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20 pages, 6160 KiB

Open AccessArticle

Effect of Various Plasticizers in Different Concentrations on Physical, Thermal, Mechanical, and Structural Properties of Wheat Starch-Based Films

by Abdulrahman A. B. A. Mohammed, Zaimah Hasan, Abdoulhdi A. Borhana Omran, Abdulhafid M. Elfaghi, M.A. Khattak, R. A. Ilyas and S. M. Sapuan

Polymers 2023, 15(1), 63; https://doi.org/10.3390/polym15010063 - 23 Dec 2022

Cited by 14 | Viewed by 3310

Abstract

Biocomposite materials are essential for environmental protection, as they have the ability of substituting synthetic plastic with natural materials. This work investigated how different plasticizers (Glycerol (G), Fructose (F), Sorbitol (S), and Urea (U)) affect the morphological, mechanical, thermal, and physical characteristics of [...] Read more.

Biocomposite materials are essential for environmental protection, as they have the ability of substituting synthetic plastic with natural materials. This work investigated how different plasticizers (Glycerol (G), Fructose (F), Sorbitol (S), and Urea (U)) affect the morphological, mechanical, thermal, and physical characteristics of films made of wheat starch at various concentrations (0%, 15%, 25%, and 35%). Plasticizers were added to improve the flexibility and homogeneity of the wheat starch-based bioplastic. Control film exhibited high tensile strength (38.7 MPa) with low elongation (1.9%). However, films plasticized with 35% sorbitol showed the highest elongation, which was 60.7% at break. At 35% of all plasticizers, fructose showed the highest tensile strength, with 7.6 MPa. The addition of different plasticizers shows improvement in water resistance; films plasticized with glycerol had the lowest water absorption at 35% fructose (187.4%) and also showed coherent surfaces. Glycerol, sorbitol, and urea films showed a higher mass loss compared to fructose films. Fructose showed the highest performance after the analysis of the results, with low water absorption, water content, and mass loss and with high mechanical performance at 35% of fructose. SEM images show that the addition of fructose and glycerol improves the surface homogenate, while sorbitol and urea have a less compact structure with large pores. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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10 pages, 2052 KiB

Open AccessArticle

Dual Responsive Dependent Background Color Based on Thermochromic 1D Photonic Crystal Multilayer Films

by Yejin Kim, Seo Hyun Kim, Henok Getachew Girma, Seungju Jeon, Bogyu Lim and Seo-Hyun Jung

Polymers 2022, 14(23), 5330; https://doi.org/10.3390/polym14235330 - 06 Dec 2022

Cited by 2 | Viewed by 1745

Abstract

In this paper, we present dual responsive one-dimensional (1D) photonic crystal (PC) multilayer films that utilize a high-humidity environment and temperature. Dual responsive 1D PC multilayer films are fabricated on precoated thermochromic film by sequential alternate layer deposition of photo-crosslinkable poly(2-vinylnaphthalene-co-benzophenone acrylate) (P(2VN-co-BPA)) [...] Read more.

In this paper, we present dual responsive one-dimensional (1D) photonic crystal (PC) multilayer films that utilize a high-humidity environment and temperature. Dual responsive 1D PC multilayer films are fabricated on precoated thermochromic film by sequential alternate layer deposition of photo-crosslinkable poly(2-vinylnaphthalene-co-benzophenone acrylate) (P(2VN-co-BPA)) as a high refractive index polymer, and poly(4-vinylpyrollidone-co-benzophenone acrylate) P(4VP-co-BPA) as a low refractive index polymer. The thermochromic film shows a vivid color transition from black to white at 28 °C. Three different colors of thermochromic 1D PC multilayer films are prepared by thickness modulation of P(4VP-co-BPA) layers, and the films on a black background exhibit visible spectrum color only in a high-humidity environment (over 90% relative humidity (RH)). For the three films placed on a hands display, three different composite colors are synthesized by the reflection of light, including yellow, magenta, and cyan, due to the changing of backgrounds from black to white with temperature. Additionally, the films show remarkable color transitions with reliable reversibility. The films can be applied as anti-counterfeiting labels and can be used for smart decoration films. To the best of our knowledge, this is the first report of dual response colorimetric films that change color in various ways depending on temperature and humidity changes, and we believe that it can be applied to various applications. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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12 pages, 1832 KiB

Open AccessArticle

On the Properties of Nafion Membranes Recast from Dispersion in N-Methyl-2-Pyrrolidone

by Ekaterina Yu. Safronova, Daria Yu. Voropaeva, Anna A. Lysova, Oleg V. Korchagin, Vera A. Bogdanovskaya and Andrey B. Yaroslavtsev

Polymers 2022, 14(23), 5275; https://doi.org/10.3390/polym14235275 - 02 Dec 2022

Cited by 1 | Viewed by 1775

Abstract

Perfluorosulfonic acid Nafion membranes are widely used as an electrolyte in electrolysis processes and in fuel cells. Changing the preparation and pretreatment conditions of Nafion membranes allows for the optimization of their properties. In this work, a Nafion-NMP membrane with a higher conductivity [...] Read more.

Perfluorosulfonic acid Nafion membranes are widely used as an electrolyte in electrolysis processes and in fuel cells. Changing the preparation and pretreatment conditions of Nafion membranes allows for the optimization of their properties. In this work, a Nafion-NMP membrane with a higher conductivity than the commercial Nafion^® 212 membrane (11.5 and 8.7 mS∙cm⁻¹ in contact with water at t = 30 °C) and a comparable hydrogen permeability was obtained by casting from a Nafion dispersion in N-methyl-2-pyrrolidone. Since the ion-exchange capacity and the water uptake of these membranes are similar, it can be assumed that the increase in conductivity is the result of optimizing the Nafion-NMP microstructure by improving the connectivity of the pores and channels system. This leads to a 27% increase in the capacity of the membrane electrode assembly with the Nafion-NMP membrane compared to the Nafion^® 212 membrane. Thus, the method of obtaining a Nafion membrane has a great influence on its properties and performance of fuel cells based on them. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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14 pages, 6264 KiB

Open AccessArticle

Hydrophobic–Hydrophilic Properties and Characterization of PIM-1 Films Treated by Elemental Fluorine in Liquid Perfluorodecalin

by Nikolay A. Belov, Aleksandr Yu. Alentiev, Dmitrii S. Pashkevich, Fedor A. Voroshilov, Edgar S. Dvilis, Roman Yu. Nikiforov, Sergey V. Chirkov, Daria A. Syrtsova, Julia V. Kostina, Igor I. Ponomarev, Igor P. Asanov and Yulia G. Bogdanova

Polymers 2022, 14(23), 5152; https://doi.org/10.3390/polym14235152 - 26 Nov 2022

Cited by 4 | Viewed by 1783

Abstract

A direct fluorination technique was applied for the surface treatment of PIM-1 films in a liquid phase (perfluorodecalin). The fluorinated samples were analyzed by various instrumental techniques. ATR-IR spectroscopy showed that the fluorination predominantly takes place in methylene- and methyl-groups. Cyano-groups, aromatic hydrogens [...] Read more.

A direct fluorination technique was applied for the surface treatment of PIM-1 films in a liquid phase (perfluorodecalin). The fluorinated samples were analyzed by various instrumental techniques. ATR-IR spectroscopy showed that the fluorination predominantly takes place in methylene- and methyl-groups. Cyano-groups, aromatic hydrogens and the aromatic structure of the PIM-1 repeat unit were shown to be relatively stable at the fluorination conditions. XPS confirmed that the concentration of fluorine, as well as oxygen, in the near surface layer (~1 nm) increases with fluorination time. C1s and O1s surface spectra of the fluorinated PIM-1 samples indicated an appearance of newly-formed C-F and C-O functional groups. Scanning electron microscopy and X-ray energy-dispersive spectroscopy of the fluorinated PIM-1 samples showed an increase of the fluorine concentration at the surface (~0.1–1 μm) with the treatment duration. Analysis of the slices of the PIM-1 films demonstrated a decline of the fluorine content within several microns of the film depth. The decline increased with the fluorination time. A model of fluorine concentration dependence on the film depth and treatment duration was suggested. A change in the specific free surface energy as a result of PIM-1 fluorination was revealed. The fluorination time was shown to affect the surface energy (γ_SV), providing its shift from a low value (25 mJ∙m⁻²), corresponding to tetrafluoroethylene, up to a relatively high value, corresponding to a hydrophilic surface. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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17 pages, 3776 KiB

Open AccessArticle

Characterization of an In Vitro/Ex Vivo Mucoadhesiveness Measurement Method of PVA Films

by Laura Müller, Christoph Rosenbaum, Julius Krause and Werner Weitschies

Polymers 2022, 14(23), 5146; https://doi.org/10.3390/polym14235146 - 26 Nov 2022

Cited by 2 | Viewed by 1618

Abstract

Transmucosal drug delivery systems can be an attractive alternative to conventional oral dosage forms such as tablets. There are numerous in vitro methods to estimate the behavior of mucoadhesive dosage forms in vivo. In this work, a tensile test system was used to [...] Read more.

Transmucosal drug delivery systems can be an attractive alternative to conventional oral dosage forms such as tablets. There are numerous in vitro methods to estimate the behavior of mucoadhesive dosage forms in vivo. In this work, a tensile test system was used to measure the mucoadhesion of polyvinyl alcohol films. An in vitro screening of potential influencing variables was performed on biomimetic agar/mucin gels. Among the test device-specific factors, contact time and withdrawal speed were identified as influencing parameters. In addition, influencing factors such as the sample area, which showed a linear relationship in relation to the resulting work, and the liquid addition, which led to an abrupt decrease in adhesion, could be identified. The influence of tissue preparation was investigated in ex vivo experiments on porcine small intestinal tissue. It was found that lower values of F_max and W_ad were obtained on processed and fresh tissue than on processed and thawed tissue. Film adhesion on fresh, unprocessed tissue was lowest in most of the animals tested. Comparison of ex vivo measurements on porcine small intestinal tissue with in vitro measurements on agar/mucin gels illustrates the inter- and intra-individual variability of biological tissue. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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16 pages, 4137 KiB

Open AccessArticle

Multi-Shaded Edible Films Based on Gelatin and Starch for the Packaging Applications

by Iftikhar Ahmed Channa, Jaweria Ashfaq, Muhammad Ali Siddiqui, Ali Dad Chandio, Muhammad Ali Shar and Abdulaziz Alhazaa

Polymers 2022, 14(22), 5020; https://doi.org/10.3390/polym14225020 - 19 Nov 2022

Cited by 8 | Viewed by 3151

Abstract

Starch and gelatin are natural biopolymers that offer a variety of benefits and are available at relatively low costs. In addition to this, they are an appealing substitute for synthetic polymers for the manufacturing of packaging films. Such packaging films are not only [...] Read more.

Starch and gelatin are natural biopolymers that offer a variety of benefits and are available at relatively low costs. In addition to this, they are an appealing substitute for synthetic polymers for the manufacturing of packaging films. Such packaging films are not only biodegradable but are also edible. Moreover, they are environmentally friendly and remain extremely cost-effective. In lieu of this, films made from fish gelatin and cornstarch have been the subject of several experiments. The pristine gelatin films have poor performance against water diffusion but exhibit excellent flexibility. The goal of this study was to assess the performance of pristine gelatin films along with the addition of food plasticizers. For this purpose, solutions of gelatin/cornstarch were prepared and specified quantities of food colors/plasticizers were added to develop different shades. The films were produced by using a blade coating method and were characterized by means of their shaded colors, water vapor transmission rate (WVTR), compositional changes via Fourier transform infrared spectroscopy (FTIR), hardness, bendability, transparency, wettability, surface roughness, and thermal stability. It was observed that the addition of several food colors enhanced the moisture blocking effect, as a 10% reduction in WVTR was observed in the shaded films as compared to pristine films. The yellow-shaded films exhibited the lowest WVTR, i.e., around 73 g/m²·day when tested at 23 °C/65%RH. It was also observed that the films’ WVTR, moisture content, and thickness were altered when different colors were added into them, although the chemical structure remained unchanged. The mechanical properties of the shaded films were improved by a factor of two after the addition of colored plasticizers. Optical examination and AFM demonstrated that the generated films had no fractures and were homogeneous, clear, and shiny. Finally, a biscuit was packaged in the developed films and was monitored via shore hardness. It was observed that the edible packed sample’s hardness remained constant even after 5 days. This clearly suggested that the developed films have the potential to be used for packaging in various industries. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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23 pages, 4516 KiB

Open AccessArticle

Effect of Acetone as Co-Solvent on Fabrication of Polyacrylonitrile Ultrafiltration Membranes by Non-Solvent Induced Phase Separation

by Alexey Yushkin, Andrey Basko, Alexey Balynin, Mikhail Efimov, Tatyana Lebedeva, Anna Ilyasova, Konstantin Pochivalov and Alexey Volkov

Polymers 2022, 14(21), 4603; https://doi.org/10.3390/polym14214603 - 29 Oct 2022

Cited by 7 | Viewed by 2894

Abstract

For the first time, the presence of acetone in the casting solutions of polyacrylonitrile (PAN) in dimethylsulfoxide or N-methyl-2-pyrrolidone was studied with regards to thermodynamical aspects of phase separation of polymeric solutions induced by contact with non-solvent (water), formation and performance of porous [...] Read more.

For the first time, the presence of acetone in the casting solutions of polyacrylonitrile (PAN) in dimethylsulfoxide or N-methyl-2-pyrrolidone was studied with regards to thermodynamical aspects of phase separation of polymeric solutions induced by contact with non-solvent (water), formation and performance of porous membranes of ultrafiltration range. The positions of the liquid equilibrium binodals on the phase diagrams of these three-component and pseudo-three-component mixtures were determined. For PAN—N-methyl-2-pyrrolidone—water glass transition curve on a ternary phase diagram was plotted experimentally for the first time. The real-time evolution of the structure of mixtures of PAN with solvents (co-solvents) upon contact with a non-solvent (water) has been studied. The thermodynamic analysis of the phase diagrams of these mixtures, together with optical data, made it possible to propose a mechanism of structure formation during non-solvent induced phase separation of different mixtures. The addition of acetone promotes the formation of a spongy layer on the membrane surface, which decreases the probability of defect formation on the membrane surface and keeps finger-like macrovoids from the underlying layers of the membrane. It was shown that the molecular weight cut-off (MWCO) of the membranes can be improved from 58 down to 1.8 kg/mol by changing the acetone content, while polymer concentration remained the same. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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18 pages, 5368 KiB

Open AccessArticle

Chain-End Functionalization of Poly(ε-caprolactone) for Chemical Binding with Gelatin: Binary Electrospun Scaffolds with Improved Physico-Mechanical Characteristics and Cell Adhesive Properties

by Ilya Nifant’ev, Victoria Besprozvannykh, Andrey Shlyakhtin, Alexander Tavtorkin, Sergei Legkov, Maria Chinova, Irina Arutyunyan, Anna Soboleva, Timur Fatkhudinov and Pavel Ivchenko

Polymers 2022, 14(19), 4203; https://doi.org/10.3390/polym14194203 - 07 Oct 2022

Cited by 3 | Viewed by 1642

Abstract

Composite biocompatible scaffolds, obtained using the electrospinning (ES) technique, are highly promising for biomedical application thanks to their high surface area, porosity, adjustable fiber diameter, and permeability. However, the combination of synthetic biodegradable (such as poly(ε-caprolactone) PCL) and natural (such as gelatin Gt) [...] Read more.

Composite biocompatible scaffolds, obtained using the electrospinning (ES) technique, are highly promising for biomedical application thanks to their high surface area, porosity, adjustable fiber diameter, and permeability. However, the combination of synthetic biodegradable (such as poly(ε-caprolactone) PCL) and natural (such as gelatin Gt) polymers is complicated by the problem of low compatibility of the components. Previously, this problem was solved by PCL grafting and/or Gt cross-linking after ES molding. In the present study, composite fibrous scaffolds consisting of PCL and Gt were fabricated by the electrospinning (ES) method using non-functionalized PCL1 or NHS-functionalized PCL2 and hexafluoroisopropanol as a solvent. To provide covalent binding between PCL2 and Gt macromolecules, NHS-functionalized methyl glutarate was synthesized and studied in model reactions with components of spinning solution. It was found that selective formation of amide bonds, which provide complete covalent bonding of Gt in PCL/Gt composite, requires the presence of weak acid. With the use of the optimized ES method, fibrous mats with different PCL/Gt ratios were prepared. The sample morphology (SEM), hydrolytic resistance (FT-IR), cell adhesion and viability (MTT assay), cell penetration (fluorescent microscopy), and mechanical characteristics of the samples were studied. PCL2-based films with a Gt content of 20 wt% have demonstrated the best set of properties. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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12 pages, 4016 KiB

Open AccessArticle

Novel Transparent Films Composed of Bisphenol-A Polycarbonate and Copolyester

by Hiroyuki Hasegawa, Takumitsu Kida and Masayuki Yamaguchi

Polymers 2022, 14(19), 4146; https://doi.org/10.3390/polym14194146 - 03 Oct 2022

Cited by 3 | Viewed by 1621

Abstract

In this paper, the structure and properties of transparent films composed of bisphenol-A polycarbonate (PC) and a commercially available copolyester, poly(1,4-cyclohexanedimethanol-co-2,2,4,4-tetramethyl-1,3-cyclobutanediol-co-terephthalate) (CPE), were studied. Both PC and CPE films are known to be transparent with good mechanical toughness. It [...] Read more.

In this paper, the structure and properties of transparent films composed of bisphenol-A polycarbonate (PC) and a commercially available copolyester, poly(1,4-cyclohexanedimethanol-co-2,2,4,4-tetramethyl-1,3-cyclobutanediol-co-terephthalate) (CPE), were studied. Both PC and CPE films are known to be transparent with good mechanical toughness. It was found that PC/CPE (50/50) showed miscibility in both the molten and solid states, indicating that there is a high possibility for the blend system to be miscible in the whole blend ratios. Because of the miscibility, the blend films showed no light scattering originating from phase separation. The mechanical properties of the films, such as Young’s modulus, yield stress, and strain at break, were determined by the blend ratio, and the glass transition temperature increased with the PC content, which corresponded well with the values predicted by the Fox equation. These results demonstrate that the thermal and mechanical properties of the films can only be controlled by the blend ratio. Since these transparent films showed excellent mechanical toughness irrespective of the blend ratios, they can be employed in various applications. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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16 pages, 5005 KiB

Open AccessArticle

Spectroscopic Studies of Styrylquinoline Copolymers with Different Substituents

by Malgorzata Sypniewska, Anna Kaczmarek-Kędziera, Alexandra Apostoluk, Vitaliy Smokal, Anastasiia Krupka, Robert Szczesny and Beata Derkowska-Zielinska

Polymers 2022, 14(19), 4040; https://doi.org/10.3390/polym14194040 - 27 Sep 2022

Cited by 1 | Viewed by 1279

Abstract

The aim of the study was to present the influence of various styrylquinoline (StQ) substituents on the luminescence, structural, and optical properties of StQ-containing copolymers. StQ-containing copolymers were synthesized by free-radical thermoinitiated polymerization. The calculations of the copolymerization ratios for the obtained copolymers [...] Read more.

The aim of the study was to present the influence of various styrylquinoline (StQ) substituents on the luminescence, structural, and optical properties of StQ-containing copolymers. StQ-containing copolymers were synthesized by free-radical thermoinitiated polymerization. The calculations of the copolymerization ratios for the obtained copolymers were based on the basis of the integrated peak areas of the ¹H NMR spectra in CDCl₃. The luminescence measurements show that the change in the nature of the electron-donating and electron-withdrawing of the substituent shifts the emission band to longer wavelengths and causes a transition from blue fluorescence to green or yellow and orange (or even white), regardless of the electronic nature of the introduced substituent group. The structural properties were measured by Fourier-Transform Infrared (FTIR) and Raman spectroscopies. For all of the compounds, we observed similarities in the bands in FTIR and Raman measurements. The optical parameters were obtained from the absorbance measurements. Additionally, Scanning Electron Microscopy (SEM) was used to study the surface topography of the thin layers on the glass substrate. The SEM images confirm that we obtained smoother layers for two copolymers. The computational Density Functional Theory (DFT) analysis fully supports the beneficial features of the analyzed systems for their applications in optoelectronic devices. Based on the obtained results, it can be concluded that all of the studied styrylquinolines are promising materials for applications in organic light-emitting diodes (OLEDs). However, COP1 with an OCH₃ donor substituent possess a wider luminescence band, and its layer is smoother and more transparent. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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19 pages, 7155 KiB

Open AccessArticle

Mixed-Matrix Membranes Based on Polyetherimide, Metal–Organic Framework and Ionic Liquid: Influence of the Composition and Morphology on Gas Transport Properties

by Sarra Zid, Pierre Alcouffe, Matthieu Zinet and Eliane Espuche

Polymers 2022, 14(17), 3489; https://doi.org/10.3390/polym14173489 - 25 Aug 2022

Cited by 1 | Viewed by 1380

Abstract

In this work, membranes based on polyetherimide (PEI), a ZIF-8 metal–organic framework and 1-ethyl-methylimidazolium tetrafluoroborate ionic liquid (IL) were prepared. IL and ZIF-8 contents amounting to 7 wt% and 25 wt%, respectively, were investigated. CO₂, He and H₂ transport properties [...] Read more.

In this work, membranes based on polyetherimide (PEI), a ZIF-8 metal–organic framework and 1-ethyl-methylimidazolium tetrafluoroborate ionic liquid (IL) were prepared. IL and ZIF-8 contents amounting to 7 wt% and 25 wt%, respectively, were investigated. CO₂, He and H₂ transport properties of PEI/IL/ZIF-8 membranes were compared to those obtained for the respective PEI/ZIF-8 and PEI/IL systems. Membranes’ gas permeability and selectivity are discussed as a function of the membrane composition and morphology, and they were assessed in relation to existing experimental and theoretical data from the literature. Promising gas transport properties were obtained using the appropriate combination of ZIF-8 and IL amounts in the PEI matrix. Indeed, an increase in the CO₂ permeability coefficient by a factor of around 7.5 and the He and H₂ permeability coefficients by a factor of around 4 was achieved by adding 7 wt% IL and 10 wt% ZIF-8 to the PEI matrix. Moreover, diffusion was evidenced as a governing factor in the studied membrane series. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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20 pages, 5815 KiB

Open AccessArticle

Catalytic Etherification of ortho-Phosphoric Acid for the Synthesis of Polyurethane Ionomer Films

by Ilsiya M. Davletbaeva, Oleg O. Sazonov, Ilyas N. Zakirov, Ruslan S. Davletbaev, Sergey V. Efimov and Vladimir V. Klochkov

Polymers 2022, 14(16), 3295; https://doi.org/10.3390/polym14163295 - 12 Aug 2022

Viewed by 1606

Abstract

The etherification reaction of ortho-phosphoric acid (OPA) with polyoxypropylene glycol in the presence of tertiary amines was studied. The reaction conditions promoting the catalytic activity of triethanolamine (TEOA) and triethylamine (TEA) in the low-temperature etherification of OPA were established. The catalytic activity [...] Read more.

The etherification reaction of ortho-phosphoric acid (OPA) with polyoxypropylene glycol in the presence of tertiary amines was studied. The reaction conditions promoting the catalytic activity of triethanolamine (TEOA) and triethylamine (TEA) in the low-temperature etherification of OPA were established. The catalytic activity of TEOA and TEA in the etherification reaction of phosphoric acid is explained by the hydrophobic-hydrophilic interactions of TEA with PPG, leading, as a result of collective interactions, to a specific orientation of polyoxypropylene chains around the tertiary amine. When using triethylamine, complete etherification of OPA occurs, accompanied by the formation of branched OPA ethers terminated by hydroxyl groups and even the formation of polyphosphate structures. When triethanolamine is used as a catalyst, incomplete etherification of OPA with polyoxypropylene glycol occurs and as a result, part of the phosphate anions remain unreacted in the composition of the resulting aminoethers of ortho-phosphoric acid (AEPA). In this case, the hydroxyl groups of triethanolamine are completely involved in the OPA etherification reaction, but the catalytic activity of the tertiary amine weakens due to a decrease in its availability in the branched structure of AEPA. The kinetics of the etherification reaction of OPA by polyoxypropylene glycol catalyzed by TEOA and TEA were studied. It was shown that triethanolamine occupies a central position in the AEPA structure. The physico-mechanical and thermomechanical properties of polyurethane ionomer films obtained on the basis of AEPA synthesized in a wide temperature range were studied. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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13 pages, 2954 KiB

Open AccessArticle

On-the-Fly Formation of Polymer Film at Water Surface

by Veronica Vespini, Sara Coppola and Pietro Ferraro

Polymers 2022, 14(15), 3228; https://doi.org/10.3390/polym14153228 - 08 Aug 2022

Cited by 2 | Viewed by 1946

Abstract

The self-propulsion of bodies floating in water is of great interest for developing new robotic and intelligent systems at different scales, and whenever possible, Marangoni propulsion is an attractive candidate for the locomotion of untethered micro-robots. Significant cases have been shown using liquid [...] Read more.

The self-propulsion of bodies floating in water is of great interest for developing new robotic and intelligent systems at different scales, and whenever possible, Marangoni propulsion is an attractive candidate for the locomotion of untethered micro-robots. Significant cases have been shown using liquid and solid surfactants that allow an effective propulsion for bodies floating on water to be achieved. Here, we show for the first time a strategy for activating a twofold functionality where the self-propulsion of a floating body is combined with the formation of a polymer thin film at the water surface. In fact, we demonstrate that by using polymer droplets with an appropriate concentration of solvent and delivering such drops at specific locations onto freely floating objects, it is possible to form “on-the-fly” thin polymer films at the free water surface. By exploiting self-propulsion, a polymer thin film can be formed that could cover quite extensive areas with different shapes depending on the motion of the floating object. This intriguing twice-functionality activated though a single phenomenon, i.e., film formation and related locomotion, could be used in perspective to perform complex operations at water surfaces, such as dynamic liquid packaging, cleaning, and moving away floating particles, monolayer films, or macro-sized objects, as discussed in the text. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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17 pages, 6108 KiB

Open AccessArticle

Molecular Compatibility and Hydrogen Bonding Mechanism of PES/PEI Blends

by Yuanlu Zhu, Weixing Wu, Ming Gao, Jiangyi Yan and Beifu Wang

Polymers 2022, 14(15), 3046; https://doi.org/10.3390/polym14153046 - 27 Jul 2022

Cited by 6 | Viewed by 2123

Abstract

The development of high-performance polymer membranes has sparked a lot of attention in recent years. Polymer blending is a potential method of modification. A limitation, however, is the compatibility of blends at the molecular level. In this investigation, polyethersulfone/polyetherimide hollow fiber membranes were [...] Read more.

The development of high-performance polymer membranes has sparked a lot of attention in recent years. Polymer blending is a potential method of modification. A limitation, however, is the compatibility of blends at the molecular level. In this investigation, polyethersulfone/polyetherimide hollow fiber membranes were prepared by the solution blending method. Compatibility, hydrogen bonding, crystallinity, microstructure, hydrophilicity, mechanical properties, and transmissibility of blended membranes were also characterized. The compatibility and hydrogen bonding action of the two components were confirmed by DSC, FTIR, XPS, and XRD. The structure exhibits a C−H···O interaction motif with the sulfone group acting as a hydrogen bond acceptor from a methyl C−H donor. The π–π stacking between the two polymers arranged molecules more orderly, resulting in enhanced intermolecular interactions. Compared to polyethersulfone hollow fiber membranes, the hydrophilic, mechanical properties, and rejection rate of the blended membranes are more effectively enhanced. Self-assembly of the host polymer with a polymer capable of forming hydrogen bonds to construct controllable blends is a crucial and proven method. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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14 pages, 4264 KiB

Open AccessArticle

Photothermal Thin Films with Highly Efficient NIR Conversion for Miniaturized Liquid-Crystal Elastomer Actuators

by Wei-Yi Wang, Bo-You Lin, Yen-Peng Liao and Yao-Joe Yang

Polymers 2022, 14(15), 2997; https://doi.org/10.3390/polym14152997 - 24 Jul 2022

Cited by 3 | Viewed by 2175

Abstract

This work presents the development of highly efficient photothermal thin films (PTFs) and the demonstration of their application on miniaturized polymer-based soft actuators. The proposed PTF, which comprises acrylic-based black paint and EGaIn liquid metal (LM) microdroplets, serves as an excellent absorber for [...] Read more.

This work presents the development of highly efficient photothermal thin films (PTFs) and the demonstration of their application on miniaturized polymer-based soft actuators. The proposed PTF, which comprises acrylic-based black paint and EGaIn liquid metal (LM) microdroplets, serves as an excellent absorber for efficiently converting near-infrared (NIR) irradiation into heat for actuating liquid-crystal elastomer (LCE) actuators. The introduction of LM microdroplets into the PTFs effectively increases the overall thermal efficiency of PTFs. Miniaturized soft crawlers monolithically integrated with the NIR-driven LCE actuators are also implemented for demonstrating the application of the proposed PTF. The crawler’s locomotion, which is inspired by the rectilinear movement of snakes, is generated with the proposed PTF for inducing the LC-to-isotropic phase transition of the LCEs. The experimental results show that introducing LM microdroplets into the PTF can effectively reduce the thermal time constants of LCE actuators by 70%. Under periodic on/off NIR illumination cycles, the locomotion of crawlers with different dimensions is also demonstrated. The measurement results indicate that the proposed PTF is not only essential for enabling photothermal LCE actuation but also quite efficient and durable for repeated operation. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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11 pages, 778 KiB

Open AccessArticle

Comparative Study of Polyethylene Films Embedded with Oxide Nanoparticles of Granulated and Free-Standing Nature

by Stavros Christopoulos, Nicos C. Angastiniotis, Valerie Laux - Le Guyon, Eliane Bsaibess, Loukas Koutsokeras, Benoît Duponchel, Joumana El-Rifai, Liang Li and Ahmed Slimani

Polymers 2022, 14(13), 2629; https://doi.org/10.3390/polym14132629 - 28 Jun 2022

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Abstract

Nanocomposite polymer films are a very diverse research field due to their many applications. The search for low-cost, versatile methods, producing regulated properties of the final products, has thus become extremely relevant. We have previously reported a bulk-scale process, dispersing granulated metal oxide [...] Read more.

Nanocomposite polymer films are a very diverse research field due to their many applications. The search for low-cost, versatile methods, producing regulated properties of the final products, has thus become extremely relevant. We have previously reported a bulk-scale process, dispersing granulated metal oxide nanoparticles, of both unary and multi-component nature, in a low-density polyethylene (LDPE) polymer matrix, establishing a reference in the produced films’ optical properties, due to the high degree of homogeneity and preservation of the primary particle size allowed by this method. In this work, unmodified, free-standing particles, namely zinc oxide (

Z n O

), titanium dioxide (

T i O_{2}

), aluminum oxide (

A l_{2} O_{3}

), and silicon dioxide (

S i O_{2}

) are blended directly with LDPE, and the optical properties of the fabricated films are compared to those of films made using the granulation process. The direct blending process evidently allows for control of the secondary particle size and ensures a homogeneous dispersion of the particles, albeit to a lesser extent than the granulation process. Despite the secondary particle size being comparatively larger than its granulated counterpart, the process still provides a regulated degree of deagglomeration of the free-standing oxide particles, so it can be used as a low-cost alternative. The regulation of the secondary particle size tunes the transmission and reflection spectra, in both unary and mixed oxide compositions. Finally, the direct blending process exhibits a clear ability to tune the energy band gap in mixed oxides. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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23 pages, 6778 KiB

Open AccessArticle

Novel Mixed Matrix Membranes Based on Polyphenylene Oxide Modified with Graphene Oxide for Enhanced Pervaporation Dehydration of Ethylene Glycol

by Mariia Dmitrenko, Anastasia Chepeleva, Vladislav Liamin, Anton Mazur, Konstantin Semenov, Nikolay Solovyev and Anastasia Penkova

Polymers 2022, 14(4), 691; https://doi.org/10.3390/polym14040691 - 11 Feb 2022

Cited by 16 | Viewed by 2417

Abstract

Ethylene glycol (EG) is widely used in various economic and industrial fields. The demand for its efficient separation and recovery from water is constantly growing. To improve the pervaporation characteristics of a poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) membrane in dehydration of ethylene glycol, the modification [...] Read more.

Ethylene glycol (EG) is widely used in various economic and industrial fields. The demand for its efficient separation and recovery from water is constantly growing. To improve the pervaporation characteristics of a poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) membrane in dehydration of ethylene glycol, the modification with graphene oxide (GO) nanoparticles was used. The effects of the introduction of various GO quantities into the PPO matrix on the structure and physicochemical properties were studied by Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies, scanning electron (SEM) and atomic force (AFM) microscopies, thermogravimetric analysis (TGA), swelling experiments, and contact angle measurements. Two types of membranes based on PPO and PPO/GO composite were developed: dense membranes and supported membranes on a fluoroplast substrate (MFFC). Transport properties of the developed membranes were evaluated in the pervaporation dehydration of EG in a wide concentration range (10–90 wt.% and 10–30 wt.% water for the dense and supported membranes, respectively). The supported PPO/GO(0.7%)/MFFC membrane demonstrated the best transport properties in pervaporation dehydration of EG (10–30 wt.% water) at 22 °C: permeation flux ca. 15 times higher compared to dense PPO membrane—180–230 g/(m²·h)), 99.8–99.6 wt.% water in the permeate. The membrane is suitable for the promising industrial application. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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Review

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25 pages, 3163 KiB

Open AccessReview

A Review on the Development of an Integer System Coupling Forward Osmosis Membrane and Ultrasound Waves for Water Desalination Processes

by Bara A. K. Al-Sakaji, Sameer Al-Asheh and Munjed A. Maraqa

Polymers 2022, 14(13), 2710; https://doi.org/10.3390/polym14132710 - 01 Jul 2022

Cited by 2 | Viewed by 1985

Abstract

This review considers the forward osmosis (FO) membrane process as one of the feasible solutions for water desalination. Different aspects related to the FO process are reviewed with an emphasis on ultrasound assisted FO membrane processes. The different types of membranes used in [...] Read more.

This review considers the forward osmosis (FO) membrane process as one of the feasible solutions for water desalination. Different aspects related to the FO process are reviewed with an emphasis on ultrasound assisted FO membrane processes. The different types of membranes used in FO are also reviewed and discussed; thus, their configuration, structure and applications are considered. Coupling ultrasound with FO enhances water flux through the membrane under certain conditions. In addition, this review addresses questions related to implementation of an ultrasound/FO system for seawater desalination, such as the impact on fouling, flow configuration, and location of fouling. Finally, the mechanisms for the impact of ultrasound on FO membranes are discussed and future research directions are suggested. Full article

(This article belongs to the Special Issue Feature Papers in Polymer Membranes and Films)

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