcus gordonii is an early oral colonizer initiating dental biofilm formation and also being involved in life-threatening infective endocarditis. To treat oral biofilms, antibacterial mouth rinses are commonly used. Such initial biomaterial-bacteria interactions and the influence of antibacterial treatments are poorly understood and investigated here in situ by quartz crystal microbalance with dissipation monitoring (QCM-D). A saliva-coated titanium (Ti) biosensor is applied to analyze possible specific signal patterns indicating microbial binding mechanisms and bactericide-caused changes in bacterial film rigidity or cell leakage caused by a clinically relevant antibacterial agent (ABA), i.e., a mouth rinse comprising chlorhexidine (CHX) and cetylpyridinium chloride (CPC). Apparent missing mass effects during the formation of microscopically proven dense and vital bacterial films indicate punctual, specific binding of S. gordonii to the saliva-coated biosensor, compared to unspecific adhesion to pure Ti. Coincidentally to ABA-induced killing of surface-adhered bacteria, an increase of adsorbed dissipative mass can be sensed, contrary to the prior mass-loss. This suggests the acoustic sensing of the leakage of cellular content caused by bacterial cell wall rupturing and membrane damage upon the bactericidal attack. The results have significant implications for testing bacterial adhesion mechanisms and cellular integrity during interaction with antibacterial agents.

Development and characterization of biodegradable films based on Pereskia aculeata Miller mucilage

Ora-pro-nobis mucilage (MOPN) is a polysaccharide extracted from the leaves of Pereskia aculeata Miller (Cactaceae family), and is composed of the biopolymer arabinogalactan. The aim of this study was to evaluate the viability of MOPN-based films supplemented with glycerol. The films were developed using the casting technique in five treatments: 1.5% MOPN with 20% glycerol (w/w), 1.5% MOPN with 25% glycerol, 1.8% MOPN with 22.5% glycerol, 2.0% MOPN with 20% glycerol, and 2.0% MOPN with 25% glycerol. The films were characterized according to their rheological, optical, mechanical, thermal, and water vapor permeability (WVP) properties. The film-forming solution presented shear thinning and elastic behavior (G'>G"). Films with 1.5% MOPN and 20% glycerol presented greater elongation (46.10%), higher puncture strength 13.8 N, and lower WVP (8.288 g water·mm·day−1·m-²·kPa−1) than the other evaluated films. Glycerol acted as a cross-linking agent, increasing the bond between the MOPN chains, generating more rigid films. These films presented two glass transition temperatures, below 0 °C and around 60 °C. Thermogravimetry indicated that MOPN contributes to better thermal stability of the films. MOPN is a promising alternative for the use of biodegradable and/or edible packagings, and the best formulation studied was 1.5% MOPN and 20% glycerol.

Fracture Mechanics and Oxygen Gas Barrier Properties of Al₂O₃/ZnO Nanolaminates on PET Deposited by Atomic Layer Deposition.

Rapid progress in the performance of organic devices has increased the demand for advances in the technology of thin-film permeation barriers and understanding the failure mechanisms of these material systems. Herein, we report the extensive study of mechanical and gas barrier properties of Al2O3/ZnO nanolaminate films prepared on organic substrates by atomic layer deposition (ALD). Nanolaminates of Al2O3/ZnO and single compound films of around 250 nm thickness were deposited on polyethylene terephthalate (PET) foils by ALD at 90 °C using trimethylaluminium (TMA) and diethylzinc (DEZ) as precursors and H2O as the co-reactant. STEM analysis of the nanolaminate structure revealed that steady-state film growth on PET is achieved after about 60 ALD cycles. Uniaxial tensile strain experiments revealed superior fracture and adhesive properties of single ZnO films versus the single Al2O3 film, as well as versus their nanolaminates. The superior mechanical performance of ZnO was linked to the absence of a roughly 500 to 900 nm thick sub-surface growth observed for single Al2O3 films as well as for the nanolaminates starting with an Al2O3 initial layer on PET. In contrast, the gas permeability of the nanolaminate coatings on PET was measured to be 9.4 × 10−3 O2 cm3 m−2 day−1. This is an order of magnitude less than their constituting single oxides, which opens prospects for their applications as gas barrier layers for organic electronics and food and drug packaging industries. Direct interdependency between the gas barrier and the mechanical properties was not established enabling independent tailoring of these properties for mechanically rigid and impermeable thin film coatings.

Friction and Adsorption Properties of Oleic Acid-Based Gemini Amphiphile at Silica/Ester Oil Interfaces.

We characterized the friction and adsorption properties of an oleic acid-based gemini amphiphile having two carboxylic acid headgroups. We employed silica as a solid material, and diethyl sebacate and bis (2-ethylhexyl) sebacate as polar ester oils. Oleic acid and stearic acid were used as comparative amphiphilic materials. These amphiphiles were soluble in the ester oils, and the solubility of the gemini amphiphile was lower than that of the other two amphiphiles. Quartz crystal microbalance with dissipation monitoring measurements suggested that the gemini amphiphile had greater adsorption capability than the two comparative amphiphiles. The greater adsorption density of the gemini amphiphile resulted in the formation of a rigid interfacial film, as suggested by the normal force curves obtained by atomic force microscopy (AFM). We assessed the friction property of these systems using a ball-on-plate-type friction analyzer and by friction-mode AFM (friction force curve). These measurements confirmed that the gemini amphiphile had a smaller kinetic friction coefficient than that of the other two amphiphiles. These results suggest the potential of the gemini amphiphile as a friction modifier in polar oils.

Emulsions stabilized with mixed SiO2 and Fe3O4 nanoparticles: mechanisms of stabilization and long-term stability.

The stabilization of oil-in-water emulsions with SiO2 and Fe3O4 nanoparticles was investigated. The mechanism of emulsion stabilization was altered by changing the mass ratio of negatively charged Ludox HS-30 to positively charged Ludox CL nanoparticles in emulsions. At a mass ratio of nanoparticles between 0.3 : 1.0 and 1 : 1, small nanoparticle heteroaggregates adsorbed on the surface of the oil droplets, giving them resistance to coalescence. The interface film rigidity was enough to prevent droplet deformation. After creaming, the oil-phase fraction in the residual emulsion increased up to dense packing, but did not exceed 0.74-0.78 for a long time. At the mass ratio of (1.5-2.5) : 1.0, the emulsions were kinetically stable to creaming and coalescence due to the formation of a three-dimensional network of nanoparticle heteroaggregates in the aqueous phase. At a mass ratio of Ludox HS-30 to Ludox CL nanoparticles above 3 : 1, large heteroaggregates were formed in the aqueous phase and the rapid separation of the oil and water phases from the emulsions occurred. Such a change in the stability of emulsions was due to a significant alteration of the value of the net ζ-potential of the heteroaggregates. In the case of stabilization with Ludox CL and Fe3O4 nanoparticles, emulsions with nanoparticle networks in the aqueous phase were obtained at pH 8, and these emulsions were stable against creaming and coalescence. Emulsions resistant to coalescence were produced in the systems with Ludox CL and Fe3O4 nanoparticles at pH 4-6 and in systems with Ludox HS-30 and Fe3O4 nanoparticles at pH 2-6.

Non-endocrine disruptor effect for cardanol based plasticizer

A series of bio-based epoxidized plasticizers (CExEp) for soft PVC was synthesized from cardanol and various fatty acids by esterification and epoxidation of the fatty and cardanol unsaturations. The plasticizing properties of these additives for PVC films were proved considering thermal and mechanical data. They seem to be a potential bio-based alternative plasticizer to diisononyl phthalate (DINP), one of the most widespread phthalate plasticizers, with less rigid and stable films. The synergy between epoxy groups, cardanol ring and fatty chains to elaborate efficient primary plasticizers was demonstrated. Moreover, the eco-toxicity using daphnies, algae, and plants as model organisms and endocrinal disruptor tests (YES/YAS) were realized. Our results revealed that the fatty cardanol plasticizer causes a global decrease in toxicity compared to DINP and no harm for environment and human health were detected without endocrine perturbation effect. These positive results of toxicology allow to consider these cardanol plasticizers in industrial applications as alternative to DINP.

Preparation and characterization of soy protein films reinforced with cellulose nanofibers obtained from soybean by-products

In this paper, we report the preparation of nanofibers obtained from low-cost agro-industrial by-products (soybean hulls and pods) and their use as nano reinforcers of soy protein films. From hulls, we obtained white and stable in-time aqueous dispersions of cellulose nanofibers of about 20 nm wide and 500 nm long and a hydrodynamic diameter of 269 nm, with a marked increase in the crystalline index as compared to raw material. Filmogenic solutions of soy proteins were prepared using glycerol as a plasticizer and different amounts of cellulose nanofibers (0; 10; 20 and 40% in relation to the amount of soy protein). The rheological behavior of filmogenic solutions containing nanofibers suggests an interaction between matrix and reinforcements. Films were prepared by casting of filmogenic solutions. As a result, we obtained films with a homogeneous surface having a large number of nanofibers, showing increasing opacity in samples with larger amounts of cellulose nanofibers. The addition of nanofibers decreases the film's susceptibility to water, by which a significant decrease in the total soluble matter and swelling in water was observed with an increase in contact angle. In addition, mechanical properties were also improved, obtaining more rigid films as the number of nanofibers increased.

Synthesis of Pt/M (M = Au, Rh) Nanoparticles in Microemulsions: Controlling the Metal Distribution in Pt/M Catalysts

The synthesis of Au/Pt and Pt/Rh nanoparticles in microemulsions by a one-pot method has been studied by computer simulation using stoichiometric and in-excess reducing agent. Our study demonstrates that Pt is reduced faster in the presence of Rh than in the presence of Au, and this acceleration is attributed to the higher availability of reducing agent in the Pt/Rh than in Au/Pt synthesis. Final bimetallic nanoparticles show a better metal segregation in Pt/Rh when compared with Au/Pt nanoparticles. In Au/Pt synthesis, Pt reaction rate depends on the ease with which reactants can be exchanged between micelles and the availability of reducing agent. When Pt/Rh nanoparticles are synthesized using a rigid film, the slow intermicellar exchange runs together with the slow reduction rates of the metals. It results in a very slow consumption of reducing agent, so the amount of reducing agent does not affect Pt reaction rate.

An Experimental Investigation of Water Effects on Asphaltene Surface Behavior through Interfacial Tension Measurements

As a physiochemical property, asphaltenes are known to be one the most surface active compounds in crude oil. Due to such property, their behavior is most probably influenced by fluid-fluid interactions at the contact surface (interface). Potentially and naturally, in most cases, water is in contact with crude oil and is co-produced with it as well. Considering that asphaltene molecules are polar compounds similar to water molecules, asphaltenes are interfacially affected by water while they are absorbed to the interface. Such effects could be investigated by interfacial tension (IFT) changes when de-ionized water is used and dead-crude oil does not contain other surface active impurities like metallic compounds. In this study, extensive IFT experiments were conducted between three different oil samples and distilled water in a wide range of pressure from 2000 to 0 psia. The reversibility of asphaltene absorbance to the interface was also investigated by reversing the pressure path from 0 to 2000 psia. The results show that oil/water IFT changes with pressure, but upward/downward oscillations were detected. Such an oscillating behavior of IFT trends was related to asphaltenes surface activity as the oil samples used did not contain other impurities. Oscillations were reduced as resin to asphaltene ratio was increased, suggesting the non-absorbable behavior of the asphaltenes stabilized by resins. A microscopic surface experiment on one of the samples showed that at a certain concentration and particle size, a rigid film of absorbed asphaltenes was created at the interface instantaneously. The high rigidity of such a film gives rise to a hypothesis, which states that water affects asphaltene surface behavior possibly through strong hydrogen bonding (H-bond). Reversing the pressure path revealed that asphaltene surface absorbance is partially irreversible. The experiments were conducted three times, and each data set was presented along with an average of three sets for each sample.

Fluorescent Hydrogel‐Coated Paper/Textile as Flexible Chemosensor for Visual and Wearable Mercury(II) Detection

AbstractIn some industrial districts, abuse discharge of waste water has resulted in serious Hg2+ pollution in seafood, grain, and even drinking water. In order to protect people from mercury(II)‐polluted food and water, many solid‐state fluorescent Hg2+‐sensing materials are developed in terms of facile operation. However, one primary challenging issue is the restricted sensitivity caused by hindered slow diffusion of aqueous testing samples inside these conventional hydrophobic, dense, and rigid film materials. Herein, robust hydrophilic fluorescent hydrogel‐coated flexible paper/textile film chemosensors are reported. Their design relies on a specific chemical reaction between Hg2+ and the grafted thiourea moieties to induce remarkable “green‐to‐blue” emission color change. Thanks to their hierarchical porous structures fixed by interwoven paper/textile fibers, these flexible chemosensors allow fast capillary‐force‐driven mercury(II) diffusion into the hydrophilic hydrogel matrix, thus enabling visual detection of nearly nM‐level Hg2+. On this basis, robust fluorescent hydrogel‐coated wearable sensing gloves are fabricated for the first time, which significantly facilitate infield visual detection and effectively protect operators far from the toxic Hg2+‐polluted samples. These developed flexible wearable sensing systems might not only hold great potential applications in mercury(II) detection, but also inspire the development of next‐generation sensing apparatus for other food and environmental pollutants.

Influence of inter-domain dynamics and surrounding environment flexibility on the direct electrochemistry and electrocatalysis of self-sufficient cytochrome P450 3A4-BMR chimeras

The linker region of multi-domain enzymes has a very important role for the interconnection of different enzyme modules and for the efficiency of catalytic activity. This is particularly evident for artificial chimeric systems. We characterised an artificial self-sufficient enzyme developed by genetic fusion of the catalytic domain of cytochrome P450 3A4 and reductase domain of Bacillus megaterium BM3 (BMR).Here we report the direct electrochemistry of 3A4-BMR chimeras immobilised on glassy carbon electrodes and we investigated the effect of inter-domain loop length and immobilising environment flexibility on both redox properties and electrocatalysis. We observe that redox potential can be modulated by the linker length and the immobilising layer flexibility. In addition, enzyme inter-domain dynamics and environment flexibility also modulate 3A4-BMR turnover efficiency on electrode system. Vmax values are increased up to about 100% in the presence of testosterone and up to about 50% in presence of tamoxifen by decreasing immobilising film rigidity. The effect on 3A4-BMR Vmax values is dependent on inter-domain loop length with 3A4-5GLY-BMR chimera being the more affected. The underlying reason for these observations is the potential motion of the FMN domain that is the key to shuttle electrons from FAD to haem.

Prediction studies of environment-friendly biodegradable polymeric packaging based on PLA. Influence of specimens’ thickness on the hydrolytic degradation profile

Application of new biodegradable polymer packaging based on polylactide (PLA), susceptible to organic recycling, can help in the waste reduction in landfills. In this paper, the results of the study on abiotic degradation of PLA and its blend containing 15 mol% of poly[(R,S)-3-hydroxybutyrate], as a model for the first step of organic recycling were presented. The samples used for this study have different shapes and thicknesses: rigid films and cuboid-bars. Particular emphasis was placed on determining the pattern of degradation products released into the medium. Originally, the results of present study revealed that the application of electrospray ionization mass spectrometry supported by high performance liquid chromatography allowed envisaging the differences in the degradation products pattern released from the studied PLA-based samples differing in thickness. The significant differences in degradation products pattern were predominately observed in the first steps of incubation process and are caused by an autocatalytic effect, which occurs mainly during degradation of the large size PLA samples. Although, the thickness of PLA-based packaging changes the degradation product patterns, however this does not increase the total amounts of acids released to the medium. Thus, it may be concluded that thickness should not affect significantly organic recycling of the packaging.