Hydrophilic Film Research Articles

Automatically Programmable Shape-Memory Polymers Based on Asymmetric Swelling of Bilayer Structures.

Shape-memory polymers (SMPs) possess the capability to change shapes upon stimulation; however, the programming process that determines the temporary shape cannot proceed without external manipulation, which may greatly affect the shape complexity, accuracy, and reproducibility. Here, an automatically programmable SMP (AP-SMP) based on asymmetric swelling of bilayer SMP structures is demonstrated without external manipulation. In the automatic programming process, the AP-SMP can be deformed by the swelling of its hydrophilic hinge film in warm water to a temporary shape, which could be fixed by the glass transition of the two SMP films through cooling and drying in air. Owing to the uniqueability, many complex shapes can be easilycustomized through diverse design strategies. Moreover, the AP-SMPs can reversibly transform between the permanent and temporary shapes, and both shapes are free-standing in normal conditions. The automatic programming of AP-SMPs may greatly expand the potential application range of SMPs.

Electricity generation from water droplets via capillary infiltrating

Electricity generation from the interaction between water and carbon materials is a new approach in the pursuit of high-efficiency energy conversion. Here, we report that a water droplet dropping onto a piece of porous carbon film can spontaneously generate electricity under ambient conditions. Twelve 5-μL water droplets can generate a voltage up to 5.2 V and illuminate a liquid crystal display. The voltage can be controlled by modulating the direction of the droplet infiltration, the zeta potential of the porous carbon, and the ion concentration. The results demonstrate that a hydrophilic porous carbon film with water droplets may function as a cost-effective electricity generator for harvesting energy from natural resources.

Biomaterials Based on Electrospun Chitosan. Relation between Processing Conditions and Mechanical Properties.

In this paper, it is shown that pure chitosan nanofibers and films were prepared with success in 0.5 M acetic acid as solvent using poly (ethylene oxide) (PEO) at different yields, allowing electrospinning of the blends. After processing, a neutralization step of chitosan followed by water washing is performed, preserving the initial morphology of chitosan materials. The influence of the yield in PEO in the blend on the degree of swelling and hydrophilicity of films and nanofibers is demonstrated. Then, the mechanical behavior of blended nanofibers and films used as reference are determined for small stress applied in the linear domain by DMA and by uniaxial traction up to rupture. The dried and wet states are covered for the first time. It is shown that the mechanical properties are increased when electrospinning is performed in the presence of PEO up to a 70/30 chitosan/PEO weight ratio even after PEO extraction. This result can be explained by a better dispersion of the chitosan in the presence of PEO.

Zero-order release of poorly water-soluble drug from polymeric films made via aqueous slurry casting

In spite of significant recent interest in polymeric films containing poorly water-soluble drugs, dissolution mechanism of thicker films has not been investigated. Consequently, release mechanisms of poorly water-soluble drugs from thicker hydroxypropyl methylcellulose (HPMC) films are investigated, including assessing thickness above which they exhibit zero-order drug release. Micronized, surface modified particles of griseofulvin, a model drug of BSC class II, were incorporated into aqueous slurry-cast films of different thicknesses (100, 500, 1000, 1500 and 2000 μm). Films 1000 μm and thicker were formed by either stacking two or more layers of ~500 μm, or forming a monolithic thick film. Compared to monolithic thick films, stacked films required simpler manufacturing process (easier casting, short drying time) and resulted in better critical quality attributes (appearance, uniformity of thickness and drug per unit area). Both the film forming approaches exhibited similar release profiles and followed the semi-empirical power law. As thickness increased from 100 μm to 2000 μm, the release mechanism changed from Fickian diffusion to zero-order release for films ≥1000 μm. The diffusional power law exponent, n, achieved value of 1, confirming zero-order release, whereas the percentage drug release varied linearly with sample surface area, and sample thickness due to fixed sample diameter. Thus, multi-layer hydrophilic polymer aqueous slurry-cast thick films containing poorly water-soluble drug particles provide a convenient dosage form capable of zero-order drug release with release time modulated through number of layers.

Surface modification via atmospheric cold plasma (ACP): Improved functional properties and characterization of zein film

In the present study, the nonhazardous atmospheric cold plasma (ACP) technique was introduced to improve the surface hydrophilicity and mechanical strength of zein film. The results indicated that the surface hydrophilicity was significantly increased after ACP treatment, with a drop of contact angle from 72.85 ± 2.33° (untreated) to 48.42 ± 1.57° (ACP–60 s). Increased surface roughness and enrichment of the oxygen- and nitrogen-containing groups were responsible for this modification. As the X-ray photoelectron spectroscopy (XPS) results shown, the O1 s and N1 s peak intensity was dramatically enhanced after 30 s ACP treatment with an increased O/C ratio from 0.64 to 1.09. Storage in ambient environment for an extra 24 h of treated film could further reduce the contact angle. With the treatment time extending, enhanced tensile strength (TS) and flexibility were observed in zein films, accompanied by improving thermal properties, which indicated the cross-linking within protein matrix. Moreover, ACP treatment could significantly decrease the water vapor permeability (WVP) due to the increasing tortuosity of the diffusion pathway after plasma treatment. The secondary structure in amide I band (1600–1700 cm−1) indicated that there was a transformation from β-turn and α-helix into β-sheet induced by ACP treatment. This research opens up new opportunities that ACP could be developed as a modification method of zein film for better utilization in packaging industry.

Enhancement of graft density and chain length of hydrophilic polymer brush for effective marine antifouling

ABSTRACT2‐Hydroxyethyl methacrylate polymer brushes with various grafting densities and chain lengths were prepared through surface‐initiated atom transfer radical polymerization. X‐ray photoelectron spectra, ellipsometry measurement, contact angle measurement, and atom force microscope were used to characterize the prepared polymer brush. The biofouling assays of polymer brush were investigated by adhesion of Dunaliella tertiolecta, Navcular sp., and Bovine Serum Albumin protein and by static marine immersion field test. Besides, hydroxyl and sulfonate‐terminated self‐assembled monolayers, anionic charged 3‐sulfopropyl methacrylate potassium salt polymer brush were prepared for comparison. Results suggest that the settlement of microorganisms can be largely reduced by polymer with enough polymer chain length and grafting density. More importantly, static immersion field tests indicate that hydrophilic polymer film with enough hydration layer thickness is necessary for long‐term marine antifouling application. This comprehensive investigation is of great importance to understanding their influence on the adhesion of marine microorganism. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46232.

Highly transparent, flexible and hydrophilic ZnS thin films prepared by a facile and environmentally friendly chemical bath deposition method

Growth of highly transparent and hydrophilic ZnS thin films on flexible polymeric and glass substrates has been performed using an environmentally friendly chemical bath deposition method with an ammonia and thioacetamide free reaction solution. Deposition time effect on surface morphology, structure and optical properties of the ZnS thin films has been investigated by field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffractometer (XRD), ultraviolet-visible light (UV–vis) spectroscopy, and photoluminescence (PL) spectroscopy. Also, the chemical composition of the prepared films has been studied in detail by energy-dispersive X-ray spectrometer (EDX), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. TEM images show that the ZnS films consisted of small nanocrystals with diameters ≤5 nm. Moreover, the water contact angles, 38.5° and 25.4° for ZnS films deposited on PS and on glass substrates, respectively, indicate a highly hydrophilic nature. Undoubtedly, the chemical analysis shows the formation of the films with a chemical composition of ZnS0.89, lacking impurities such as ZnO and/or Zn (OH)2. Additionally, FE-SEM images show a homogenous deposition over a very large surface area substrates. Ultimately, the obtained photoluminescence spectrum indicates a strong and broad emission peak ranging from 400 to 600 nm, which are due to deep levels or trap state defects in the crystalline structure of the ZnS films.

Influence of physical plasma etching treatment on optical and hydrophilic MgF2 thin film

In this study, MgF2 thin film was prepared on glass substrate by thermal evaporation method. After that surface of the MgF2 thin film was improved using physical plasma etching treatment by plasma enhanced chemical vapor deposition (PECVD) equipment. Structural properties and surface morphology and roughness of the thin films were evaluated by GIXRD, FESEM and AFM, respectively. Also optical properties were investigated throughout measurement of transmission spectra and refractive index in visible region by use of UV/vis spectrometer and ellipsometer, respectively. Water contact angles of the surfaces were measured by water contact analyzer. Results of the research indicated that transparency of the MgF2 thin films remind without change and hydrophilic properties of the MgF2 thin films turned to superhydrophilic properties after physical plasma etching treatment.

Accelerated Transport of Particles in Confined Channels with a High Roughness Amplitude.

We investigate the pressure-driven transport of particles 200 or 300 nm in diameter in shallow microfluidic channels ∼1 μm in height with a bottom wall characterized by a high roughness amplitude of ∼100 nm. This study starts with the description of an assay to generate cracks in hydrophilic thin polymer films together with a structural characterization of these corrugations. Microfluidic chips of variable height are then assembled on top of these rough surfaces, and the transport of particles is assessed by measuring the velocity distribution function for a set of pressure drops. We specifically detect anomalous transport properties for rough surfaces. The maximum particle velocity at the centerline of the channel is comparable to that obtained with smooth surfaces, but the average particle velocity increases nonlinearly with the flow rate. We suggest that the change in the boundary condition at the rough wall is not sufficient to account for our data and that the occurrence of contacts between the particle and the surface transports the particle away from the wall and speeds up its motion. We finally draw perspectives for the separation by field-flow fractionation.

The role of water in the anomalies of pyro- and thermodepolarization properties of pyroactive polymer films at stepwise heating

The paper presents the results of investigations of the temperature dependencies of pyroelectric coefficient and thermodepolarization currents of pyroelectric polymer films (hydrophobic VDF/TrFE copolymer and hydrophilic Langmuir films of azo compounds), which were prepared using water. The anomalies of these properties were observed at 4, 28, 35, 45°C for films of azo compounds and 20, 35, 49, 72 and 100°C for VDF/TrFE. These temperature points are close to temperatures of anomalies of physical properties of water. At the listed temperature points, water clusters and the molecule itself are destroyed. Similar anomalies have been previously observed in crystallohydrates, “polymer-water” systems and ferroelectrics of Triglycine Sulphate family, in the structure of which there is a network of OH…O hydrogen bonds of the same length as in water. The key property of the hydrogen bond is the presence of discrete protons energy levels, which at stepwise heating (slow kinetics) leads to the transformation or destruction of the hydrogen-bonding network, as well as to the refilling of proton energy levels in the double minimum potential, the release of deep traps, and to the change of charge carrier types, their mobility and conducting paths.

Polymeric chemosensor for the detection and quantification of chloride in human sweat. Application to the diagnosis of cystic fibrosis

We have developed a new extremely hydrophilic polymeric film suitable for the detection and quantification of chloride in human sweat directly on the skin. The film, or membrane, has chemically anchored 6-methoxyquinoline groups as chloride responsive fluorescent motifs. We have prepared the sensory material from a standard vinyl copolymer, by a convenient and easy solid-phase reaction. The sensory material has a water swelling percentage of 700%, facilitating an immediate detection of chloride, is reusable for at least 6 cycles and can be handled without care by unskilled persons. The initially high fluorescence of the material decreases in the presence of chloride, allowing the quantification of chloride concentration by using the colour definition of a digital picture or a fluorimeter. The suitability of the material to perform quantitative chloride analysis of human sweat by putting it in contact with the skin offers promise for its application in the sweat test used for the diagnosis of cystic fibrosis (CF).

A newly developed lithium cobalt oxide super hydrophilic film for large area, thermally stable and highly efficient inverted perovskite solar cells

A new inorganic hole transporting layer, a sputtering made LiCoO2 film, was developed and used in an inverted perovskite solar cell (PSC) and sub-module (PSM).

Microstructure and physical properties of nano-biocomposite films based on cassava starch and laponite

The aim of this research was to study the effects of laponite concentrations on some properties of nano-biocomposite films based on cassava starch, focusing mainly the relation between the properties of the surface microstructure and roughness, water contact angle and gloss. Nano-biocomposite films were produced by casting. We analyzed gloss, color, opacity, water contact angle, crystallinity by X-ray diffraction, and microstructure by scanning electron microscopy and atomic force microscopy. Texture parameters (energy, entropy and fractal dimension) were extracted from micrographs. We observed a great impact of laponite in the morphology of nano-biocomposite films. Texture parameters correlated with surface heterogeneity and roughness. Finally, surface roughness affected the surface hydrophilicity of nano-biocomposite films. Laponite platelets were exfoliated and/or intercalated with amylose and amylopectin chains. This research reports new information on the effects of laponite concentrations on the morphological, optical and wetting properties of nano-biocomposite films aiming future industrial applications.

Development of a Technique and Investigation of Capacitance Characteristics of Electrode Materials for Supercapacitors Based on Nitrogen-Doped Carbon Nanotubes

Carbon nanotubes are widely employed as catalyst supports and electrode materials. In our earlier studies, capacitance characteristics of carbon nanotubes (CNTs) and nitrogen-doped carbon nanotubes (N-CNTs) were measured. Voltammetric curves obtained for nitrogen-doped nanotubes in an acid electrolyte showed pseudocapacitance peaks that were caused by electrochemical processes involving nitrogen-containing functional groups. In this study, measurements were made in a two-electrode cell of a supercapacitor with a hydrophilic polypropylene PORP-A1 film serving as a separator in alkaline (6 M KOH solution) and acid (1 M H2SO4 solution) electrolytes using a PARSTAT 4000 potentiostat/galvanostat. A technique was developed to estimate the contribution of electrical double layer (EDL) by subtracting pseudocapacitance from total capacitance of a cell using the Origin 9 software. The contribution of EDL and pseudocapacitance to the capacitance of supercapacitor cells was estimated. The highest capacitance of an electrode material equal to 97.2 F/g (including the EDL capacitance of 65 F/g) was reached for nanotubes doped with 8.5% of nitrogen in an acid electrolyte at a potential scanning rate of 10 mV/s.

Synthesis of a bio‐inspired catechol/phosphorylcholine surface modifier and characterization of its surface properties

ABSTRACTBiocompatible and blood‐compatible surface modification is urgently needed for stainless steel (SUS)‐based human implant devices to avoid inflammation and biofouling. To this end, the use of polymeric surface modifiers, whose surface properties are specifically tailored, is a promising approach since this approach minimizes the impact on device's mechanical properties. However, adhesion between the device and surface modifier is relatively weak, since van der Waals forces are employed, leading to low device durability. To address this issue, this work functionalized poly(ɛ‐caprolactone)‐b‐[poly(α‐chloride‐ɛ‐caprolactone)‐b‐poly(2‐methacryloyloxyethyl phosphorylcholine)]2 (PCL‐b‐(PCL‐Cl‐b‐PMPC)2) with catechol groups via a nucleophilic substitution, whereby the catechol functionalization was optimized. The resultant surface modifier showed strong adhesion toward SUS surfaces, forming a smooth and uniform hydrophilic polymeric film that reduced SUS fouling (i.e., protein). Notably, no significant changes of adhesion between the SUS and thin films (thin film) were observed after immersion for 45 days in a pH 7.4 phosphate buffer solution. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 38–49

Experimental study of self-cleaning property of titanium dioxide and nanospray coatings in solar applications

Nowadays, the urgent need to replace fossil fuels with renewable energy is no secret. Therefore, researching in this area and developing the infrastructures necessary for the optimized utilization of these types of energy, are rising sharply. Among different kinds of renewable energy, due to easy access, solar energy has received special attention and extensive studies have been done, in order to increase the efficiency of the solar collectors and PV panels. One of the prime problems of solar systems in arid regions is the accumulation of dust on transparent surfaces, followed by an intensive drop in the transmission coefficient. In the present study, in a 70-day test period, up to 22% transmission coefficient loss, caused by the accumulation of dust on the surface, was observed. Thus, in order to solve this problem, Nanocoatings were deposited on glass samples to create self-cleaning property. A nanospray was used to create a hydrophobic film on the surface and TiO2 was coated in three different thickness to create a hydrophilic film on sample surfaces. Test results showed that these surface modifications have a significant impact in the reduction of dust accumulation and the loss of the transmission coefficient. Although there was no rain during the test, for samples with surface modification, the transmission coefficient drops were noticeably reduced. After rain simulation, the results indicate that transmission loss reduced from 22% to 0.5% and dust settlement problem was almost completely solved.

A simple method for the sonochemical synthesis of PVA/ZrO2-vitamin B1 nanocomposites: Morphology, mechanical, thermal and wettability investigations

Poly(vinyl alcohol) (PVA) based nanocomposites (NCs) filled by various weight percent of modified ZrO2 nanoparticles (NPs) with vitamin B1 (VB1) up to 7wt% were fabricated via ultrasonication method then was cast to thin films. The ultrasonication was applied for the preparation and modification process asan easy, safe and fast method. Ultrasonic was responsible for great homogeneities of NPs into PVA matrix, which could not be achieved by mechanical or magnetically stirring. The creation of polymer NCs and changes in the structural properties were examined by X-ray diffraction. FT-IR spectroscopy indicated the possible interactions of the ZrO2-VB1 NPs with the PVA backbones and also, existence of absorption bands related to PVA and ZrO2 NPs in the NC structures. The distribution of nano-fillers and uniform morphology of the NCs showed that the ZrO2-VB1 NPs were homogeneously dispersed in the polymer matrix in the nanosized scale. UV–Vis analysis shown that the the optical absorption were improved by evolution of ZrO2-VB1 NPs content. The tensile strength of PVA film was increased significantly with increasing the ZrO2-VB1 NPs content. Thermal gravimetric analysis confirmed that NCs displayed higher thermal stability than the pristine PVA. Also, water contact angle analysis indicated that the hydrophilicity of NC films was enhanced with increasing the concentration of ZrO2 NPs.

Digital quantification of DNA via isothermal amplification on a self-driven microfluidic chip featuring hydrophilic film-coated polydimethylsiloxane

Loop-mediated isothermal amplification (LAMP) is a DNA amplification approach characterized by high sensitivity and specificity. In “digital LAMP”, small quantities of both template DNA and reagents are encapsulated within a droplet or microwell, allowing for analysis of precious nucleic acid samples in shorter amounts of time relative to traditional DNA amplification protocols (e.g., PCR) with an improved limit of detection. In this study, an integrated, self-driven microfluidic chip was designed to carry out digital LAMP. The entire quantification process could be automatically performed on this chip via capillary forces enabled through microwells comprised of polydimethylsiloxane (PDMS) surfaces coated with a hydrophilic film; no external pumps were required. Moreover, digitized droplets could be separated from each other by normally-closed microvalves. The contact angle of the hydrophilic film-coated PDMS surface was only 14.3°. This is the first time that a rapid (30min) and simple method has been used to create hydrophilic PDMS surfaces that allow for digital LAMP to be performed in a self-driven microfluidic device. As a proof of concept, amplification of a gene specific to a vancomycin-resistant Enterococcus strain was performed on the developed microfluidic chip within 30min, and the limit of detection was only 11 copies with a volume of 30μL. This device may therefore become a promising tool for clinical diagnosis and point-of-care applications.

Hydrophobic, Flexible, and Lightweight MXene Foams for High-Performance Electromagnetic-Interference Shielding.

Ultrathin, lightweight, and flexible electromagnetic-interference (EMI) shielding materials are urgently required to manage increasingly serious radiation pollution. 2D transition-metal carbides (MXenes) are considered promising alternatives to graphene for providing excellent EMI-shielding performance due to their outstanding metallic electrical conductivity. However, the hydrophilicity of MXene films may affect their stability and reliability when applied in moist or wet environments. Herein, for the first time, an efficient and facile approach is reported to fabricate freestanding, flexible, and hydrophobic MXene foam with reasonable strength by assembling MXene sheets into films followed by a hydrazine-induced foaming process. In striking contrast to well-known hydrophilic MXene materials, the MXene foams surprisingly exhibit hydrophobic surfaces and outstanding water resistance and durability. More interestingly, a much enhanced EMI-shielding effectiveness of ≈70 dB is achieved for the lightweight MXene foam as compared to its unfoamed film counterpart (53 dB) due to the highly efficient wave attenuation in the favorable porous structure. Therefore, the hydrophobic, flexible, and lightweight MXene foam with an excellent EMI-shielding performance is highly promising for applications in aerospace and portable and wearable smart electronics.

Biomineralized diamond-like carbon films with incorporated titanium dioxide nanoparticles improved bioactivity properties and reduced biofilm formation

Recently, the development of coatings to protect biomedical alloys from oxidation, passivation and to reduce the ability for a bacterial biofilm to form after implantation has emerged. Diamond-like carbon films are commonly used for implanted medical due to their physical and chemical characteristics, showing good interactions with the biological environment. However, these properties can be significantly improved when titanium dioxide nanoparticles are included, especially to enhance the bactericidal properties of the films. So far, the deposition of hydroxyapatite on the film surface has been studied in order to improve biocompatibility and bioactive behavior. Herein, we developed a new route to obtain a homogeneous and crystalline apatite coating on diamond-like carbon films grown on 304 biomedical stainless steel and evaluated its antibacterial effect. For this purpose, films containing two different concentrations of titanium dioxide (0.1 and 0.3g/L) were obtained by chemical vapor deposition. To obtain the apatite layer, the samples were soaked in simulated body fluid solution for up to 21days. The antibacterial activity of the films was evaluated by bacterial eradication tests using Staphylococcus aureus biofilm. Scanning electron microscopy, X-ray diffraction, Raman scattering spectroscopy, and goniometry showed that homogeneous, crystalline, and hydrophilic apatite films were formed independently of the titanium dioxide concentration. Interestingly, the diamond-like films containing titanium dioxide and hydroxyapatite reduced the biofilm formation compared to controls. A synergism between hydroxyapatite and titanium dioxide that provided an antimicrobial effect against opportunistic pathogens was clearly observed.