Hydrophilic Film Research Articles

PH-Responsive Copolymer Films Prepared by Surface-Initiated Polymerization and Simple Modification.

We report the preparation of pH-responsive, ester/carboxylic acid random copolymer films via simple modification of poly(norbornene diacyl chloride) (pNBDAC), prepared via surface-initiated ring-opening metathesis polymerization, with mixtures of water and ethanol to form carboxylic acid and ethyl ester side groups. The pNBDAC film serves as a compositionally versatile platform to controllably obtain copolymers with multiple functionalities. In modifying the pNBDAC to form the copolymer film, ethanol exhibits a significantly higher reactivity with acyl chloride groups within the film than does water. The magnitude and range of the pH-responsive performance are highly dependent on the carboxylic acid content in the copolymer films, which demonstrates the effect of film hydrophilicity on the pH-responsive switching of ionic barrier properties. The resistance of the film against ion transfer can be decreased by a factor of 104 through pH change, demonstrating pH-induced switching from hydrophobic and insulating to swollen and ion-permeable films. The interactions of the copolymer films with water at different pH values were also explored. When the copolymer contains 34% carboxylic acids, a 4× greater film thickness is obtained in high pH solution than in low pH solution due to ionically driven water swelling. The reversibility of the pH-responsive performance of these copolymer films is high based on measurements using quartz crystal microbalance with dissipation (QCM-D).

Preparation and characterization novel dioctyl terephthalate blended polyvinyl alcohol-composite films incorporated with the graphene oxide and silver nanoparticles

Dioctyl terephthalate is of great interest as a replacement for the phthalate plasticizers such as dioctyl phthalate and diisononyl phthalate due to its orthophthalate-free and non-carcinogenic properties. This study focused on the production, characterization and optimization of the quality characteristics of its film properties, such as the mechanical, hydrophilic and thermal properties of dioctyl terephthalate-blended polyvinyl alcohol composites modified with graphene oxide and silver nanoparticles using TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) based Taguchi Method. Dioctyl terephthalate has brought remarkable features, such as high elastic modulus, and hydrophilic and thermal stability to the polyvinyl alcohol matrix. The optimum Dioctyl terephthalate -blended polyvinyl alcohol films have a 2.26 times lower contact angle and a 13.41 times higher elastic modulus than the reference polyvinyl alcohol film. Dioctyl terephthalate should be preferentially used to manufacture more durable and hydrophilic composite films such as fibers, disposable underpad or industrial swab, instead of toxic phthalate plasticizers.

The synthesis of bayberry-like mesoporous TiO2 microspheres by a kinetics-controlled method and their hydrophilic films

Bayberry-like mesoporous TiO2 hydrophilic films with high surface roughness and high density of surface hydroxyl groups.

Chemical and physical reinforcement of hydrophilic gelatin film with di-aldehyde nanocellulose

Gelatin is a representative hydrophilic protein material with remarkable biocompatibility and biodegradability. From the aspect of materials processing, gelatin also has the advantage that its entire fabrication process can be performed in an aqueous solution. However, practical application of various gelatin materials—in particular gelatin films—has thus far been limited because of their weak mechanical properties and vulnerability under aqueous environments. To overcome these disadvantages, both physical reinforcement approaches and chemical cross-linking agents have been tested. However, little research has been done to make these two roles work at the same time. In this study, cellulose nanocrystals containing aldehyde groups were prepared via a periodate oxidation process and used for cross-linkable reinforcement of gelatin-based bio-composite films. The results revealed that the di-aldehyde cellulose nanocrystal (D-CNC) could react and covalently cross-link with the amine group of the gelatin molecules via Schiff base formation and compared with neat CNC. The gelatin bio-composite film reinforced with the prepared D-CNC exhibited excellent tensile properties and water resistance, and its mechanical and hydrophilic properties could be easily controlled by adjusting the D-CNC content and was greater than addition of same amount in CNC. Therefore, D-CNC will facilitate the widespread use of existing water-soluble polymers, especially natural hydrophilic proteins and can be used in conventional application fields such as the food, pharmaceutical, and biomedical industries.

Nutrient diffusion control of fertilizer granules coated with a gradient hydrophobic film

A gradient hydrophobic film was prepared to improve the controlled release performance of film-coated fertilizers. A polyurethane (PU) was copolymerized with hydroxypropyl-terminated polydimethylsiloxane (HP-PDMS) at different ratios to produce a film with different levels of hydrophobicity. A film with a gradient hydrophobicity was prepared by successively coating a copolymer of PDMS/PU at different ratios. The urea diffusion rate via an inner hydrophilic and outer hydrophobic (InHL-OutHB) gradient hydrophobic film was reduced significantly, compared with that via a uniform hydrophilic or hydrophobic film. For the InHL-OutHB gradient hydrophobic film, the release period of the coated urea with a coating amount of 4 % was over 60 days, which was significantly longer than that of the uniform film.

Relative humidity sensor based on no-core multimode interferometer coated with Al2O3-PVA composite films

Abstract Herein, a simple relative humidity (RH) fiber sensor based on a multimode interferometer (MMI) with aluminum oxide nanoparticles (Al2O3 NPs) and polyvinyl alcohol (Al2O3-PVA) composite was fabricated and experimentally demonstrated. The sensor was fabricated by splicing a no-core fiber (NCF) segment between two single-mode fibers (SMF). The chemical etching method has been used with hydrofluoric (HF) acid to prepare diverse NCF diameters. This was proposed to expand the evanescent fields and enhance sensor sensitivity. A hydrophilic sensitive film based on Al2O3-PVA was coated on the surface of NC fiber using the cast-drop and evaporation technique. By altering the ambient humidity, water adsorption into the Al2O3 nanostructures occurs and therefore, the refractive index (RI) of the coated film varies inducing a 38.9 nm wavelength shift in the output spectra. The results showed that a maximum sensitivity of 0.587 nm/%RH has been achieved as the percentage of the RH increases from 30% to 100%. The simple fabrication and the high sensitivity of this sensor may prompt many potential applications in the fields of biology and chemistry.

SNR-enhanced temperature-insensitive microfiber humidity sensor based on upconversion nanoparticles and cellulose liquid crystal coating

Combining upconversion nanoparticles (UCNPs) and cellulose liquid crystal (CLC) film, a microfiber relative humidity (RH) sensor with enhanced signal-to-noise ratio (SNR) is proposed. The sensor head consist of a microfiber successively coated with a UCNP fluorescent layer and a hydrophilic CLC film layer. The UCNP fluorescence spectra is located in the photonic band gap of the CLC film, resulting in mirrorless low threshold lasing emission. The addition of the CLC film enhances the SNR by 12 dB. The RH response and the temperature-insensitivity are both experimentally verified. The sensitivity of the proposed sensor is 284.75 pm/%RH. It is a promising structure for highly sensitive and accurate RH monitoring.

Sodium alginate/poly(4-vinylpyridine) polyelectrolyte multilayer films: Preparation, characterization and ciprofloxacin HCl release

Polyelectrolyte multilayer (PEC) films of sodium alginate (Na-Alg) and poly(4-vinylpyridine) (P4VP) were prepared and were loaded with an antibacterial agent, ciprofloxacin HCl (CIP.HCl) aiming to design new hydrophilic films with controlled physicochemical properties and drug release behaviour that may find application as components of transdermal drug delivery systems. The PEC films were characterized by SEM, XRD, TGA, AFM and FTIR spectroscopy. The hydrophilicity of the PEC films was examined by using contact angle measurement. The number of layers and the nature of the outer layer affect the physicochemical characteristics, CIP.HCl loading and release behaviour of the films. The three layer film PEC-3, which is composed of Na-Alg outer layer deposited on a P4VP/Na-Alg double layer, is characterized by the lowest roughness (Rq = 16.3 nm) and the most hydrophilic surface with a contact angle value of 38.1° among all other films. Its crystallinity index is 0.36, and starts to degrade at 195 °C. It exhibits 130–135% equilibrium swelling capacity in acid buffer and water respectively. PEC-3 is the film with the highest drug loading capacity and drug loading efficiency values of 3.51% and 87% respectively. A cumulative drug release of 65% is obtained from PEC-3 within 24 h in pH = 1.2 buffer solution.

Co-modification of polydopamine and KH560 on g-C3N4 nanosheets for enhancing the corrosion protection property of waterborne epoxy coating

In this work, the hydrophilic organic films were successfully coated on g-C3N4 nanosheets through facile co-modification of dopamine (DA) and silane coupling agent (KH560). The co-modification of polydopamine (PDA) and KH560 on lamellar g-C3N4 greatly enhanced dispersion of g-C3N4 in aqueous solution and dramatically improved the compatibility and interfacial interaction with waterborne epoxy. The effect of incorporating modified g-C3N4 nanosheets into waterborne epoxy on anticorrosion performance for P110 steel substrates were demonstrated through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and salt spray test. The results revealed that the |Z|0.01Hz value and percentage coating resistance (Rc) gain (ηc%) of nanocomposite coating increased by 977% and 90.72% with the addition of modified g-C3N4 nanosheets in comparison with pure waterborne epoxy coating, exhibiting outstanding anticorrosion abilities. The reinforced anticorrosion performances of nanocomposite coating could be attributed to the notable shielding effect and well dispersibility of modified g-C3N4 nanosheets.

Effects of electric field and temperature on the shape of chlorophyll aggregates in casting films

We have prepared chlorophyll (Chl) casting films and characterized the effects of temperature and electric field on the fractal forms of Chl aggregates formed therein. The amount of fractal aggregates increased with increasing temperature. Their fractal dimensions (1.54–1.66) were close to those predicted by the diffusion-limited aggregation model. The surface morphology change of Chl films with temperature did not affect their wettability, i.e., these films remained hydrophilic, exhibiting contact angles θC of 35.3 ± 4.9°. The application of an electric field induced a Brownian-tree to chain-shaped aggregate form change, which was rationalized by the effect of electric drag on diffusion of Chl molecules. In contrast to the case of temperature-induced morphology change, the corresponding variation caused by the applied electric field have changed the film wettability and turned the originally hydrophilic (θC = 35.3 ± 4.9°) films into hydrophobic (θC = 86.6 ± 4.0°) ones. This find was consistent with the change in shape of the fractal aggregates.

Developing a highly pH-sensitive ĸ-carrageenan-based intelligent film incorporating grape skin powder via a cleaner process

An intelligent film was prepared from ĸ-carrageenan blended with hydroxypropyl methylcellulose and directly adding anthocyanins-rich grape skin powder (GSP) as the indicator with an extraction-free process. The films were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and observed by stereo microscope and Scanning electron microscope. The light transmittance, water-adsorption and mechanical properties were determined and tests monitoring pork freshness were conducted to evaluate its potential applications. The results show that the GSP distribution uniformity in the films decreased with GSP content increased; GSP formed new hydrogen bonds with matrix molecules and the cross-sections of the films were smooth and continuous. The appropriate addition of GSP can enhance the compatibility of the matrix, but decrease the film hydrophilicity. With GSP content increasing from 0% to 8%, the light transmittance decreased from 83.10% to 42.89% at 600 nm, and EB% and TS of the films decreased from 19.65% to 11.30% and from 20.96 MPa to 14.25 MPa, respectively. The film became blue-green when the pH reached 7, indicating that it is highly pH-sensitive and the film changed from purple to green when TVB-N was 14.63 mg/100 g, suggesting that it is intelligent for monitoring the freshness of the pork. This study offers a clean path to prepare a highly pH-sensitive film for indicating food freshness.

Hydrophilic thin films formation on AZ31 alloys by hydrothermal treatment in silicate containing solution and the evaluation of corrosion protection in phosphate buffered saline

Magnesium alloys have been widely studied as biodegradable implants for orthopedic applications due to their more suitable mechanical and biological properties. However, Mg and its alloys themselves don’t have high hydrophilicity considered to be effective in improving the osteoconductivity of implanted materials. The drastic degradation rate of Mg alloys would also cause potential harm to the human body. With the aim to promote the hydrophilicity and corrosion resistance of Mg alloys, thin film consisting of magnesium hydroxide with silicate was synthesized by hydrothermal treatment in the alkaline solution of sodium hydroxide and sodium silicate at 423 K. The physical properties of thin films were estimated by SEM, XRD, XPS, tape peeling test and water droplet contact angle (WCA), and corrosion properties were evaluated by polarization curves and impedance measurements (EIS) in PBS solution. Mg(OH)2 was found to be the main composite of the film with little of MgO coexisted. Si was detected on the surface of the film layer, based on XPS results. The addition of silicate during hydrothermal treatment would greatly improve the hydrophilicity and its stability in the air environment. The Mg(OH)2 film containing Si also indicated higher corrosion resistance.

Highly transparent, weakly hydrophilic and biodegradable cellulose film for flexible electroluminescent devices

Developing green substrates based on cellulose to substitute synthetic plastics meet the requirement for the sustainable future. However, cellulose-based substrates supporting for building electronic devices are usually opaque and highly hydrophilic, which ultimately limits the performance of optoelectronic devices. Herein, we report a new avenue for fabrication of highly transparent, weakly hydrophilic and biodegradable cellulose film. The acquired cellulose film not only has high transparency (over 90%), but also displays weak hydrophilicity (∼79° of initial water-contact angle) and still remains 3.5 MPa of tensile strength after soaking for two days in deionized water. Additionally, the degradation half-life of cellulose film is 20 days, and the cellulose films also have better thermostability. Moreover, the flexible electroluminescent devices have been successfully constructed by using this cellulose film as a green substrate. This novel strategy will greatly enrich the applications of cellulose films for next generation green electronics.

Effects of Polymethacrylamide‐Grafted Branch on Mechanical Performances, Hydrophilicity, and Biodegradability of Thermoplastic Starch Film

AbstractTo overcome the shortcomings of brittleness and high water uptake of thermoplastic native starch (TPNS) film, thermoplastic‐grafted starch (TPGS) film is prepared and tested using starch‐g‐polymethacrylamide (PMAM) with different percentages of grafting. Starch‐g‐PMAM is compounded in an internal mixer and then shaped by a compression molding machine to produce a TPGS film. Functional group analysis by Fourier transform infrared spectroscopy (FTIR) revealed that the graft copolymerization is successful, as evident from new characteristic infrared (IR) peaks of amide group (C═O stretching and N─H bending). TPGS films with MAM has more surface roughness than TPNS film does. With higher grafting percentages, the degrees of crystallinity and hydrophilicity of TPGS film reduce while the extensibility (based on strain at maximum load) and surface roughness increase, compared to that at lower percentages of grafting. The biodegradability of TPGS films grafted with MAM at different percentages is also examined.

Effect of pre-treatment temperatures on the film-forming properties of collagen fiber dispersions

Collagen fiber dispersions were formed and the influence of pre-treatment temperatures on the fiber structure and film-forming properties was investigated. A pre-transition at 33.0 °C and a main denaturation transition at around 42.8 °C were observed according to the dynamic temperature sweep of the dispersions. Accordingly, the dispersions were pre-treated at specific temperatures to obtain different structure of collagen fiber. The storage modulus and loss modulus of dispersions decreased sharply at > 39 °C. Also, the viscosity had a similar trend and the power law exponent n became larger. Microstructure and SDS-PAGE analysis showed that high temperature (≥45 °C) destroyed the fiber network and more low molecular weight fragments dissolved in dispersions. The tensile strength and elongation at break of films all decreased with the increase of temperature while the water solubility increased, attributing to the degeneration of collagen. The film hydrophilicity also increased due to more collagen turning into gelatin. However, the water vapor permeability and oxygen permeability of collagen fiber films were improved with the increase of temperature, indicating that suitable heating could improve their barrier properties. Moreover, the layered fiber network in films gradually disappeared with the increase of pre-treatment temperature. All films had typical characteristic infrared peaks of collagen and the values of AIII/A1450 gradually decreased from 1.2976 to 1.0802, indicating reduced contents of triple helix. The intensity of the XRD peaks at ~8° also decreased and higher temperatures promoted the stripping of collagen molecules from collagen fiber, where collagen molecular chains closely contact with each other.

Determining Water Sorption and Desorption in Thin Hydrophilic Polymer Films by Thermal Treatment

Knowledge of dry thickness of polymer films is required to determine the areal density of polymeric grafts and the degree of swelling of polymer networks and surface-anchored polymer assemblies. Because hydrophilic polymer films absorb water at ambient conditions and retain it, it is challenging to establish accurate dry thickness in such systems. Here we report on determining water uptake by chargeable/charged polymer films by monitoring the coefficient of thermal expansion (CTE) and thermo-optic coefficient (TOC) using ellipsometry. Knowing accurate amount of moisture in polymer films is needed for numerous applications, including, humidity and temperature sensors, polymer nanoreactors, lubricating coatings, antibacterial surfaces, and many others.

Optical and structural modifications of copper-fullerene nanocomposite thin films by 120 MeV Au ion irradiation

Swift heavy ion irradiation induced changes in metal-fullerene system have been investigated in this study. Cu–C70 nanocomposite thin films are irradiated with 120 MeV Au ions at different fluences and the corresponding modifications have been studied. The transformation of fullerene to amorphous carbon takes place at a fluence of 6 × 1012 ions cm−2 as demonstrated by Raman spectra. Atomic force microscopy results indicate the evolution of surface nanostructures with increasing fluence. The film irradiated at a fluence of 3 × 1012 ions cm−2 shows maximum surface roughness. Absorption spectra reveal that such a small concentration of copper is not sufficient to induce the phenomenon of surface plasmon resonance. Hydrophilicity of films has also undergone a dramatic change through various stages of ion bombardment. The possibility of removal of copper oxide (CuO) through ion irradiation has been shown by X-ray photoelectron spectroscopy results.

Hydrophobic surface modified HfO2 antireflective coatings

A multifunctional antireflective (AR) thin film is always a prerequisite for growing high-tech applications. Herein we proposed a surface modification technique to transform the hydrophilic behaviour of HfO2 AR nanofilms into hydrophobic without influencing the nanostructure, morphology, refractive index (η) or AR efficacy of HfO2 nanofilms. Our experimental results demonstrate that the fabricated HfO2 AR nanofilms retain its AR efficiency after surface modification to <1% in the visible wavelength range (450–700 nm) on FTO and sapphire. HfO2 AR nanofilms show hydrophilic behaviour before surface modification with a water contact angle (WCA) of 29° on FTO and 22° on sapphire. However, after surface treatment, they display hydrophobic nature θw > θ > 90° with a contact angle of (127°–130°). The experimental result demonstrates that the η of the thin layers fabricated at deposition angle 0°, 80°, and 88° before and after modification remains almost the same. HfO2 AR nanofilms exhibit long term AR permanency as AR efficiency measured within a year practically displays the equivalent reflectance curves similar to as deposit AR thin films, i.e. <1% in the wavelength range of 450–700 nm. We proposed a cost-effective procedure to make hydrophilic AR films to show non-wetting behaviour for its long-term exposure in a moist, damp environment without affecting the refractive index of AR thin film.

Corn and cassava starch with carboxymethyl cellulose films and its mechanical and hydrophobic properties

The amylose and amylopectin content of starch influences its functional characteristics and its interaction with other materials. Thus, it is important to study the mechanical strength and hydrophilicity of starch films of different botanical origins to elucidate the influence of their constituents in the interaction with carboxymethyl cellulose (CMC). The objective of this work was to evaluate the mechanical and physico-chemical properties of corn and cassava starch films and their blends with CMC by casting. The addition of CMC improved the tensile, increasing the strength at 206% for its blends with corn starch and 51% for its blends with cassava starch, the rupture stress at 89% and 74%, respectively, and the rupture strain at 381% and 57%, respectively. The elastic modulus presented increase of 20% for corn starch/CMC and 18% for cassava starch/CMC and the water vapor permeability at 48 and 40%, respectively. The corn starch film was more hydrophobic due to its higher amylose content, which contributed to the interaction between starch and glycerol OH groups and CMC COOH groups. This interaction was evidenced by FTIR and contact angle analysis, turning corn starch/CMC films into less hydrophilic material and reducing its water vapor permeability rate, which made this material promising for several applications, including food packaging.

Surface modification of PVA thin film by nonthermal atmospheric pressure plasma for antifogging property

In this work, a polyvinyl alcohol (PVA) thin film was modified by exposure to a dielectric barrier discharge argon plasma. The plasma was generated by a sinusoidal power supply with discharge voltage of 4.75 kV (rms), and frequency of 30 kHz at duty cycle 6.13%. The effect of the plasma on the PVA thin film was investigated by analyzing the contact angle, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and UV–visible spectroscopy. After the plasma treatment, the contact angle was found to be decrease from 29.6 ± 0.4° to 14.5 ± 0.2°, which implied that the surface property had changed to a hydrophilic state caused by an increase in the surface roughness and introduction of oxygen, including a polar carbonyl group. It was found that the plasma-treated hydrophilic PVA thin film exhibited excellent antifogging and highly transparent characteristics, making it an appropriate material for food packaging and green houses.