Amphiphilic Films Research Articles

Harnessing microscopically opposite wettability in Janus nanofiber film for solar steam generation and photodegradation

Amphiphilic Janus nanofibers film composed of microscopically assembled hydrophilic and hydrophobic nanofibers is fabricated as a base film for the solar steam generator possessing functions of solar steam generation and photodegradation. The amphiphilic Janus nanofibers film integrates many advantageous properties including water pumping, thermal resisting, self floating, salt resisting, and high stability, which make it an excellent base film for solar steam generators. The mixture comprising carbon nanotubes, black TiO2 nanoparticles and poly(dopamine) is synthesized as a dual-functional photothermal layer on the solar steam generator for realizing photothermal conversion and photocatalysis. The fabricated solar steam generator can achieve a superior water evaporation rate (2.491 kg m−2 h−1, 1 sun) and synchronously degrade organic pollutants. Furthermore, it is delighted to find that the water evaporation rate can be boosted while treating organic-contaminated water. The synergistic property of solar steam generation and photodegradation offers an inspiration in the fields of wastewater elimination and clean water generation.

Anti-fogging properties of amphiphilic copolymer films deposited by chemical vapor deposition (CVD)

This study demonstrates the deposition of an amphiphilic copolymer as an anti-fogging coating on the glass and mirror surfaces. For this purpose, copolymer films of 2,2,2,3,4,4,4,4 hexafluorobutyl acrylate (HFBA) with 2-(dimethylamino)ethyl methacrylate (DMAEMA) were synthesized using initiated chemical vapor deposition (iCVD). During the iCVD process by adjusting the flow rate ratio of the monomers, the amount of fluorinated moiety in the P(HFBA-DMAEMA) was systematically tuned, which was confirmed through FTIR and XPS analyses. According to the water contact angle measurements, coatings were shown to be more hydrophobic with increasing fraction of fluorine atoms in their structures. The P(HFBA-DMAEMA)-deposited surfaces showed outstanding and long-lasting anti-fogging performance while maintaining high optical transmissivity. Films were observed to be functional in terms of anti-fogging behavior even after 1-year from the initial coating process, which confirms the durability of the films.

Investigating the anti-bioadhesion properties of short, medium chain length, and amphiphilic polyhydroxyalkanoate films

Silicone materials are widely used in fouling release coatings, but developing eco-friendly protection via biosourced coatings, such as polyhydroxyalcanoates (PHA) presents a major challenge. Anti-bioadhesion properties of medium chain length PHA and short chain length PHA films are studied and compared with a reference Polydimethylsiloxane coating. The results highlight the best capability of the soft and low-roughness PHA-mcl films to resist bacteria or diatoms adsorption as compared to neat PDMS and PHBHV coatings. These parameters are insufficient to explain all the results and other properties related to PHA crystallinity are discussed. Moreover, the addition of a low amount of PEG copolymers within the coatings, to create amphiphilic coatings, boosts their anti-adhesive properties. This work reveals the importance of the physical or chemical ambiguity of surfaces in their anti-adhesive effectiveness and highlights the potential of PHA-mcl film to resist the primary adhesion of microorganisms.

Preparation of amphiphilic polyquaternium nanofiber films with antibacterial activity via environmentally friendly microfluidic-blow-spinning for green food packaging applications

Green food packaging plays an important role in environmental protection and sustainable development. Therefore, it is advisable to employ low-energy consumption manufacturing techniques, select environmentally friendly materials, and focus on cost-effectiveness with high production yields during the production process. In this study, an amphiphilic polyquaternium called PBzCl was proposed and synthesized by free radical polymerization of cost-efficient quaternary ammonium salts and methacrylate monomers. Then, biodegradable PCL and PVP were used to rapidly prepare the PBzCl@PCL/PVP nanofiber films via environmentally friendly microfluidic-blow-spinning (MBS). The best antibacterial effect was observed at a PBzCl loading concentration of 13.5%, and the PBzCl@PCL/PVP nanofiber films had 91% and 100% antibacterial rates against Escherichia coli and Staphylococcus aureus, respectively. Besides, the loading of PBzCl improved the water stability of the PCL/PVP nanofiber films, and the films also showed excellent biocompatibility. Overall, PBzCl@PCL/PVP nanofibre films have promising food packaging potential.

Physiological function of hydrophobin Vmh3 in lignin degradation by white-rot fungus Pleurotus ostreatus.

Hydrophobins are small-secreted proteins comprising both hydrophobic and hydrophilic parts, that can self-assemble into an amphiphilic film at the air-liquid interface. More than 20 hydrophobin genes have been estimated in the white-rot fungus Pleurotus ostreatus. In our previous studies, three hydrophobin genes were shown to be predominantly expressed under ligninolytic conditions, and only vmh3 was downregulated in both the delignification-deficient mutant Δgat1 and Δhir1 strains. Here, we focused on the function of the hydrophobin Vmh3 to clarify its physiological role in lignin degradation. When the hyphae were observed by transmission electron microscopy, deletion of vmh3 resulted in the disappearance of black aggregates at the interface between the cell wall and outer environment. Deletion of vmh3 resulted in reduced hydrophobicity when 0.2% sodium dodecyl sulfate was dropped onto the mycelial surface. These results suggest that Vmh3 functions on the cell surface and plays a major role in mycelial hydrophobization. Furthermore, the Δvmh3 strain showed a marked delay in lignin degradation on beech wood sawdust medium, while the production of lignin-modifying enzymes was not reduced. This study demonstrated, for the first time, the possible effect of hydrophobin on lignin degradation by a white-rot fungus.

Oligo(2-alkyl-2-oxazoline)-based graft copolymers for marine antifouling coatings

Poly(ethylene glycol) (PEG)-based graft copolymers have been widely applied for the modification of poly(dimethyl siloxane) (PDMS)-based coatings that resist marine biofouling. In this research, we synthesized oligo(2-alkyl-2-oxazoline) (OAOXA)-based graft copolymer analogues, and subsequently tested their applicability in the formulation of structurally similar coatings, aiming to highlight the influence of polymer composition on biopassive properties. In particular, poly(dimethyl siloxane methacrylate)-co-oligo(2-alkyl-2-oxazoline)methacrylate copolymers were synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization, starting from oligo(2-ethyl-2-oxazoline)- and oligo(2-methyl-2-oxazoline)-methacrylate macromonomers (OEOXMA and OMOXMA, respectively). Amphiphilic copolymer films with OAOXA grafts were found to be more hydrophilic with respect to those obtained using PEG analogues. PDMS coatings containing the graft copolymers as surface additives were tested towards the settlement of the macrofouler Ficopomatus enigmaticus and the diatom Navicula salinicola. The biofouling experiments indicated that OAOXA-containing films showed a comparable and in some cases improved performance with respect to their PEG-based counterparts, thus highlighting how OAOXA-based graft copolymers represent a valid alternative to PEG derivatives as surface-active additives to design antibiofouling coatings.

Features of disruption mutants of genes encoding for hydrophobin Vmh2 and Vmh3 in mycelial formation and resistance to environmental stress in Pleurotus ostreatus.

Hydrophobins, which are small-secreted proteins with both hydrophobic and hydrophilic parts, can self-assemble into an amphiphilic film at the air-water interface, helping the fungus to form aerial hyphae. In the agaricomycete Pleurotus ostreatus, more than 20 putative hydrophobin genes have been predicted. Of these, two hydrophobin genes, vmh2 and vmh3, are predominantly expressed in the vegetative mycelium. In this study, we focused on the functions of Vmh2 and Vmh3 in vegetative mycelia. Based on the observation of the mycelial cross-section by transmission electron microscopy and the disappearance time of water droplets on the mycelial surface, Vmh2 and Vmh3 were considered essential for the maintenance of the surface hydrophobicity of the mycelium. The Δvmh3 and Δvmh2Δvmh3 strains exhibited relatively slower aerial mycelia formation on a liquid medium, and no significant alteration was observed in Δvmh2 strains. Only the Δvmh3 and Δvmh2Δvmh3 strains grew slower than the wild-type strain under stress conditions involving SDS and H2O2 on agar plates. This study revealed possible distinct roles for these hydrophobins in stress resistance. These results suggest that Agaricomycetes, including P. ostreatus, have evolved to possess multiple different hydrophobins as a means of adapting to various environments.

Amphiphilic Copolymer Thin Films with Short Fluoroalkyl Side Chains for Antibiofilm Properties at the Solid–Liquid–Air Interface

Amphiphilic Copolymer Thin Films with Short Fluoroalkyl Side Chains for Antibiofilm Properties at the Solid–Liquid–Air Interface

Self-Assembled Monolayer Coatings on Gold and Silica Surfaces for Antifouling Applications: A Review

The resistance of surfaces to biomaterial adsorption/adhesion is paramount for advancing marine and biomedical industries. A variety of approaches that involve bioinert materials have been developed to modify surfaces. Self-assembled monolayers (SAMs) are powerful platforms in which the surface composition is easily fabricated and a well-defined structure is provided; thus, the molecular-level interaction between biomolecules/biofoulants and the surface can be understood. In this review, we describe a wide variety of SAM structures on gold and silica surfaces for antifouling applications and the corresponding mechanism of nonfouling surfaces. Our analysis divides the surface properties of films into the following types: (1) hydrophilic, (2) hydrophobic, and (3) amphiphilic films.

Genipin-crosslinked amphiphilic chitosan films for the preservation of strawberry

As a material for films used to keep fruits fresh, chitosan has attracted extensive interest because of its advantages of degradability, environmental friendliness, and biocompatibility. In this study, two amphiphilic chitosan derivative films were prepared by crosslinking N-2-hydroxypropyl-3-butyl ether-O-carboxymethyl chitosan (HBCC) and N-2-hydroxypropyl-3-(2-ethylhexyl glycidyl ether)-O-carboxymethyl chitosan (H2ECC)) with genipin, an excellent natural cross-linking agent. The microstructures, mechanical properties, water vapor permeability, swelling ratios, light transmittance, wettability, thermal stability, antibacterial properties, and biocompatibility of the crosslinked films were characterized. The results showed that the crosslinked films had compact structures, low moisture permeability, strong water resistance, strong ultraviolet resistance, unaffected visible light transmittance, and good hydrophilicity. Compared with the uncrosslinked films, the tensile strength of the genipin-crosslinked ones was increased by 328.33 % (HBCC) and 397.83 % (H2ECC). More importantly, the crosslinked films had strong antibacterial activity against Staphylococcus aureus and Escherichia coli and were non-toxic to endothelial cells. The crosslinked films could effectively prolong the preservation time of strawberries, inhibit the decay of strawberries, and inhibit the reduction of vitamin C in strawberries. In conclusion, genipin-crosslinked HBCC and H2ECC films are potential fruit preservation materials.

Nanoporous Vesicular Membranes of Amphiphilic Polymers Containing Trans / Cis Isomers

Nanoporous Vesicular Membranes of Amphiphilic Polymers Containing <i>Trans</i> / <i>Cis</i> Isomers

Amphiphilic Perforated Honeycomb Films for Gravimetric Liquid Separation

AbstractThe separation of oil and water is an important technology for solving a wide range of water‐related problems such as purification of industrial wastewater. Herein, the fabrication of an extremely thin oil–water separation membrane is reported by precisely controlling the wettability of a honeycomb (HC) porous membrane. The developed membrane can easily separate water and oil by gravity and capillary force. The method of wettability control by UV–O3 treatment and the resultant change in the separated liquid are discussed. Amphiphilic perforated HC films with controlled wettability can be used in membranes that can separate different liquids according to their densities when the initial liquid added to the surface of the HC film is changed.

Low Fouling Polysulfobetaines with Variable Hydrophobic Content.

Amphiphilic polymer coatings combining hydrophilic elements, in particular zwitterionic groups, and hydrophobic elements comprise a promising strategy to decrease biofouling. However, the influence of the content of the hydrophobic component in zwitterionic coatings on the interfacial molecular reorganization dynamics and the anti-fouling performance is not well understood. Therefore, coatings of amphiphilic copolymers of sulfobetaine methacrylate 3-[N-2'-(methacryloyloxy)ethyl-N,N-dimethyl]-ammonio propane-1-sulfonate (SPE) are prepared which contain increasing amounts of hydrophobic n-butyl methacrylate (BMA). Their fouling resistance is compared to that of their homopolymers PSPE and PBMA. The photo-crosslinked coatings form hydrogel films with a hydrophilic surface. Fouling by the proteins fibrinogen and lysozyme as well as by the diatom Navicula perminuta and the green algae Ulva linza is assessed in laboratory assays. While biofouling is strongly reduced by all zwitterionic coatings, the best fouling resistance is obtained for the amphiphilic copolymers. Also in preliminary field tests, the anti-fouling performance of the amphiphilic copolymer films is superior to that of both homopolymers. When the coatings are exposed to a marine environment, the reduced susceptibility to silt incorporation, in particular compared to the most hydrophilic polyzwitterion PSPE, likely contributes to the improved fouling resistance.

Preparation and characterization of aqueous vitamin E/Soluplus® dispersions for film coating applications

Objective The goals of this study were to (1) delineate a technique to prepare stable aqueous vitamin E/Soluplus® dispersions; (2) characterize films cast from the aqueous dispersions; and (3) demonstrate the utility of the aqueous dispersions in fluid bed coating applications. This study demonstrated the feasibility of using vitamin E in the preparation of amphiphilic film withs potential use in delayed-release coating applications. Methods Low viscosity aqueous vitamin E/Soluplus® dispersions were prepared by first spray drying ethanolic vitamin E/Soluplus® solutions followed by high-shear homogenization of the solid dispersions in water. Concentrated (10%) aqueous dispersions containing 0%, 10%, 20%, and 30% of vitamin E in the binary blend with Soluplus® were then cast into films and characterized for contact angle and mechanical strength by texture analysis. Results All films were hydrophilic and homogenous, which confirmed the utility of vitamin E as a plasticizer for the Soluplus® polymer. The 0% and 10% films were brittle whereas the 30% were tacky. The 20% dispersion was subsequently used to coat acetaminophen granules by a fluidized bed process to a dry weight gain of 10–30%. When tested by a dissolution study, a delay in acetaminophen release was observed as a function of weight gain. Conclusion The results from this study demonstrated that it is feasible to produce stable vitamin E/Soluplus® aqueous dispersions to be used as solvent-free functional film coating materials.

Langmuir and Langmuir–Blodgett films of aromatic amphiphiles

ABSTRACT Amphiphiles are molecules that contain two discrete segments – a water-soluble hydrophilic part (head-group) and a water-insoluble hydrophobic part (tail). The structural variations possible with the head-group part are enormous and numerous amphiphiles have been designed in this way. On the other hand, the structural variations feasible for the hydrophobic tail part are rather limited. Saturated aliphatic hydrocarbon chains are predominantly found in most of the amphiphiles. Unsaturated aliphatic hydrocarbon chains (n-alkenyl or n-alkynyl chains) also serve as the hydrophobic tail part in many of the amphiphiles. Amphiphiles, wherein the hydrophobic tail part is made up of aromatic moieties (alone or in combination with aliphatic chains) are less frequently encountered compared to the other two types. Many of these aromatic amphiphiles, the focus of this review article, are known to form different types of assemblies including Langmuir and Langmuir-Blodgett (LB) films. In this review, we will provide an account of the different types of aromatic amphiphiles that have been reported and highlight their properties and applications at the air–water and air–solid interfaces.

Using Microemulsions: Formulation Based on Knowledge of Their Mesostructure.

Microemulsions, as thermodynamically stable mixtures of oil, water, and surfactant, are known and have been studied for more than 70 years. However, even today there are still quite a number of unclear aspects, and more recent research work has modified and extended our picture. This review gives a short overview of how the understanding of microemulsions has developed, the current view on their properties and structural features, and in particular, how they are related to applications. We also discuss more recent developments regarding nonclassical microemulsions such as surfactant-free (ultraflexible) microemulsions or ones containing uncommon solvents or amphiphiles (like antagonistic salts). These new findings challenge to some extent our previous understanding of microemulsions, which therefore has to be extended to look at the different types of microemulsions in a unified way. In particular, the flexibility of the amphiphilic film is the key property to classify different microemulsion types and their properties in this review. Such a classification of microemulsions requires a thorough determination of their structural properties, and therefore, the experimental methods to determine microemulsion structure and dynamics are reviewed briefly, with a particular emphasis on recent developments in the field of direct imaging by means of electron microscopy. Based on this classification of microemulsions, we then discuss their applications, where the application demands have to be met by the properties of the microemulsion, which in turn are controlled by the flexibility of their amphiphilic interface. Another frequently important aspect for applications is the control of the rheological properties. Normally, microemulsions are low viscous and therefore enhancing viscosity has to be achieved by either having high concentrations (often not wished for) or additives, which do not significantly interfere with the microemulsion. Accordingly, this review gives a comprehensive account of the properties of microemulsions, including most recent developments and bringing them together from a united viewpoint, with an emphasis on how this affects the way of formulating microemulsions for a given application with desired properties.

Phase behavior of surface films of SARA fractions extracted from heavy oil

Crude oil amphiphilics have been extensively investigated concerning their colloidal properties related to oilfield operation problems. The interfacial structure and elasticity of oil amphiphilic films built on fluid-fluid interfaces have a powerful effect on the stability and rheology of petroleum emulsions and foams. This work presents a description of interfacial films of amphiphilics extracted from petroleum at water-air interfaces using a Langmuir trough. The investigation evaluates surface pressure - area compression isotherms to describe properly the phase behavior of monolayers formed by SARA fractions on isothermal compression at different subphase pH. The SARA films displayed two distinct phase-transitions in different specific areas, according to the pH of the subphase. At pH 2, the surface pressure follows the order: asphaltene > aromatic > resin > saturate, for specific areas higher than 0.04 m2/mg. At neutral and basic pH, the previous order was changed to asphaltene > resin > aromatic > saturate. The surface pressure for asphaltene films was always higher than the surface pressure for other SARA fractions, which is in agreement with the higher surface activity of crude oil asphaltenes. The occurrence of the first phase transition of asphaltene films varies in the range 0.14–0.19 m2/mg with a maxima surface pressure (πmax) of 37.14 mN/m, whereas the second phase transition was held on range 0.069–0.099 m2/mg with a πmax = 55.23 mN/m. The modulus of elasticity (E) of asphaltene compressed-liquid films was found 65–80 mN/m (expect at pH 4, where E~40 mN/m), which is related to the most compressible films. On the other hand, maltene films of SARA fractions showed almost always modulus of elasticity lower than 20 mN/m for both expanded-liquid and compressed-liquid films. The description of the interfacial film nature must be a useful tool to forecast the film stability in the disperse systems as foams and emulsions according to the SARA composition.

Facile Fabrication of Amphiphilic and Asymmetric Films with Excellent Deformability for Efficient and Stable Adsorption Applications

AbstractIn this study, a facile way to prepare amphiphilic and asymmetric films with excellent mechanical properties for efficient and stable adsorption applications is reported. Non‐solvent induced phase separation technology is developed to fabricate porous asymmetric poly(ether‐block‐amide) composite films. These films have a unique structure composed of a solid surface, a microporous surface, and hierarchical porous core, hence exhibiting prominent mechanical properties with an elongation at break up to 317% and mechanical resilience. Before and after 50‐times cyclic stretching deformations, they still maintain intact porous structure, and their wetting angles of upper and lower surfaces to both water and cyclohexane are almost constant. Moreover, these films show excellent uptake for cyclohexane and water, and cyclic large deformations have little influence on the performance. It only takes 3 s to absorb 4 times of the weight of cyclohexane, while 1.8 times of water can be loaded within 134 s.

Amphiphilic Polymer Thin Films with Enhanced Resistance to Biofilm Formation at the Solid–Liquid–Air Interface

AbstractBiofouling at the solid–liquid–air interface poses a serious threat to public health and environmental sustainability. Despite the variety of antifouling materials developed, few have proven to resist fouling at the three‐phase contact line. In fact, antifouling at the liquid–solid interface and the air–solid interface call for opposite surface properties—hydrophilic for the former and hydrophobic for the latter. By devising a new design strategy, one that maximizes the mismatch of surface energies of comonomers for dynamic chain reorientation at the three‐phase contact line, an antifouling amphiphilic copolymer is obtained. The novel amphiphilic copolymer reduces the formation of biofilms by Pseudomonas aeruginosa and outperforms a zwitterionic polymer, the current leading antifouling chemistry. The copolymer is synthesized using initiated chemical vapor deposition (iCVD), which leads to molecular‐level heterogeneities composed of zwitterionic and fluorinated moieties by avoiding undesirable surface tension effects. Atomic force microscopy, x‐ray diffractometry, and Fourier transform infrared spectroscopy confirm the copolymer's amphiphilicity and lack of microphase separation. Scanning electron microscopy provides visual confirmation of the diminished biofilm growth. The versatile iCVD technique is amenable to a range of substrates and enables the application of this new material to food processing, healthcare, and underwater performance.

Efficiency Boosting of Surfactants with Poly(ethylene oxide)-Poly(alkyl glycidyl ether)s: A New Class of Amphiphilic Polymers.

Twenty years ago, it was found that adding small amounts of amphiphilic block copolymers like poly(ethylene propylene)-co-poly(ethylene oxide) (PEP-b-PEO) to microemulsion systems strongly increases the efficiency of medium-chain surfactants to solubilize water and oil. Although being predestined to serve as a milestone in microemulsion research, the effect has only scarcely found its way into applications. In this work, we propose new types of efficiency boosters, namely, poly(ethylene oxide)-poly(alkyl glycidyl ether carbonate)s (PEO-b-PAlkGE) and their "carbonated" poly(ethylene oxide)-poly(carbonate alkyl glycidyl ether) analogs. Their synthesis via anionic ring-opening polymerization (AROP) from commercially available long-chain alkyl glycidyl ethers (AlkGE) and monomethoxypoly(ethylene glycol)s as macroinitiators can be performed at low cost and on a large scale. We demonstrate that these new PEO-b-PAlkGE copolymers with dodecyl and hexadecyl side chains in the nonpolar block strongly increase the efficiency of both pure and technical-grade n-alkyl polyglycol ether surfactants to form microemulsions containing pure n-alkanes or even technical-grade waxes, a result that could be of interest for industrial applications where reduced surfactant needs would have significant economic and ecological implications. For n-decane microemulsions, the boosting effect of PEO-b-PAlkGE and PEP-b-PEO polymers can be scaled on top of each other, when plotting the efficiency semilogarithmically versus the polymeric coverage of the amphiphilic film. Interestingly, a somewhat different scaling behavior was observed for n-octacosane microemulsions at elevated temperatures, suggesting that the polymers show less self-avoidance and rather behave as almost ideal chains. A similar trend was found for the increase of the bending rigidity κ upon polymeric coverage of the amphiphilic film, which was obtained from the analysis of small-angle neutron scattering (SANS) measurements.