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Volume 15
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Polymers, Volume 15, Issue 2 (January-2 2023) – 223 articles

Cover Story (view full-size image): Porous materials are attracting growing interest thanks to the many applications in multiple fields which include energy storage and conversion, drug delivery and tissue engineering. Polymers, in particular, have additional advantages as they are lightweight, do not contain heavy metals and are highly functionalizable. In this study, we use molecular dynamics simulations to characterize the structure and mechanical response, spanning elastic, plastic and fracture regimes, of a porous polymer material, obtained via glassy arrested phase separation. View this paper
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10 pages, 4529 KiB  
Article
Friction Behavior between Carbon Fiber Plain Weave and Metal Semi-Cylinder Tool
by Ning Wu, Qi Guo, Ximing Xie and Li Chen
Polymers 2023, 15(2), 472; https://doi.org/10.3390/polym15020472 - 16 Jan 2023
Cited by 1 | Viewed by 2259
Abstract
The deformations that occur during composite forming processes are governed by the friction between the fabrics and tooling material on the mesoscopic level. The effect of normal load and multi-plies on the frictional behavior of the carbon plain weave is investigated by simulating [...] Read more.
The deformations that occur during composite forming processes are governed by the friction between the fabrics and tooling material on the mesoscopic level. The effect of normal load and multi-plies on the frictional behavior of the carbon plain weave is investigated by simulating the friction between the fabric and metal semi-cylinder tool by using the experimental method. The periodic wavy friction-displacement curve between the metal tool and fabric is caused by the interwoven structure of the fabric. Both the increase in the normal load and the number of layers cause an increase in the real contact area during friction, leading to an increase in the friction force. The real contact area is calculated based on the Hertzian contact model and the self-designed testing method. The friction force values obtained from multiplying the real contact area with shear strength are closely aligned with the measured results. Full article
(This article belongs to the Special Issue Preparation and Performance Study of Polymer-Based Textile Composites)
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12 pages, 3083 KiB  
Article
Encapsulation of D-Limonene into O/W Nanoemulsions for Enhanced Stability
by Md Sohanur Rahman Sohan, Samar Elshamy, Grace Lara-Valderrama, Teetach Changwatchai, Kubra Khadizatul, Isao Kobayashi, Mitsutoshi Nakajima and Marcos A. Neves
Polymers 2023, 15(2), 471; https://doi.org/10.3390/polym15020471 - 16 Jan 2023
Cited by 5 | Viewed by 3190
Abstract
The present study aimed to investigate the physical stability in terms of (droplet size, pH, and ionic strength) and chemical stability in terms of (retention) of D-limonene (LM) in the nanoemulsions after emulsification as well as after storing them for 30 days under [...] Read more.
The present study aimed to investigate the physical stability in terms of (droplet size, pH, and ionic strength) and chemical stability in terms of (retention) of D-limonene (LM) in the nanoemulsions after emulsification as well as after storing them for 30 days under different temperatures (5 °C, 25 °C, and 50 °C). LM is a cyclic monoterpene and a major component extracted from citrus fruits. The modification of disperse phase with soybean oil (SB) and a nonionic emulsifier (Tween 80) was adequate to prepare stable LM-loaded nanoemulsions. LM blended with SB-loaded nanoemulsions were stable against droplet growth over pH (3–9) and ionic strength (0–500 mM NaCl). Regarding long-term storage, the prepared nanoemulsions demonstrated excellent physical stability with droplet size ranging from 120–130 nm during 30 days of storage at both 5 °C and 25 °C; however, oiling off started in the emulsions, which were stored at 50 °C from day 10. On the other hand, the retention of LM in the emulsions was significantly impacted by storage temperature. Nanoemulsions stored at 5 °C had the highest retention of 91%, while nanoemulsions stored at 25 °C had the lowest retention of 82%. Full article
(This article belongs to the Special Issue Function of Polymers in Encapsulation Process II)
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16 pages, 3282 KiB  
Article
Rheological Assessment of Oil-Xanthan Emulsions in Terms of Complex, Storage, and Loss Moduli
by Mamdouh Taha Ghannam, Mohamed Y. E. Selim, Abdulrazag Y. Zekri and Nabil Esmail
Polymers 2023, 15(2), 470; https://doi.org/10.3390/polym15020470 - 16 Jan 2023
Cited by 4 | Viewed by 1838
Abstract
This experimental assessment was carried out to study the viscoelastic performance of crude oil-xanthan emulsions employing a RheoStress RS100 rheometer. Crude oil with a concentration range of 0–75% by volume was used to prepare the oil-gum emulsions. Two xanthan gums of Sigma and [...] Read more.
This experimental assessment was carried out to study the viscoelastic performance of crude oil-xanthan emulsions employing a RheoStress RS100 rheometer. Crude oil with a concentration range of 0–75% by volume was used to prepare the oil-gum emulsions. Two xanthan gums of Sigma and Kelzan were added in the emulsions with concentration ranges of 0–104 ppm. The linear viscoelastic ranges of all the tested oil-gum emulsions were found in the range of 0.1–10 Pa. Thus, the experimental tests were completed within the linear viscoelastic range of 1 Pa. The complex modulus increased gradually and steadily with frequency and gum concentration for all the examined emulsions. The addition of crude oil into the lighter xanthan concentration of <103 ppm provided almost the same behavior as the xanthan solution, whereas the presence of crude oil within the higher xanthan concentrations significantly stimulated the measured values of the complex modulus. For lower gum concentrations of up to 1000 ppm, oil concentration displayed no effect on both the storage and loss moduli, whereas for gum concentrations higher than 1000 ppm, both moduli increased gradually with crude oil concentration. Full article
(This article belongs to the Special Issue Polymer Applications for Enhanced Oil Recovery: Challenges and Opportunities)
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16 pages, 2490 KiB  
Article
Extraction and Characterization of Fiber and Cellulose from Ethiopian Linseed Straw: Determination of Retting Period and Optimization of Multi-Step Alkaline Peroxide Process
by Kibrom Feleke, Ganesh Thothadri, Habtamu Beri Tufa, Ali A. Rajhi and Gulam Mohammed Sayeed Ahmed
Polymers 2023, 15(2), 469; https://doi.org/10.3390/polym15020469 - 16 Jan 2023
Cited by 23 | Viewed by 9287
Abstract
Flax is a commercial crop grown in many parts of the world both for its seeds and for its fibers. The seed-based flax variety (linseed) is considered less for its fiber after the seed is extracted. In this study, linseed straw was utilized [...] Read more.
Flax is a commercial crop grown in many parts of the world both for its seeds and for its fibers. The seed-based flax variety (linseed) is considered less for its fiber after the seed is extracted. In this study, linseed straw was utilized and processed to extract fiber and cellulose through optimization of retting time and a multi-step alkaline peroxide extraction process using the Taguchi design of experiment (DOE). Effects of retting duration on fiber properties as well as effects of solvent concentration, reaction temperature, and time on removal of non-cellulosic fiber components were studied using the gravimetric technique, Fourier transform infrared (FTIR) spectroscopy and thermal studies. Based on these findings, retting for 216 h at room temperature should offer adequate retting efficiency and fiber characteristics; 70% cellulose yield was extracted successfully from linseed straw fiber using 75% ethanol–toluene at 98 °C for 4 h, 6% NaOH at 75 °C for 30 min, and 6% H2O2 at 90 °C for 120 min. Full article
(This article belongs to the Special Issue Eco-Friendly Polymers: Synthesis, Characterization and Applications)
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17 pages, 3326 KiB  
Article
In Vitro Biocompatibility of Hydrogel Polyvinyl Alcohol/Moringa oleifera Leaf Extract/Graphene Oxide for Wound Dressing
by Dwi Ratna Ningrum, Wildan Hanif, Deby Fajar Mardhian and Lia A. T. W. Asri
Polymers 2023, 15(2), 468; https://doi.org/10.3390/polym15020468 - 16 Jan 2023
Cited by 24 | Viewed by 4291
Abstract
Hydrogel-based wound dressings are often chosen for healing diabetic foot ulcers (DFU) in combination with herbal extracts. Moringa oleifera leaf (MOL) extract is a potent herb containing antimicrobial and anti-inflammatory bioactive substances. In this work, wound dressings based on polyvinyl alcohol (PVA), MOL [...] Read more.
Hydrogel-based wound dressings are often chosen for healing diabetic foot ulcers (DFU) in combination with herbal extracts. Moringa oleifera leaf (MOL) extract is a potent herb containing antimicrobial and anti-inflammatory bioactive substances. In this work, wound dressings based on polyvinyl alcohol (PVA), MOL extract, and graphene oxide (GO) were developed for DFU wound dressing. The PVA/MOL/GO hydrogel was synthesized using four cycles of a freeze–thaw process with varying concentrations of MOL extract. All hydrogels showed a water content of 83–88% and an equilibrium swelling ratio between 155–171%. After degradation in phosphate-buffered saline, the hydrogels showed a more open porous structure. We observed a degradation rate of 26–28%. Although the increase in MOL extract reduced the tensile strength of the hydrogel, the addition of GO increased the tensile strength. The PVA/MOL/GO hydrogel showed the highest antibacterial activity, with a reduction of 94% Gram-positive S. aureus and 82% Gram-negative E. coli. Finally, all samples possessed appropriate cytocompatibility with cell viability reaching 83–135% in 3T3L1 mouse fibroblast cells. This result was verified by in vitro wound-healing analysis performed by scratch assay. This study presents the potency of combined PVA, MOL, and GO as a biocompatible DFU wound dressing. Full article
(This article belongs to the Section Smart and Functional Polymers)
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12 pages, 4531 KiB  
Article
Extraction of Keratin from Pig Nails and Electrospinning of Keratin/Nylon6 Nanofibers for Copper (II) Adsorption
by Lanlan Wei, Di Wang, Zhiheng Liao, Zexuan Gong, Wenwen Zhao, Jinyan Gu, Yan Li and Jingjun Li
Polymers 2023, 15(2), 467; https://doi.org/10.3390/polym15020467 - 16 Jan 2023
Cited by 6 | Viewed by 2462
Abstract
In this study, keratins were extracted from pig nail waste via the reduction method for the first time, using L-cysteine as the reductant and urea as the lytic agent. Nylon6 and pig nail keratin were successfully combined via electrospinning to generate a series [...] Read more.
In this study, keratins were extracted from pig nail waste via the reduction method for the first time, using L-cysteine as the reductant and urea as the lytic agent. Nylon6 and pig nail keratin were successfully combined via electrospinning to generate a series of nylon6/pig nail keratin nanofibers with a variety of keratin concentrations (0% to 8%, w/w). From the results, it was found that the best concentration was 6% (w/w). The morphologies of the electrospun nanofibers were examined via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structural properties were characterized using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), and the thermal properties were described using thermo-gravimetric analysis (TGA). These results confirmed that the nanofibers were composed of both polymeric phases. Finally, copper (II) was used as a model ion, and the nanofiber membranes exhibited a strong adsorption affinity for metal ions in the water samples. This study provides an important foundation for the application of nanofiber membranes in metal adsorption. Full article
(This article belongs to the Special Issue Advanced Polymeric Fiber Materials: Electrospinning, Chemical Synthesis, and Molecular Self Assembly)
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8 pages, 2644 KiB  
Article
Polyzwitterion–SiO2 Double-Network Polymer Electrolyte with High Strength and High Ionic Conductivity
by Lei Zhang, Haiqi Gao, Lixiang Guan, Yuchao Li and Qian Wang
Polymers 2023, 15(2), 466; https://doi.org/10.3390/polym15020466 - 16 Jan 2023
Cited by 3 | Viewed by 1987
Abstract
The key to developing high-performance polymer electrolytes (PEs) is to achieve their high strength and high ionic conductivity, but this is still challenging. Herein, we designed a new double-network PE based on the nonhydrolytic sol–gel reaction of tetraethyl orthosilicate and in situ polymerization [...] Read more.
The key to developing high-performance polymer electrolytes (PEs) is to achieve their high strength and high ionic conductivity, but this is still challenging. Herein, we designed a new double-network PE based on the nonhydrolytic sol–gel reaction of tetraethyl orthosilicate and in situ polymerization of zwitterions. The as-prepared PE possesses high strength (0.75 Mpa) and high stretchability (560%) due to the efficient dissipation energy of the inorganic network and elastic characteristics of the polymer network. In addition, the highest ionic conductivity of the PE reaches 0.44 mS cm−1 at 30 °C owning to the construction of dynamic ion channels between the polyzwitterion segments and between the polyzwitterion segments and ionic liquids. Furthermore, the inorganic network can act as Lewis acid to adsorb trace impurities, resulting in a prepared electrolyte with a high electrochemical window over 5 V. The excellent interface compatibility of the as-prepared PE with a Li metal electrode is also confirmed. Our work provides new insights into the design and preparation of high-performance polymer-based electrolytes for solid-state energy storage devices. Full article
(This article belongs to the Special Issue Organic-Inorganic Hybrid Materials III)
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44 pages, 19950 KiB  
Review
Hybridization of Wide-Angle X-ray and Neutron Diffraction Techniques in the Crystal Structure Analyses of Synthetic Polymers
by Kohji Tashiro, Katsuhiro Kusaka, Hiroko Yamamoto, Takaaki Hosoya, Shuji Okada and Takashi Ohhara
Polymers 2023, 15(2), 465; https://doi.org/10.3390/polym15020465 - 16 Jan 2023
Cited by 2 | Viewed by 2751
Abstract
The development in the crystal structure analysis of synthetic polymers using the hybridized combination of wide-angle X-ray and neutron diffraction (WAXD and WAND, respectively) techniques has been reviewed with many case studies performed by the authors. At first, the technical development was reviewed, [...] Read more.
The development in the crystal structure analysis of synthetic polymers using the hybridized combination of wide-angle X-ray and neutron diffraction (WAXD and WAND, respectively) techniques has been reviewed with many case studies performed by the authors. At first, the technical development was reviewed, in which the usage of high-energy synchrotron X-ray source was emphasized for increasing the total number of the observable diffraction peaks, and several examples were introduced. Secondly, the usage of the WAND method was introduced, in which the successful extraction of hydrogen atomic positions was described. The third example is to show the importance for the hybrid combination of these two diffraction methods. The quantitative WAXD data analysis gave the crystal structures of at-poly(vinyl alcohol) (at-PVA) and at-PVA-iodine complex. However, the thus-proposed structure models were found not to reproduce the observed WAND data very much. The reason came from the remarkable difference in the atomic scattering powers of the constituting atomic species between WAXD and WAND phenomena. The introduction of statistical disorder solved this serious problem, which reproduced both of the observed WAXD and WAND data consistently. The more systematic combination of WAXD and WAND methods, or the so-called X-N method, was applied also to the quantitative evaluation of the bonded electron density distribution along the skeletal chains, where the results about polydiacetylene single crystals were presented as the first successful study. Finally, the application of WAND technique in the trace of structural changes induced under the application of external stress or temperature was described. The future perspective is described for the development of structural science of synthetic polymers on the basis of the combined WAXD/WAND techniques. Full article
(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Japan (2021,2022))
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17 pages, 763 KiB  
Review
Color Stability of Polymer-Based Composite CAD/CAM Blocks: A Systematic Review
by Gaetano Paolone, Mauro Mandurino, Francesca De Palma, Claudia Mazzitelli, Nicola Scotti, Lorenzo Breschi, Enrico Gherlone, Giuseppe Cantatore and Alessandro Vichi
Polymers 2023, 15(2), 464; https://doi.org/10.3390/polym15020464 - 16 Jan 2023
Cited by 38 | Viewed by 3769
Abstract
Background: This systematic review aims to evaluate the color stability of resin composite CAD/CAM blocks (CCB) when submitted to staining solutions. Methods: A systematic search was performed on different databases (Embase, Medline, Scopus, Web of Science). Search terms were: ‘polymer infiltrated’, ‘polymer-based’, ‘resin [...] Read more.
Background: This systematic review aims to evaluate the color stability of resin composite CAD/CAM blocks (CCB) when submitted to staining solutions. Methods: A systematic search was performed on different databases (Embase, Medline, Scopus, Web of Science). Search terms were: ‘polymer infiltrated’, ‘polymer-based’, ‘resin nanoceramic’, ‘resin ceramic’, ‘hybrid composite’, ‘hybrid ceramic’, ‘composite ceramic’, ‘resin infiltrated’, ‘CAD-CAM’, ‘CAD/CAM’, ‘color stability’, ‘staining’, ‘staining susceptibility’, ‘color change’, ‘color difference’. Inclusion criteria: in vitro articles published in the English language until 18 September 2022 without initial time restriction evaluating the color stability of CCB when submitted to staining solutions. Exclusion criteria: studies investigating color change induced by smoke or whitening treatments; studies not including a clinical evaluation of the results using the thresholds for color perceptibility and acceptability. Risk of bias assessment using the QUIN tool. Findings: Out of the 378 initially retrieved articles, 19 were included in this review. They investigated 17 different CCBs and different artificial staining by liquid protocols, including coffee, red wine, tea, and cola. CCBs exceeded clinical acceptability thresholds for color shift in 18 out of 19 studies, with a significantly higher color stability than conventional hybrid resin-based composites (RBCs), and a significantly lower color stability than ceramic materials. The identified differences in CCBs in color stability can be attributed to the material’s composition, but also to the heterogeneity of staining procedures. Interpretation and clinical implication: Clinicians should be aware that, although to a lower degree when compared to RBCs used in direct or indirect procedures, CCBs undergo color changes to a higher degree in comparison to ceramic materials. Full article
(This article belongs to the Special Issue Polymers Strategies in Dental Therapy)
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12 pages, 1837 KiB  
Article
Viscoplastic Modeling of Surface Relief Grating Growth on Isotropic and Preoriented Azopolymer Films
by Nina Tverdokhleb, Sarah Loebner, Bharti Yadav, Svetlana Santer and Marina Saphiannikova
Polymers 2023, 15(2), 463; https://doi.org/10.3390/polym15020463 - 16 Jan 2023
Cited by 5 | Viewed by 2195
Abstract
We report on solving of two intriguing issues concerning the inscription of surface relief gratings within azopolymer thin films under irradiation with SS, PP and RL interference patterns. For this, we utilize the orientation approach and viscoplastic modeling in combination with experimental results, [...] Read more.
We report on solving of two intriguing issues concerning the inscription of surface relief gratings within azopolymer thin films under irradiation with SS, PP and RL interference patterns. For this, we utilize the orientation approach and viscoplastic modeling in combination with experimental results, where the change in surface topography is acquired in situ during irradiation with modulated light. First, the initial orientation state of polymer backbones is proved to be responsible for the contradictory experimental reports on the efficiency of the SS interference pattern. Different orientation states can influence not only the phase of SS grating but also its height, which is experimentally confirmed by using special pretreatments. Second, the faster growth of gratings inscribed by the RL interference pattern is shown to be promoted by a weak photosoftening effect. Overall, the modeled results are in good agreement with the order of relative growth efficiency: RL–PP–SS. Full article
(This article belongs to the Special Issue Advances in Functional Polymer Films)
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10 pages, 4254 KiB  
Article
Development of Uniform Polydimethylsiloxane Arrays through Inkjet Printing
by Ning Tu, Jeffery C. C. Lo and S. W. Ricky Lee
Polymers 2023, 15(2), 462; https://doi.org/10.3390/polym15020462 - 16 Jan 2023
Cited by 3 | Viewed by 2102
Abstract
The inkjet printing method is a promising method to deposit polymer and functional nanoparticles at the microscale. It can be applied in the fabrication of multicolor polymer light emitting diodes (polyLEDs), polymer base electronics, multicolor color conversion layers, and quantum dot light emitting [...] Read more.
The inkjet printing method is a promising method to deposit polymer and functional nanoparticles at the microscale. It can be applied in the fabrication of multicolor polymer light emitting diodes (polyLEDs), polymer base electronics, multicolor color conversion layers, and quantum dot light emitting diodes (QLEDs). One of the main challenges is to print high-resolution polymer dots from dilute polymer solution. In addition, the quality of printed multicolor polyLEDs, QLEDs and multicolor color conversion layers is currently limited by non-uniformity of the printed dots. In this paper, polydimethylsiloxane (PDMS) is selected as the functional polymer, due to its high transparency, good reflective index value, inflammable and flexible properties. The optimal ink to form a uniform PDMS dot array is presented in this paper. Both the solvent and PDMS were tuned to form the uniform PDMS dot array. The uniform PDMS dot array was printed with a diameter of around 50 µm, and the array of closely spaced green quantum dots (QDs) mixed with PDMS ink was also printed on the substrate uniformly. While the green QD-PDMS film was printed at a resolution of 1693 dpi, the uniformity was evaluated using the photoluminescence (PL) spectrum and color coordinate value. Full article
(This article belongs to the Special Issue Recent Development of Polymer Additives)
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14 pages, 1662 KiB  
Article
Simultaneous Treatment of Both Sides of the Polymer with a Conical-Shaped Atmospheric Pressure Plasma Jet
by Felipe Vicente de Paula Kodaira, Bruno Henrique Silva Leal, Thayna Fernandes Tavares, Antje Quade, Luis Rogerio de Oliveira Hein, William Chiappim and Konstantin Georgiev Kostov
Polymers 2023, 15(2), 461; https://doi.org/10.3390/polym15020461 - 16 Jan 2023
Cited by 3 | Viewed by 2152
Abstract
A conical-shaped atmospheric pressure plasma jet (CS-APPJ) was developed to overcome a standard limitation of APPJs, which is their small treatment area. The CS-APPJs increase the treatment area but use the same gas flow. In the present work, polypropylene samples were treated by [...] Read more.
A conical-shaped atmospheric pressure plasma jet (CS-APPJ) was developed to overcome a standard limitation of APPJs, which is their small treatment area. The CS-APPJs increase the treatment area but use the same gas flow. In the present work, polypropylene samples were treated by CS-APPJ and characterized by scanning electron microscope (SEM), the contact angle, Fourier-transformed infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). It was observed that the treatment co-occurs on the face directly in contact with the plasma and on the opposite face (OF) of the samples, i.e., no contact. However, the treatment changed the chemical composition on each side; the OF is rougher than the direct contact face (DCF), probably due to the oxygen groups in excess at the DCF and nitrogen in quantity at the OF. Although simultaneous treatment of both sides of the sample occurs for most atmospheric plasma treatments, this phenomenon is not explored in the literature. Full article
(This article belongs to the Special Issue Advances in Plasma Processes for Polymers II)
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12 pages, 12188 KiB  
Article
Efficacy of Denture Cleansers on Microbial Adherence and Surface Topography of Conventional and CAD/CAM-Processed Denture Base Resins
by Afnan F. Alfouzan, Malath Tuwaym, Ebtihal N. Aldaghri, Tagreed Alojaymi, Hadeel Minife Alotiabi, Sara M. Al Taweel, Hanan N. Al-Otaibi, Rizwan Ali, Huda Alshehri and Nawaf Labban
Polymers 2023, 15(2), 460; https://doi.org/10.3390/polym15020460 - 15 Jan 2023
Cited by 19 | Viewed by 3062
Abstract
This study assessed the efficacy of five denture cleansers on the microbial adherence and surface topography of conventional and CAD/CAM denture base resins. Acrylic resin discs were fabricated using conventional, milling, and 3D printing methods (N = 180). The discs were contaminated with [...] Read more.
This study assessed the efficacy of five denture cleansers on the microbial adherence and surface topography of conventional and CAD/CAM denture base resins. Acrylic resin discs were fabricated using conventional, milling, and 3D printing methods (N = 180). The discs were contaminated with dual species of Candida albicans and Streptococcus mutans biofilm for 72 h and then disinfected with either of the denture cleansers (Fittydent cleansing tablets, 2% Chlorhexidine gluconate, 0.2% Chlorhexidine gluconate, 0.5% sodium hypochlorite, and 1% sodium hypochlorite (n = 10). Distilled water served as the control group. The colony-forming units of the microorganisms were calculated, followed by post-treatment surface roughness. Data were statistically analyzed using one-way ANOVA, paired t-test, and post hoc Tukey HSD test (α = 0.05). Among the denture cleansers, 2% Chlorhexidine gluconate, 0.5% sodium hypochlorite, and 1% sodium hypochlorite had the best cleansing effect on the resin discs and demonstrated zero growth of colonies for both the species. Comparing the material groups, the 3D-processed discs showed higher colony-forming units followed by the conventional and CAD/CAM milled group. The highest surface roughness was demonstrated by the 3D-printed discs (0.690 ± 0.08 μm), followed by the conventional (0.493 ± 0.11 μm) and the milled groups (0.301 ± 0.08 μm). The tested chemical denture cleansers affected the Candida albicans and Streptococcus mutans adhesion compared to control discs immersed in distilled water. The clinician may recommend to their patient to use 2% chlorhexidine gluconate for the disinfection of CAD/CAM PMMA denture base materials. Full article
(This article belongs to the Section Polymer Processing and Engineering)
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15 pages, 4028 KiB  
Article
Preparation and Boron Removal Performance of Glycidol Modified PANI Nanorods: An Optimization Study Based on Response Surface Methodology
by Yunlong Le, Yunshan Guan, Xiaoying Ma and Weidong Zhang
Polymers 2023, 15(2), 459; https://doi.org/10.3390/polym15020459 - 15 Jan 2023
Cited by 3 | Viewed by 1576
Abstract
Boron removal from aqueous solutions has attracted increasing attention, offering benefits for animal and plant health as well as profound significance for exploiting Salt Lake boron resources. In this work, we synthesized novel glycidol-functionalized and hydrophilic polyaniline (PANI) nanorod adsorbents, which were prepared [...] Read more.
Boron removal from aqueous solutions has attracted increasing attention, offering benefits for animal and plant health as well as profound significance for exploiting Salt Lake boron resources. In this work, we synthesized novel glycidol-functionalized and hydrophilic polyaniline (PANI) nanorod adsorbents, which were prepared to separate boron compounds from boric acid aqueous solutions. The as-prepared adsorbents were significantly different from the traditional polymers’ grafting reaction because they had a higher functional yield and more active position for adsorption. The maximum adsorption capacity (0.2210 mmoL∙g−1) and optimal adsorption conditions (boric acid concentration of 1307 mg/L, pH = 9.82, time of 10 h) were obtained with single-factor experimentation and the response surface method (RSM). In addition, adsorption kinetics studies showed that the adsorption reaction belonged to the pseudo-first-order kinetic model, and diffusion was the key limiting factor; therefore, the adsorption equilibrium time is more than 10 h. Finally, the related possible adsorption mechanism was investigated based on the species and the diffusion of boron in the aqueous phase. Full article
(This article belongs to the Special Issue Development of Functional Polymer Composites)
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17 pages, 7330 KiB  
Article
Biocompatible Silica-Polyethylene Glycol-Based Composites for Immobilization of Microbial Cells by Sol-Gel Synthesis
by Daria G. Lavrova, Anton N. Zvonarev, Valery A. Alferov, Tat’yana G. Khonina, Elena V. Shadrina, Sergey V. Alferov and Olga N. Ponamoreva
Polymers 2023, 15(2), 458; https://doi.org/10.3390/polym15020458 - 15 Jan 2023
Cited by 8 | Viewed by 2945
Abstract
Biocatalysts based on the methylotrophic yeast Ogataea polymorpha VKM Y-2559 immobilized in polymer-based nanocomposites for the treatment of methanol-containing wastewater were developed. The organosilica composites with different matrix-to-filler ratios derived from TEOS/MTES in the presence of PEG (SPEG-composite) and from silicon-polyethylene [...] Read more.
Biocatalysts based on the methylotrophic yeast Ogataea polymorpha VKM Y-2559 immobilized in polymer-based nanocomposites for the treatment of methanol-containing wastewater were developed. The organosilica composites with different matrix-to-filler ratios derived from TEOS/MTES in the presence of PEG (SPEG-composite) and from silicon-polyethylene glycol (STPEG-composite) differ in the structure of the silicate phase and its distribution in the composite matrix. Methods of fluorescent and scanning microscopy first confirmed the formation of an organosilica shell around living yeast cells during sol-gel bio-STPEG-composite synthesis. Biosensors based on the yeast cells immobilized in STPEG- and SPEG-composites are characterized by effective operation: the coefficient of sensitivity is 0.85 ± 0.07 mgO2 × min−1 × mmol−1 and 0.87 ± 0.05 mgO2 × min−1 × mmol−1, and the long-term stability is 10 and 15 days, respectively. The encapsulated microbial cells are protected from UV radiation and the toxic action of heavy metal ions. Biofilters based on the developed biocatalysts are characterized by high effectiveness in the utilization of methanol-rich wastewater—their oxidative power reached 900 gO2/(m3 × cycle), and their purification degree was up to 60%. Full article
(This article belongs to the Special Issue Synthesis and Applications of Polymer-Based Nanocomposites)
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12 pages, 2829 KiB  
Article
Web Wrinkle Defects due to Temperature Profile in Roll-to-Roll Manufacturing Systems
by Jaehyun Noh, Minho Jo, Hojin Jeon, Minjae Kim, Jeongdai Jo and Changwoo Lee
Polymers 2023, 15(2), 457; https://doi.org/10.3390/polym15020457 - 15 Jan 2023
Cited by 5 | Viewed by 3761
Abstract
The roll-to-roll manufacturing system is extensively used for mass producing products made of plastic, paper, and fabric in several traditional industries. When flexible substrates, also known as webs, are heated and transported inside the dryer, an inconsistent temperature distribution occurs on the material [...] Read more.
The roll-to-roll manufacturing system is extensively used for mass producing products made of plastic, paper, and fabric in several traditional industries. When flexible substrates, also known as webs, are heated and transported inside the dryer, an inconsistent temperature distribution occurs on the material in the machine direction (MD) and cross-machine direction (CMD). If rollers are not aligned in parallel on the same plane in the roll-to-roll web handling process, or if roller misalignment exists, strain deviation occurs in the web, resulting in lateral displacement and web wrinkles. Therefore, this study examined a wrinkle, which is a thermal deformation that occurs when an inconsistent web temperature distribution is formed on the material inside a dryer. The changes in the elastic modulus and thermal expansion of the web were also examined. Experiments were conducted using a PET film, and its elastic modulus and thermal expansion were examined. The results showed that the presence of a web wrinkle defect can cause a thickness deviation in the functional layer manufactured on the web. Moreover, an appropriate operating speed should be set to reduce the CMD temperature deviation, thereby reducing instances of wrinkle defects. Full article
(This article belongs to the Special Issue Theoretical Calculation and Simulation of Polymer)
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20 pages, 11042 KiB  
Article
Experimental Investigation on the Low-Velocity Impact Response of Tandem Nomex Honeycomb Sandwich Panels
by Jinbo Fan, Penghui Li, Weiqi Guo, Xiuguo Zhao, Chen Su and Xinxi Xu
Polymers 2023, 15(2), 456; https://doi.org/10.3390/polym15020456 - 15 Jan 2023
Cited by 13 | Viewed by 2706
Abstract
Sandwich panels are often subjected to unpredictable impacts and crashes in applications. The core type and impactor shape affect their impact response. This paper investigates the responses of five tandem Nomex honeycomb sandwich panels with different core-types under low-velocity-impact conditions with flat and [...] Read more.
Sandwich panels are often subjected to unpredictable impacts and crashes in applications. The core type and impactor shape affect their impact response. This paper investigates the responses of five tandem Nomex honeycomb sandwich panels with different core-types under low-velocity-impact conditions with flat and hemispherical impactors. From the force response and impact displacement, gradient-tandem and foam-filled structures can improve the impact resistance of sandwich panels. Compared with the single-layer sandwich panel, the first peak of contact force of the foam-gradient-filled tandem honeycomb sandwich panels increased by 34.84%, and maximum impact displacement reduced by 50.98%. The resistance of gradient-tandem Nomex honeycomb sandwich panels under low-velocity impact outperformed uniform-tandem structures. Foam-filled structures change the impact responses of the tandem sandwich panels. Impact damage with a flat impactor was more severe than the hemispherical impactor. The experimental results are helpful in the design of tandem Nomex honeycomb sandwich panels. Full article
(This article belongs to the Special Issue Dynamic Behavior of Polymer Composite Materials and Structures)
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16 pages, 1226 KiB  
Article
Synthesis and Characterization of Functional Cellulose–Ether-Based PCL- and PLA-Grafts-Copolymers
by Korbinian Sommer, Daniel Van Opdenbosch and Cordt Zollfrank
Polymers 2023, 15(2), 455; https://doi.org/10.3390/polym15020455 - 15 Jan 2023
Cited by 2 | Viewed by 2078
Abstract
The use of biodegradable materials such as cellulose and polyesters can be extended through the combination, as well as modification, of these biopolymers. By controlling the molecular structure and composition of copolymers of these components, it should also be possible to tailor their [...] Read more.
The use of biodegradable materials such as cellulose and polyesters can be extended through the combination, as well as modification, of these biopolymers. By controlling the molecular structure and composition of copolymers of these components, it should also be possible to tailor their material properties. We hereby report on the synthesis and characterization of cellulose-based graft copolymers with a precise molecular composition and copolymer architecture. To prepare such materials, we initially modified cellulose through the regioselective protection of the 6-OH group using trityl chloride. The 6-O protected compound was then alkylated, and deprotection at the 6-OH group provided the desired 2,3-di-O-alkyl cellulose compounds that were used as macroinitiators for ring opening polymerization. Regioselective modification was hereby necessary to obtain compounds with an exact molecular composition. Ring opening polymerization, catalyzed by Sn(Oct)2, at the primary 6-OH group of the cellulose macroinitiator, using L-lactide or ε-caprolactone, resulted in graft copolymers with the desired functionalization pattern. The materials were characterized using Fourier-transform infrared spectroscopy, 1H- and 13C- nuclear magnetic resonance spectroscopy, size exclusion chromatography as well as X-ray diffraction, and differential scanning calorimetry. PCL-based copolymers exhibited distinct melting point as well as a crystalline phase of up to 47%, while copolymers with PLA segments were highly amorphous, showing a broad amorphous reflex in the XRD spectra, and no melting or crystallization points were discernible using differential scanning calorimetry. Full article
(This article belongs to the Section Biobased and Biodegradable Polymers)
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19 pages, 3315 KiB  
Article
Microwave-Assisted Hierarchically Grown Flake-like NiCo Layered Double Hydroxide Nanosheets on Transitioned Polystyrene towards Triboelectricity-Driven Self-Charging Hybrid Supercapacitors
by Seungju Jo, Narasimharao Kitchamsetti, Hyunwoo Cho and Daewon Kim
Polymers 2023, 15(2), 454; https://doi.org/10.3390/polym15020454 - 15 Jan 2023
Cited by 15 | Viewed by 2185
Abstract
Recently, there is a need to explore the utilization of various heterostructures using the designed nanocomposites and tuning the surfaces of electrodes for improving the electrochemical performance of supercapacitors (SC). In this work, a novel approach is successfully employed through a facile two-step [...] Read more.
Recently, there is a need to explore the utilization of various heterostructures using the designed nanocomposites and tuning the surfaces of electrodes for improving the electrochemical performance of supercapacitors (SC). In this work, a novel approach is successfully employed through a facile two-step synthetic route with the assistance of a microwave for only 1 min. Depending on the glass transition of a polystyrene (PS) substrate and electrochemical deposition (ECD) of electroactive Ni-Co layered double hydroxides (LDHs), a hierarchically designed flake-like morphology can be readily prepared to enhance the surface-active sites, which allows a rhombohedral Ni-Co LDHs electrode to obtain superior electrochemical properties. Further, the interactions between electrode and electrolyte during the diffusion of ions are highly simplified using multiple enhanced electroactive sites and shorter pathways for electron transfer. The unique surface architecture of the PS substrate and the synergistic effect of the bimetallic components in Ni-Co LDHs enable this substrate to obtain desired electrochemical activity in charge storage systems. The optimized MWC Co0.5Ni0.5 electrode exhibited an areal capacity of 100 µAh/cm2 at a current density of 1 mA/cm2 and a remarkable capacity retention of 91.2% over 5000 continuous charging and discharging cycles due to its remarkable synergistic effect of abundant faradaic redox reaction kinetics. The HSC device is assembled with the combination of optimized MWC Co0.5Ni0.5 and activated carbon as a positive and negative electrode, respectively. Further, the electrochemical test results demonstrated that MWC Co0.5Ni0.5 //AC HSC device showed a high areal capacitance of 531.25 mF/cm2 at a current density of 5 mA/cm2. In addition, the fabricated an aqueous HSC device showed a power density of 16 mW/cm2 at an energy density of 0.058 mWh/cm2, along with the remarkable capacity retention of 82.8% even after 10,000 continuous charging and discharging cycles. Moreover, the assembled hybrid supercapacitor (HSC) device is integrated with a triboelectric nanogenerator (TENG) for the development of energy conversion and storage systems. Not only an extensive survey of materials but also an innovative solution for recent progress can confirm the wide range of potential SC applications. Remarkably, this study is a new way of constructing self-powered energy storage systems in the field of sustainable wearable electronics and future smart sensing systems. Full article
(This article belongs to the Special Issue Polymers for Energy and Environmental Applications)
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10 pages, 2372 KiB  
Article
Research on the Change in Chemical Composition and Fungal Resistance of Moso Bamboo with Heat Treatment
by Wangwang Yu and Yong Wang
Polymers 2023, 15(2), 453; https://doi.org/10.3390/polym15020453 - 15 Jan 2023
Cited by 3 | Viewed by 1783
Abstract
Bamboo, as a potential alternative to biomass materials, has gained more attention from the bamboo manufacturing industry in China. However, the drawbacks, such as the dimensional instability, and low antifungal and hydrophilic properties of bamboo, inhibit its application and shorten its service life. [...] Read more.
Bamboo, as a potential alternative to biomass materials, has gained more attention from the bamboo manufacturing industry in China. However, the drawbacks, such as the dimensional instability, and low antifungal and hydrophilic properties of bamboo, inhibit its application and shorten its service life. The objective of this work was to analyze the change in chemical components and fungal resistance of moso bamboo with heat treatment. For this objective, moso bamboo specimens were thermally modified in an oven at different temperatures for a fixed duration. The results showed that the parenchymal cells distorted and deformed in comparison to the control after thermal modification. After thermal modification in an oven, the crystallinity index increased from 39% to 53%. Owing to the thermal modification, the hemicellulose and cellulose relative content decreased, as confirmed by FTIR and XPS analysis. Thus, the dimensional stability and antifungal properties of the thermally modified bamboo specimens improved. Full article
(This article belongs to the Special Issue Wood Polymer Composites: Processing, Properties, and Applications)
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15 pages, 4705 KiB  
Article
Oil Adsorption Kinetics of Calcium Stearate-Coated Kapok Fibers
by Aimee Lorraine M. Blaquera, Marvin U. Herrera, Ronniel D. Manalo, Monet Concepcion Maguyon-Detras, Cybelle Concepcion M. Futalan and Mary Donnabelle L. Balela
Polymers 2023, 15(2), 452; https://doi.org/10.3390/polym15020452 - 15 Jan 2023
Cited by 6 | Viewed by 3036
Abstract
This study used a simple and efficient dipping method to prepare oleophilic calcium stearate-coated kapok fibers (CaSt2-KF) with improved hydrophobicity. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) confirmed the deposition of calcium stearate particles on [...] Read more.
This study used a simple and efficient dipping method to prepare oleophilic calcium stearate-coated kapok fibers (CaSt2-KF) with improved hydrophobicity. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) confirmed the deposition of calcium stearate particles on the surface of the kapok fibers. This led to higher surface roughness and improved static water contact angle of 137.4°. The calcium stearate-coated kapok fibers exhibited comparable sorption capacities for kerosene, diesel, and palm oil. However, the highest sorption capacity of 59.69 g/g was observed for motor oil at static conditions. For motor oil in water, the coated fibers exhibited fast initial sorption and a 65% removal efficiency after 30 s. At equilibrium, CaSt2-KF attained a sorption capacity of 33.9 g/g and 92.5% removal efficiency for motor oil in water. The sorption kinetics of pure motor oil and motor oil in water follows the pseudo-second-order kinetic model, and the Elovich model further described chemisorption. Intraparticle diffusion and liquid film diffusion were both present, with the latter being the predominant diffusion mechanism during motor oil sorption. Full article
(This article belongs to the Special Issue Functional Nano/Microfiber Based Polymer Materials)
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19 pages, 705 KiB  
Review
Polysaccharides for Biodegradable Packaging Materials: Past, Present, and Future (Brief Review)
by Kristine V. Aleksanyan
Polymers 2023, 15(2), 451; https://doi.org/10.3390/polym15020451 - 15 Jan 2023
Cited by 27 | Viewed by 6614
Abstract
The ecological problems emerging due to accumulation of non-biodegradable plastics are becoming more and more urgent. This problem can be solved by the development of biodegradable materials which will replace the non-biodegradable ones. Among numerous approaches in this field, there is one proposing [...] Read more.
The ecological problems emerging due to accumulation of non-biodegradable plastics are becoming more and more urgent. This problem can be solved by the development of biodegradable materials which will replace the non-biodegradable ones. Among numerous approaches in this field, there is one proposing the use of polysaccharide-based materials. These polymers are biodegradable, non-toxic, and obtained from renewable resources. This review opens discussion about the application of polysaccharides for the creation of biodegradable packaging materials. There are numerous investigations developing new formulations using cross-linking of polymers, mixing with inorganic (metals, metal oxides, clays) and organic (dyes, essential oils, extracts) compounds. The main emphasis in the present work is made on development of the polymer blends consisting of cellulose, starch, chitin, chitosan, pectin, alginate, carrageenan with some synthetic polymers, polymers of natural origin, and essential oils. Full article
(This article belongs to the Special Issue Biodegradable Materials: Prospects)
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13 pages, 4140 KiB  
Article
Analysis of the Structure and the Thermal Conductivity of Semi-Crystalline Polyetheretherketone/Boron Nitride Sheet Composites Using All-Atom Molecular Dynamics Simulation
by Yuna Oh, Kwak Jin Bae, Yonjig Kim and Jaesang Yu
Polymers 2023, 15(2), 450; https://doi.org/10.3390/polym15020450 - 14 Jan 2023
Cited by 4 | Viewed by 2859
Abstract
Thermal transport simulations were performed to investigate the important factors affecting the thermal conductivity based on the structure of semi-crystalline polyetheretherketone (PEEK), and the addition of boron nitride (BN) sheets. The molecular-level structural analysis facilitated the prediction of the thermal conductivity of the [...] Read more.
Thermal transport simulations were performed to investigate the important factors affecting the thermal conductivity based on the structure of semi-crystalline polyetheretherketone (PEEK), and the addition of boron nitride (BN) sheets. The molecular-level structural analysis facilitated the prediction of the thermal conductivity of the optimal structure of PEEK reflecting the best parameter value of the length of amorphous chains, and the ratio of linkage conformations, such as loops, tails, and bridges. It was found that the long heat transfer paths of polymer chains were induced by the addition of BN sheets, which led to the improvement of the thermal conductivities of the PEEK/BN composites. In addition, the convergence of the thermal conductivities of the PEEK/BN composites in relation to BN sheet size was verified by the disconnection of the heat transfer path due to aggregation of the BN sheets. Full article
(This article belongs to the Special Issue Advanced Polymer Composite Materials: Processing, Modeling, Properties and Applications II)
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17 pages, 4192 KiB  
Article
Synthesis of Hyperbranched Flame Retardants with Varied Branched Chains’ Rigidity and Performance of Modified Epoxy Resins
by Jingyuan Hu, Liyue Zhang, Mingxuan Chen, Jinyue Dai, Na Teng, Hongchi Zhao, Xinwu Ba and Xiaoqing Liu
Polymers 2023, 15(2), 449; https://doi.org/10.3390/polym15020449 - 14 Jan 2023
Cited by 4 | Viewed by 1979
Abstract
To overcome the high flammability and brittleness of epoxy resins without sacrificing their glass transition temperature (Tg) and mechanical properties, three epoxy-terminated hyperbranched flame retardants (EHBFRs) with a rigid central core and different branches, named EHBFR-HB, EHBFR-HCM, and EHBFR-HBM, were [...] Read more.
To overcome the high flammability and brittleness of epoxy resins without sacrificing their glass transition temperature (Tg) and mechanical properties, three epoxy-terminated hyperbranched flame retardants (EHBFRs) with a rigid central core and different branches, named EHBFR-HB, EHBFR-HCM, and EHBFR-HBM, were synthesized. After chemical structure characterization, the synthesized EHBFRs were introduced into the diglycidyl ether of bisphenol A (DGEBA) and cured with 4, 4-diaminodiphenylmethane (DDM). The compatibility, thermal stability, mechanical properties, and flame retardancy of the resultant resins were evaluated. Results showed that all three EHBFRs could significantly improve the fire safety of cured resins, and 30 wt. % of EHBFRs (less than 1.0 wt. % phosphorus content) endowed cured DGEBA with a UL-94 V-0 rating. In addition, the increased rigidity of branches in EHBFRs could increase the flexural strength and modulus of cured resins, and the branches with appropriate rigidity were also beneficial for improving their room temperature impact strength and Tg. Full article
(This article belongs to the Special Issue Modification and Study on the Properties of Epoxy Resin)
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17 pages, 3061 KiB  
Article
Polyethyleneglycol-Betulinic Acid (PEG-BA) Polymer-Drug Conjugate Induces Apoptosis and Antioxidation in a Biological Model of Pancreatic Cancer
by Karabo Sekopi Mosiane, Ekene Emmanuel Nweke, Mohammed Balogun and Pascaline Nanga Fru
Polymers 2023, 15(2), 448; https://doi.org/10.3390/polym15020448 - 14 Jan 2023
Cited by 9 | Viewed by 2149
Abstract
Pancreatic cancer (PC) is one of the most aggressive solid malignancies with poor treatment response and low survival rates. Herbal medicines such as betulinic acid (BA) have shown potential in treating various solid tumours, but with limitations that can be circumvented by polymer-drug [...] Read more.
Pancreatic cancer (PC) is one of the most aggressive solid malignancies with poor treatment response and low survival rates. Herbal medicines such as betulinic acid (BA) have shown potential in treating various solid tumours, but with limitations that can be circumvented by polymer-drug conjugation. Polyethylene glycol-BA (PEG-BA) polymer-drug conjugate has previously shown selective anticancer activity against PC cells. Here, we elucidate the mechanism of cell death and the cell death pathway, anti-inflammatory and antioxidant activities of PEG-BA. PEG-BA induced apoptotic cell death by arresting MIA-PaCa-2 cells in the Sub-G1 phase of the cell cycle compared with BA and untreated cells (39.50 ± 5.32% > 19.63 ± 4.49% > 4.57 ± 0.82%). NFκB/p65 protein expression was moderately increased by PEG-BA (2.70 vs. 3.09 ± 0.42 ng/mL; p = 0.1521). However, significant (p < 0.05) overexpression of the proapoptotic genes TNF (23.72 ± 1.03) and CASPASE 3 (12,059.98 ± 1.74) compared with untreated cells was notable. The antioxidant potential of PEG-BA was greater (IC50 = 15.59 ± 0.64 µM) compared with ascorbic acid (25.58 ± 0.44 µM) and BA-only (>100 µM) and further confirmed with the improved reduction of hydroperoxide levels compared with BA-only (518.80 ± 25.53 µM vs. 542.43 ± 9.70 µM). In conclusion, PEG-BA activated both the intrinsic and extrinsic pathways of apoptosis and improved antioxidant activities in PC cells, suggesting enhanced anticancer activity upon conjugation. Full article
(This article belongs to the Special Issue Advanced Bio-Based Polymers and Nanocomposites)
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13 pages, 2347 KiB  
Article
Zirconium Phosphate Assisted Phosphoric Acid Co-Catalyzed Hydrolysis of Lignocellulose for Enhanced Extraction of Nanocellulose
by Hanchen Wang, Jiayin Wu, Yuan Lian, Yonggui Li, Biao Huang and Qilin Lu
Polymers 2023, 15(2), 447; https://doi.org/10.3390/polym15020447 - 14 Jan 2023
Cited by 6 | Viewed by 1922
Abstract
The high mechanical strength, large specific surface area, favorable biocompatibility, and degradability of nanocellulose (CNC) enable it to be a potential alternative to petroleum-based materials. However, the traditional preparation of CNCs requires a large amount of strong acid, which poses a serious challenge [...] Read more.
The high mechanical strength, large specific surface area, favorable biocompatibility, and degradability of nanocellulose (CNC) enable it to be a potential alternative to petroleum-based materials. However, the traditional preparation of CNCs requires a large amount of strong acid, which poses a serious challenge to equipment maintenance, waste liquid recycling, and economics. In this study, a solid and easily recoverable zirconium phosphate (ZrP) was used to assist in the phosphoric acid co-catalyzed hydrolysis of lignocellulose for extracting CNCs. Due to the presence of acidic phosphate groups, ZrP has a strong active center with a high catalytic activity. With the assistance of ZrP, the amount of phosphoric acid used in the reaction is significantly reduced, improving the equipment’s durability and economic efficiency. The effects of the process conditions investigated were the phosphate acid concentration, reaction temperature, and reaction time on the yield of CNCs. The Box–Behnken design (BBD) method from the response surface methodology (RSM) was applied to investigate and optimize the preparation conditions. The optimized pre-treatment conditions were 49.27% phosphoric acid concentration, 65.38 °C reaction temperature, and 5 h reaction time with a maximal cellulose yield (48.33%). The obtained CNCs show a granular shape with a length of 40~50 nm and a diameter of 20~30 nm, while its high zeta potential (−24.5 mV) make CNCs present a stable dispersion in aqueous media. Moreover, CNCs have a high crystallinity of 78.70% within the crystal type of cellulose Ⅰ. As such, this study may pioneer the horizon for developing a green method for the efficient preparation of CNC, and it is of great significance for CNCs practical production process. Full article
(This article belongs to the Special Issue Cellulose Nanocrystals: Synthesis, Functional Properties and Applications)
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13 pages, 5094 KiB  
Article
Effect of Silica-Modified Aluminum Oxide Abrasion on Adhesion to Dentin, Using Total-Etch and Self-Etch Systems
by Shifra Levartovsky, Benny Ferdman, Nahawand Safadi, Tujan Hanna, Eran Dolev and Raphael Pilo
Polymers 2023, 15(2), 446; https://doi.org/10.3390/polym15020446 - 14 Jan 2023
Cited by 2 | Viewed by 2777
Abstract
This study compared the shear bond strength (SBS) and micromorphology of composite resin to human dentin after pre-treatment with silica-modified aluminum oxide air abrasion. Forty-six molar teeth were treated with either Scotchbond Multi-Purpose (SCMP) or Clearfil SE Bond (CLSE) adhesive. Buccal surfaces were [...] Read more.
This study compared the shear bond strength (SBS) and micromorphology of composite resin to human dentin after pre-treatment with silica-modified aluminum oxide air abrasion. Forty-six molar teeth were treated with either Scotchbond Multi-Purpose (SCMP) or Clearfil SE Bond (CLSE) adhesive. Buccal surfaces were pre-treated with the CoJet air abrasion system (SB), and lingual surfaces were controls. The adhesion of light-cured resin composite to the treated dentin surface was evaluated with SBS. After debonding, substrate surfaces were examined with an optical microscope for failure analysis. In addition, 15 molar teeth were sectioned and randomly assigned to one of five groups, according to the dentin surface pre-treatment and adhesive type, and examined with high-vacuum scanning electron microscopy/energy dispersive X-rays (SEM/EDS). The type of adhesive had a significant effect on SBS (p = 0.000); CLSE had the highest values. SB did not affect SBS (p = 0.090). SEM/EDS revealed residual aluminum and/or silicon on all dentin surfaces after SB, except for the control. Treatment with 32% phosphoric acid in the SCMP adhesive decreased the amounts of aluminum and silicon compared to SB dentin only, whereas CLSE resulted in similar quantities of aluminum and silicon as air-abraded dentin. The results of this study indicate that CLSE might have a higher bond strength to dentin than SCMP. Pre-treatment with SB does not appear to affect bonding strength. Full article
(This article belongs to the Special Issue Polymer Composites in Biomedical Applications II)
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19 pages, 4683 KiB  
Article
Ultimate and Deflection Performance of Concrete Beams Strengthened in Flexure with Basalt-Textile-Reinforced Polymer Mortar
by Jun Deng, Minting Zhong, Zhuojian Zhang and Miaochang Zhu
Polymers 2023, 15(2), 445; https://doi.org/10.3390/polym15020445 - 14 Jan 2023
Viewed by 1673
Abstract
This paper presents an investigation into the ultimate and serviceability behavior of concrete beams strengthened in flexure with basalt-textile-reinforced polymer mortar (BTRM). The bond performance at the interface between the BTRM and concrete was studied by performing single shear tests, and the effectiveness [...] Read more.
This paper presents an investigation into the ultimate and serviceability behavior of concrete beams strengthened in flexure with basalt-textile-reinforced polymer mortar (BTRM). The bond performance at the interface between the BTRM and concrete was studied by performing single shear tests, and the effectiveness of using an adhesion promoter and impregnated resin for bond enhancement was explored. The results suggested that using an adhesion promoter and impregnated resin can improve the interfacial stress transfer and ensure the tensile failure of the basalt textile in BTRM. Afterward, four-point bending tests were conducted to study the flexural performance of strengthened beams. It was found that the flexural strength of strengthened beams increased with the amount of textile, and the strength increase was more prominent for the strengthened beams with end anchorages. The increase in the failure force was up to 37% for the beam strengthened with five layers of the textile and an end anchorage. The calculated flexural strength exhibited a percentage error of no more than 7% compared to the test results. In addition, the Bischoff-I Equation can closely estimate the effective moment of inertia and provide an accurate prediction of deflection for strengthened beams. Full article
(This article belongs to the Section Polymer Applications)
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21 pages, 4576 KiB  
Article
Preparation of Self-Assembled Nanoparticle–Polymer Hybrids from Modified Silica Nanoparticles and Polystyrene-Block-Polyacrylic Acid Vesicles via the Co-Precipitation Method
by Jil Mann, Georg Garnweitner and Carsten Schilde
Polymers 2023, 15(2), 444; https://doi.org/10.3390/polym15020444 - 14 Jan 2023
Cited by 4 | Viewed by 3096
Abstract
Nanoparticle–polymer hybrids are becoming increasingly important because seemingly contrasting properties, such as mechanical stability and high elasticity, can be combined into one material. In particular, hybrids made of self-assembled polymers are of growing interest since they exhibit high structural precision and diversity and [...] Read more.
Nanoparticle–polymer hybrids are becoming increasingly important because seemingly contrasting properties, such as mechanical stability and high elasticity, can be combined into one material. In particular, hybrids made of self-assembled polymers are of growing interest since they exhibit high structural precision and diversity and the subsequent reorganization of the nanoparticles is possible. In this work, we show, for the first time, how hybrids of silica nanoparticles and self-assembled vesicles of polystyrene-block-polyacrylic acid can be prepared using the simple and inexpensive method of co-precipitation, highlighting in particular the challenges of using silica instead of other previously well-researched materials, such as gold. The aim was to investigate the influence of the type of modification and the particle size of the silica nanoparticles on the encapsulation and structure of the polymer vesicles. For this purpose, we first needed to adjust the surface properties of the nanoparticles, which we achieved with a two-step modification procedure using APTES and carboxylic acids of different chain lengths. We found that silica nanoparticles modified only with APTES could be successfully encapsulated, while those modified with APTES and decanoic acid resulted in vesicle agglomeration and poor encapsulation due to their strong hydrophobicity. In contrast, no negative effects were observed when different particle sizes (20 nm and 45 nm) were examined. Full article
(This article belongs to the Special Issue Advanced Polymers and Composites: New Functionalities and Sustainability)
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12 pages, 3879 KiB  
Article
Combined Additive and Laser-Induced Processing of Functional Structures for Monitoring under Deformation
by Tawakalt Mayowa Akintola, Balaji Krishna Kumar and Tarik Dickens
Polymers 2023, 15(2), 443; https://doi.org/10.3390/polym15020443 - 14 Jan 2023
Cited by 5 | Viewed by 2060
Abstract
This research introduces a readily available and non-chemical combinatorial production approach, known as the laser-induced writing process, to achieve laser-processed conductive graphene traces. The laser-induced graphene (LIG) structure and properties can be improved by adjusting the laser conditions and printing parameters. This method [...] Read more.
This research introduces a readily available and non-chemical combinatorial production approach, known as the laser-induced writing process, to achieve laser-processed conductive graphene traces. The laser-induced graphene (LIG) structure and properties can be improved by adjusting the laser conditions and printing parameters. This method demonstrates the ability of laser-induced graphene (LIG) to overcome the electrothermal issues encountered in electronic devices. To additively process the PEI structures and the laser-induced surface, a high-precision laser nScrypt printer with different power, speed, and printing parameters was used. Raman spectroscopy and scanning electron microscopy analysis revealed similar results for laser-induced graphene morphology and structural chemistry. Significantly, the 3.2 W laser-induced graphene crystalline size (La; 159 nm) is higher than the higher power (4 W; 29 nm) formation due to the surface temperature and oxidation. Under four-point probe electrical property measurements, at a laser power of 3.8 W, the resistivity of the co-processed structure was three orders of magnitude larger. The LIG structure and property improvement are possible by varying the laser conditions and the printing parameters. The lowest gauge factor (GF) found was 17 at 0.5% strain, and the highest GF found was 141.36 at 5%. Full article
(This article belongs to the Special Issue Laser Processing of Polymers: Induced Effects and Functionalization)
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