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Volume 11
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Polymers, Volume 11, Issue 4 (April 2019) – 174 articles

Cover Story (view full-size image): Volatile organic components pose a significant danger to human health and, especially, formaldehyde (HCHO) is produced in many natural and synthetic processes and is considered a prime household air pollutant. To destroy HCHO at room temperature, platinum–nickel nanoparticles were directly synthesized on polydopamine-coated poly(methyl methacrylate) electrospun fibers without any excessive oxide. These formed a filter-like membrane that was able to decompose 90% of the formaldehyde at very low dosage with high durability. The sheet-like membrane enables facile handling and its low air resistance allows for minimal air flow losses when integrated, for example, in an air conditioning unit. View this paper
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35 pages, 3663 KiB  
Review
Polymeric Nanoparticles in Gene Therapy: New Avenues of Design and Optimization for Delivery Applications
by Raj Rai, Saniya Alwani and Ildiko Badea
Polymers 2019, 11(4), 745; https://doi.org/10.3390/polym11040745 - 25 Apr 2019
Cited by 235 | Viewed by 19206
Abstract
The field of polymeric nanoparticles is quickly expanding and playing a pivotal role in a wide spectrum of areas ranging from electronics, photonics, conducting materials, and sensors to medicine, pollution control, and environmental technology. Among the applications of polymers in medicine, gene therapy [...] Read more.
The field of polymeric nanoparticles is quickly expanding and playing a pivotal role in a wide spectrum of areas ranging from electronics, photonics, conducting materials, and sensors to medicine, pollution control, and environmental technology. Among the applications of polymers in medicine, gene therapy has emerged as one of the most advanced, with the capability to tackle disorders from the modern era. However, there are several barriers associated with the delivery of genes in the living system that need to be mitigated by polymer engineering. One of the most crucial challenges is the effectiveness of the delivery vehicle or vector. In last few decades, non-viral delivery systems have gained attention because of their low toxicity, potential for targeted delivery, long-term stability, lack of immunogenicity, and relatively low production cost. In 1987, Felgner et al. used the cationic lipid based non-viral gene delivery system for the very first time. This breakthrough opened the opportunity for other non-viral vectors, such as polymers. Cationic polymers have emerged as promising candidates for non-viral gene delivery systems because of their facile synthesis and flexible properties. These polymers can be conjugated with genetic material via electrostatic attraction at physiological pH, thereby facilitating gene delivery. Many factors influence the gene transfection efficiency of cationic polymers, including their structure, molecular weight, and surface charge. Outstanding representatives of polymers that have emerged over the last decade to be used in gene therapy are synthetic polymers such as poly(l-lysine), poly(l-ornithine), linear and branched polyethyleneimine, diethylaminoethyl-dextran, poly(amidoamine) dendrimers, and poly(dimethylaminoethyl methacrylate). Natural polymers, such as chitosan, dextran, gelatin, pullulan, and synthetic analogs, with sophisticated features like guanidinylated bio-reducible polymers were also explored. This review outlines the introduction of polymers in medicine, discusses the methods of polymer synthesis, addressing top down and bottom up techniques. Evaluation of functionalization strategies for therapeutic and formulation stability are also highlighted. The overview of the properties, challenges, and functionalization approaches and, finally, the applications of the polymeric delivery systems in gene therapy marks this review as a unique one-stop summary of developments in this field. Full article
(This article belongs to the Special Issue Polymers in Gene Delivery)
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14 pages, 3399 KiB  
Article
In vitro Comparative Study of Fibroblastic Behaviour on Polymethacrylate (PMMA) and Lithium Disilicate Polymer Surfaces
by Cristina Herráez-Galindo, María Rizo-Gorrita, Irene Luna-Oliva, María-Ángeles Serrera-Figallo, Raquel Castillo-Oyagüe and Daniel Torres-Lagares
Polymers 2019, 11(4), 744; https://doi.org/10.3390/polym11040744 - 25 Apr 2019
Cited by 13 | Viewed by 3644
Abstract
Polymethyl methacrylate (PMMA) and lithium disilicate are widely used materials in the dental field. PMMA is mainly used for the manufacture of removable prostheses; however, with the incorporation of CAD-CAM technology, new applications have been introduced for this material, including as a provisional [...] Read more.
Polymethyl methacrylate (PMMA) and lithium disilicate are widely used materials in the dental field. PMMA is mainly used for the manufacture of removable prostheses; however, with the incorporation of CAD-CAM technology, new applications have been introduced for this material, including as a provisional implant attachment. Lithium disilicate is considered the gold standard for definitive attachment material. On the other hand, PMMA has begun to be used in clinics as a provisional attachment until the placement of a definitive one occurs. Although there are clinical studies regarding its use, there are few studies on cell reorganization around this type of material. This is why we carried out an in vitro comparative study using discs of both materials in which human gingival fibroblasts (HGFs) were cultured. After processing them, we analyzed various cellular parameters (cell count, cytoskeleton length, core size and coverage area). We analyzed the surface of the discs together with their composition. The results obtained were mostly not statistically significant, which shows that the qualities of PMMA make it a suitable material as an implant attachment. Full article
(This article belongs to the Special Issue Biomedical Polymer Materials)
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14 pages, 6214 KiB  
Article
Pluronic F127-Folate Coated Super Paramagenic Iron Oxide Nanoparticles as Contrast Agent for Cancer Diagnosis in Magnetic Resonance Imaging
by Hieu Vu-Quang, Mads Sloth Vinding, Thomas Nielsen, Marcus Görge Ullisch, Niels Chr. Nielsen, Dinh-Truong Nguyen and Jørgen Kjems
Polymers 2019, 11(4), 743; https://doi.org/10.3390/polym11040743 - 25 Apr 2019
Cited by 50 | Viewed by 8636
Abstract
Contrast agents have been widely used in medicine to enhance contrast in magnetic resonance imaging (MRI). Among them, super paramagnetic iron oxide nanoparticles (SPION) have been reported to have low risk in clinical use. In our study, F127-Folate coated SPION was fabricated in [...] Read more.
Contrast agents have been widely used in medicine to enhance contrast in magnetic resonance imaging (MRI). Among them, super paramagnetic iron oxide nanoparticles (SPION) have been reported to have low risk in clinical use. In our study, F127-Folate coated SPION was fabricated in order to efficiently target tumors and provide imaging contrast in MRI. SPION alone have an average core size of 15 nm. After stabilizing with Pluronic F127, the nanoparticles reached a hydrodynamic size of 180 nm and dispersed well in various kinds of media. The F127-Folate coated SPION were shown to specifically target folate receptor expressing cancer cells by flow cytometry analysis, confocal laser scanning microscope, as well as in vitro MRI. Furthermore, in vivo MRI images have shown the enhanced negative contrast from the F127-Folate coated SPION in tumor-bearing mice. In conclusion, our F127-Folate coated SPION have shown great potential as a contrast agent in MRI, as well as in the combination with drug delivery for cancer therapy. Full article
(This article belongs to the Special Issue Intrinsically Biocompatible Polymer Systems)
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16 pages, 3272 KiB  
Article
Synthesis and Characterization of Covalently Crosslinked pH-Responsive Hyaluronic Acid Nanogels: Effect of Synthesis Parameters
by Sheila Maiz-Fernández, Leyre Pérez-Álvarez, Leire Ruiz-Rubio, Raúl Pérez González, Virginia Sáez-Martínez, Jesica Ruiz Pérez and José Luis Vilas-Vilela
Polymers 2019, 11(4), 742; https://doi.org/10.3390/polym11040742 - 24 Apr 2019
Cited by 38 | Viewed by 7101
Abstract
Stable hyaluronic acid nanogels were obtained following the water-in-oil microemulsion method by covalent crosslinking with three biocompatible crosslinking agents: Divinyl sulfone, 1,4-butanediol diglycidyl ether (BDDE), and poly(ethylene glycol) bis(amine). All nanoparticles showed a pH-sensitive swelling behavior, according to the pKa value of hyaluronic [...] Read more.
Stable hyaluronic acid nanogels were obtained following the water-in-oil microemulsion method by covalent crosslinking with three biocompatible crosslinking agents: Divinyl sulfone, 1,4-butanediol diglycidyl ether (BDDE), and poly(ethylene glycol) bis(amine). All nanoparticles showed a pH-sensitive swelling behavior, according to the pKa value of hyaluronic acid, as a consequence of the ionization of the carboxylic moieties, as it was corroborated by zeta potential measurements. QELS studies were carried out to study the influence of the chemical structure of the crosslinking agents on the particle size of the obtained nanogels. In addition, the effect of the molecular weight of the biopolymer and the degree of crosslinking on the nanogels dimensions was also evaluated for BDDE crosslinked nanoparticles, which showed the highest pH-responsive response. Full article
(This article belongs to the Special Issue Hyaluronic Acid-Based Polymers and Biomaterials)
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16 pages, 4204 KiB  
Article
Effect of Silane Treatment on Mechanical Properties of Polyurethane/Mesoscopic Fly Ash Composites
by Chuanrui Qin, Wei Lu, Zhenglong He, Guansheng Qi, Jinliang Li and Xiangming Hu
Polymers 2019, 11(4), 741; https://doi.org/10.3390/polym11040741 - 24 Apr 2019
Cited by 18 | Viewed by 4334
Abstract
In view of the accidents such as rock mass breakage, roof fall and coal slide in coal mines, polyurethane/mesoscopic fly ash (PU/MFA) reinforcement materials were produced from polymethylene polyphenylene isocyanate (PAPI), the polyether polyol, flame retardant, and MFA using stannous octanate as a [...] Read more.
In view of the accidents such as rock mass breakage, roof fall and coal slide in coal mines, polyurethane/mesoscopic fly ash (PU/MFA) reinforcement materials were produced from polymethylene polyphenylene isocyanate (PAPI), the polyether polyol, flame retardant, and MFA using stannous octanate as a catalyst. 3-Glycidoxypropyltrimethoxysilane (GPTMS) was grafted on MFA surface, aiming to improve the mechanical properties of PU/MFA composites. The analyses of infrared spectroscopy and compression resistance reveal that the GPTMS can be successfully attached to the surface of MFA, and the optimum modification dosage of GPTMS to MFA is 2.5 wt. % (weight percent). On this basis, the effect of GPTMS on the mechanical properties of PU/MFA reinforcement materials during the curing process was systematically investigated through a compression test, a fracture toughness test, a three-point bending test, a bond property test, and a dynamic mechanics analysis. The results show that the compression property, fracture toughness, maximum flexural strength, and bond strength of PU/MFA composites increase by 21.6%, 10.1%, 8.8%, and 19.3%, respectively, compared with the values before the modification. Furthermore, the analyses of scanning electron microscope and dynamic mechanics suggest that the coupling agent GPTMS can successfully improve the mechanical properties of PU/MFA composites because it eliminates the stress concentration and exerts a positive effect on the crosslink density and hardness of PU/MFA composites. Full article
(This article belongs to the Collection Silicon-Containing Polymeric Materials)
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15 pages, 4333 KiB  
Article
Characterization of Reduced and Surface-Modified Graphene Oxide in Poly(Ethylene-co-Butyl Acrylate) Composites for Electrical Applications
by Carmen Cobo Sánchez, Martin Wåhlander, Mattias Karlsson, Diana C. Marin Quintero, Henrik Hillborg, Eva Malmström and Fritjof Nilsson
Polymers 2019, 11(4), 740; https://doi.org/10.3390/polym11040740 - 24 Apr 2019
Cited by 7 | Viewed by 3911
Abstract
Promising electrical field grading materials (FGMs) for high-voltage direct-current (HVDC) applications have been designed by dispersing reduced graphene oxide (rGO) grafted with relatively short chains of poly (n-butyl methacrylate) (PBMA) in a poly(ethylene-co-butyl acrylate) (EBA) matrix. All rGO-PBMA composites [...] Read more.
Promising electrical field grading materials (FGMs) for high-voltage direct-current (HVDC) applications have been designed by dispersing reduced graphene oxide (rGO) grafted with relatively short chains of poly (n-butyl methacrylate) (PBMA) in a poly(ethylene-co-butyl acrylate) (EBA) matrix. All rGO-PBMA composites with a filler fraction above 3 vol.% exhibited a distinct non-linear resistivity with increasing electric field; and it was confirmed that the resistivity could be tailored by changing the PBMA graft length or the rGO filler fraction. A combined image analysis- and Monte-Carlo simulation strategy revealed that the addition of PBMA grafts improved the enthalpic solubility of rGO in EBA; resulting in improved particle dispersion and more controlled flake-to-flake distances. The addition of rGO and rGO-PBMAs increased the modulus of the materials up to 200% and the strain did not vary significantly as compared to that of the reference matrix for the rGO-PBMA-2 vol.% composites; indicating that the interphase between the rGO and EBA was subsequently improved. The new composites have comparable electrical properties as today’s commercial FGMs; but are lighter and less brittle due to a lower filler fraction of semi-conductive particles (3 vol.% instead of 30–40 vol.%). Full article
(This article belongs to the Special Issue Conducting Polymers)
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10 pages, 7681 KiB  
Article
Jetting Performance of Polyethylene Glycol and Reactive Dye Solutions
by Zhiyuan Tang, Kuanjun Fang, Yawei Song and Fuyun Sun
Polymers 2019, 11(4), 739; https://doi.org/10.3390/polym11040739 - 24 Apr 2019
Cited by 25 | Viewed by 5125
Abstract
The jetting performance of dye inks determines the image quality, production efficiency, and lifetime of the print head. In the present study, we explored the jetting performance of mixed solutions of polyethylene glycol (PEG) and reactive dye by testing the visible absorption spectra, [...] Read more.
The jetting performance of dye inks determines the image quality, production efficiency, and lifetime of the print head. In the present study, we explored the jetting performance of mixed solutions of polyethylene glycol (PEG) and reactive dye by testing the visible absorption spectra, rheological properties, and surface tension, in addition to the observation of droplet formation. The results indicate that PEG macromolecules could change the aggregate groups of Red 218 molecules into smaller ones through hydrophobic interactions and separation effect. The addition of PEG into the dye solution increased the viscosity and decreased the surface tension. In the whole shear rate range tested, the 10% and 20% PEG400, as well as the 30% PEG200 dye solutions, showed good Newtonian fluid behavior. PEG macromolecules improved the droplet formation of the dye solutions. Increasing the PEG400 concentration to 30% and 40% resulted in elimination of the formation of satellites and the formation of ideal droplets at 10,000 Hz jetting frequency. A 30% PEG600-dye solution with the Z value of 4.6 formed the best spherical droplets at 10,000 Hz and produced perfect color images on cotton fabrics. Full article
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16 pages, 1598 KiB  
Article
Fuzzy Optimization on the Synthesis of Chitosan-Graft-Polyacrylic Acid with Montmorillonite as Filler Material: A Case Study
by Angelo Earvin Sy Choi, Cybelle Morales Futalan and Jurng-Jae Yee
Polymers 2019, 11(4), 738; https://doi.org/10.3390/polym11040738 - 23 Apr 2019
Cited by 7 | Viewed by 3461
Abstract
In this paper, the synthesis of a chitosan–montmorillonite nanocomposite material grafted with acrylic acid is presented based on its function in a case study analysis. Fuzzy optimization is used for a multi-criteria decision analysis to determine the best desirable swelling capacity (Y [...] Read more.
In this paper, the synthesis of a chitosan–montmorillonite nanocomposite material grafted with acrylic acid is presented based on its function in a case study analysis. Fuzzy optimization is used for a multi-criteria decision analysis to determine the best desirable swelling capacity (YQ) of the material synthesis at its lowest possible variable cost. For YQ, the integrating the result’s cumulative uncertainty is an essential element to investigate the feasibility of the developed model equation. The Pareto set analysis is able to set the appropriate boundary limits for YQ and the variable cost. Two case studies are presented in determining the lowest possible cost: Case 1 for maximum YQ, and Case 2 for minimum YQ. These boundary limits were used in the fuzzy optimization to determine its global optimum results that achieved the overall satisfaction ratings of 67.2% (Case 1) and 52.3% (Case 2). The synthesis of the polyacrylic acid/chitosan material for Case 1 resulted in 305 g/g YQ and 10.8 USD/kg, while Case 2 resulted in 97 g/g YQ and 12.3 USD/kg. Thus, the fuzzy optimization approach proves to be a practical method for examining the best possible compromise solution based on the desired function to adequately synthesize a material. Full article
(This article belongs to the Special Issue Polymer Clay Nano-composites)
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15 pages, 4589 KiB  
Article
Tethered Semiflexible Polymer under Large Amplitude Oscillatory Shear
by Antonio Lamura and Roland G. Winkler
Polymers 2019, 11(4), 737; https://doi.org/10.3390/polym11040737 - 23 Apr 2019
Cited by 6 | Viewed by 3188
Abstract
The properties of a semiflexible polymer with fixed ends exposed to oscillatory shear flow are investigated by simulations. The two-dimensionally confined polymer is modeled as a linear bead-spring chain, and the interaction with the fluid is described by the Brownian multiparticle collision dynamics [...] Read more.
The properties of a semiflexible polymer with fixed ends exposed to oscillatory shear flow are investigated by simulations. The two-dimensionally confined polymer is modeled as a linear bead-spring chain, and the interaction with the fluid is described by the Brownian multiparticle collision dynamics approach. For small shear rates, the tethering of the ends leads to a more-or-less linear oscillatory response. However, at high shear rates, we found a strongly nonlinear reaction, with a polymer (partially) wrapped around the fixation points. This leads to an overall shrinkage of the polymer. Dynamically, the location probability of the polymer center-of-mass position is largest on a spatial curve resembling a limaçon, although with an inhomogeneous distribution. We found shear-induced modifications of the normal-mode correlation functions, with a frequency doubling at high shear rates. Interestingly, an even-odd asymmetry for the Cartesian components of the correlation functions appears, with rather similar spectra for odd x- and even y-modes and vice versa. Overall, our simulations yielded an intriguing nonlinear behavior of tethered semiflexible polymers under oscillatory shear flow. Full article
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9 pages, 2274 KiB  
Article
Surface-Controlled Molecular Self-Alignment in Polymer Actuators for Flexible Microrobot Applications
by Minsu Jang, Jun Sik Kim, Ji-Hun Kim, Do Hyun Bae, Min Jun Kim, Donghee Son, Yong-Tae Kim, Soong Ho Um, Yong Ho Kim and Jinseok Kim
Polymers 2019, 11(4), 736; https://doi.org/10.3390/polym11040736 - 23 Apr 2019
Cited by 2 | Viewed by 3800
Abstract
Polymer actuators are important components in lab-on-a-chip and micromechanical systems because of the inherent properties that result from their large and fast mechanical responses induced by molecular-level deformations (e.g., isomerization). They typically exhibit bending movements via asymmetric contraction or expansion with respect to [...] Read more.
Polymer actuators are important components in lab-on-a-chip and micromechanical systems because of the inherent properties that result from their large and fast mechanical responses induced by molecular-level deformations (e.g., isomerization). They typically exhibit bending movements via asymmetric contraction or expansion with respect to changes in environmental conditions. To enhance the mechanical properties of actuators, a strain gradient should be introduced by regulating the molecular alignment; however, the miniaturization of polymer actuators for microscale systems has raised concerns regarding the complexity of such molecular control. Herein, a novel method for the fabrication of micro-actuators using a simple molecular self-alignment method is presented. Amphiphilic molecules that consist of azobenzene mesogens were located between the hydrophilic and hydrophobic surfaces, which resulted in a splayed alignment. Thereafter, molecular isomerization on the surface induced a large strain gradient and bending movement of the actuator under ultraviolet-light irradiation. Moreover, the microelectromechanical systems allowed for the variation of the actuator size below the micron scale. The mechanical properties of the fabricated actuators such as the bending direction, maximum angle, and response time were evaluated with respect to their thicknesses and lengths. The derivatives of the polymer actuator microstructure may contribute to the development of novel applications in the micro-robotics field. Full article
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12 pages, 7487 KiB  
Article
Photo Actuation Performance of Nanotube Sheet Incorporated Azobenzene Crosslinked Liquid Crystalline Polymer Nanocomposite
by Meng Bi, Yifan He, Yuchang Wang, Wenlong Yang, Ban Qin, Jiaojiao Xu, Xiuxiu Wang, Binsong Wang, Yinmao Dong, Yachen Gao and Chensha Li
Polymers 2019, 11(4), 735; https://doi.org/10.3390/polym11040735 - 23 Apr 2019
Cited by 16 | Viewed by 4178
Abstract
Crosslinked liquid crystalline polymers (CLCPs) containing azobenzene (AZO-CLCPs) are a type of promising material due to their significance in the design of light-driven smart actuators. Developing AZO-CLCP composites by incorporating AZO-CLCPs with other materials is an effective way of enhancing their practicability. Herein, [...] Read more.
Crosslinked liquid crystalline polymers (CLCPs) containing azobenzene (AZO-CLCPs) are a type of promising material due to their significance in the design of light-driven smart actuators. Developing AZO-CLCP composites by incorporating AZO-CLCPs with other materials is an effective way of enhancing their practicability. Herein, we report an AZO-CLCP/CNT nanocomposite prepared by the in situ polymerization of diacrylates containing azobenzene chromophores on carbon nanotube (CNT) sheets. The liquid crystal phase structure of CLCP matrix was evidenced by the two-dimensional X-ray scattering. The prepared pure AZO-CLCP films and AZO-CLCP/CNT nanocomposite films demonstrated strong reversible photo-triggered deformation under the irradiation of UV light at 366 nm of wavelength, as a result of photo-induced isomerization of azobenzene moieties in the polymer network. But compared to pure AZO-CLCP films, the AZO-CLCP/CNT nanocomposite films could much more rapidly return to their initial shapes after the UV light irradiation was removed due to the elasticity effect of CNT sheets. The deformation behavior of AZO-CLCP/CNT nanocomposite films under the light irradiation was also different from that of the pure AZO-CLCP films due to the interfacial interaction between a polymer network and CNT sheet. Furthermore, incorporation of a CNT sheet remarkably increased the mechanical strength and robustness of the material. We also used this AZO-CLCP/CNT nanocomposite as a microvalve membrane actuator, which can be controlled by light, for a conceptual device of a microfluidic system. The results showed that this AZO-CLCP/CNT nanocomposite may have great potential in smart actuator applications for biological engineering, medical treatment, environment detection and microelectromechanical systems (MEMS), etc. Full article
(This article belongs to the Special Issue Polymer-CNT Nanocomposites)
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11 pages, 4309 KiB  
Article
An Albumin Biopassive Polyallylamine Film with Improved Blood Compatibility for Metal Devices
by Shuang Lin, Xin Li, Kebing Wang, Tengda Shang, Lei Zhou, Lu Zhang, Jin Wang and Nan Huang
Polymers 2019, 11(4), 734; https://doi.org/10.3390/polym11040734 - 23 Apr 2019
Cited by 9 | Viewed by 3515
Abstract
Nowadays, a variety of materials are employed to make numerous medical devices, including metals, polymers, ceramics, and others. Blood-contact devices are one of the major classes of these medical devices, and they have been widely applied in clinical settings. Blood-contact devices usually need [...] Read more.
Nowadays, a variety of materials are employed to make numerous medical devices, including metals, polymers, ceramics, and others. Blood-contact devices are one of the major classes of these medical devices, and they have been widely applied in clinical settings. Blood-contact devices usually need to have good mechanical properties to maintain clinical performance. Metal materials are one desirable candidate to fabricate blood-contact devices due to their excellent mechanical properties and machinability, although the blood compatibility of existing blood-contact devices is better than other medical devices, such as artificial joints and artificial crystals. However, blood coagulation still occurs when these devices are used in clinical settings. Therefore, it is necessary to develop a new generation of blood-contact devices with fewer complications, and the key factor is to develop novel biomaterials with good blood compatibility. In this work, one albumin biopassive polyallylamine film was successfully established onto the 316L stainless steel (SS) surface. The polyallylamine film was prepared by plasma polymerization in the vacuum chamber, and then polyallylamine film was annealed at 150 °C for 1 h. The chemical compositions of the plasma polymerized polyallylamine film (PPAa) and the annealed polyallylamine film (HT-PPAa) were characterized by Fourier transform infrared spectrum (FTIR). Then, the wettability, surface topography, and thickness of the PPAa and HT-PPAa were also evaluated. HT-PPAa showed increased stability when compared with PPAa film. The major amino groups remained on the surface of HT-PPAa after annealing, indicating that this could be a good platform for numerous molecules’ immobilization. Subsequently, the bovine serum albumin (BSA) was immobilized onto the HT-PPAa surface. The successful introduction of the BSA was confirmed by the FTIR and XPS detections. The blood compatibility of these modified films was evaluated by platelets adhesion and activation assays. The number of the platelets that adhered on BSA-modified HT-PPAa film was significantly decreased, and the activation degree of the adhered platelets was also decreased. These data revealed that the blood compatibility of the polyallylamine film was improved after BSA immobilized. This work provides a facile and effective approach to develop novel surface treatment for new-generation blood-contact devices with improved hemocompatibility. Full article
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23 pages, 4486 KiB  
Article
Graphene Oxide–Platinum Nanoparticle Nanocomposites: A Suitable Biocompatible Therapeutic Agent for Prostate Cancer
by Sangiliyandi Gurunathan, Muniyandi Jeyaraj, Min-Hee Kang and Jin-Hoi Kim
Polymers 2019, 11(4), 733; https://doi.org/10.3390/polym11040733 - 23 Apr 2019
Cited by 40 | Viewed by 6042
Abstract
Metal nanoparticles and the combination of metal nanoparticles with graphene oxide are widely used in environmental, agriculture, textile, and therapeutic applications. The effect of graphene oxide–green platinum nanoparticles (GO-PtNPs) on human prostate cancer cells (LNCaP) is unclear. Therefore, this study aimed to synthesize [...] Read more.
Metal nanoparticles and the combination of metal nanoparticles with graphene oxide are widely used in environmental, agriculture, textile, and therapeutic applications. The effect of graphene oxide–green platinum nanoparticles (GO-PtNPs) on human prostate cancer cells (LNCaP) is unclear. Therefore, this study aimed to synthesize a nanocomposite of GO-PtNPs and evaluate their effect on prostate cancer cells. Herein, we synthesized GO-PtNPs using vanillin and characterized GO-PtNPs. GO-PtNP cytotoxicity in LNCaP cells was demonstrated by measuring cell viability and proliferation. Both decreased in a dose-dependent manner compared to that by GO or PtNPs alone. GO-PtNP cytotoxicity was confirmed by increased lactate dehydrogenase release and membrane integrity loss. Oxidative stress induced by GO-PtNPs increased malondialdehyde, nitric oxide, and protein carbonyl contents. The effective reactive oxygen species generation impaired the cellular redox balance and eventually impaired mitochondria by decreasing the membrane potential and ATP level. The cytotoxicity to LNCaP cells was correlated with increased expression of proapoptotic genes (p53, p21, Bax, Bak, caspase 9, and caspase 3) and decreased levels of antiapoptotic genes (Bcl2 and Bcl-xl). Activation of the key regulators p53 and p21 inhibited the cyclin-dependent kinases Cdk2 and Cdk4, suggesting that p53 and p21 activation in GO-PtNP-treated cells caused genotoxic stress and apoptosis. The increased expression of genes involved in cell cycle arrest and DNA damage and repair, and increased levels of 8-oxo-deoxyguanosine and 8-oxoguanine suggested that GO-PtNPs potentially induce oxidative damage to DNA. Thus, GO-PtNPs are both cytotoxic and genotoxic. LNCaP cells appear to be more susceptible to GO-PtNPs than to GO or PtNPs. Therefore, GO-PtNPs have potential as an alternate and effective cancer therapeutic agent. Finally, this work shows that the combination of graphene oxide with platinum nanoparticles opens new perspectives in cancer therapy. However further detailed mechanistic studies are required to elucidate the molecular mechanism of GO-PtNPs induced cytotoxicity in prostate cancer. Full article
(This article belongs to the Special Issue Graphene-Polymer Composites II)
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14 pages, 2561 KiB  
Article
Ionic Liquid Composite Polybenzimidazol Membranes for High Temperature PEMFC Applications
by Jorge Escorihuela, Abel García-Bernabé, Álvaro Montero, Óscar Sahuquillo, Enrique Giménez and Vicente Compañ
Polymers 2019, 11(4), 732; https://doi.org/10.3390/polym11040732 - 22 Apr 2019
Cited by 43 | Viewed by 6409
Abstract
A series of proton exchange membranes based on polybenzimidazole (PBI) were prepared using the low cost ionic liquids (ILs) derived from 1-butyl-3-methylimidazolium (BMIM) bearing different anions as conductive fillers in the polymeric matrix with the aim of enhancing the proton conductivity of PBI [...] Read more.
A series of proton exchange membranes based on polybenzimidazole (PBI) were prepared using the low cost ionic liquids (ILs) derived from 1-butyl-3-methylimidazolium (BMIM) bearing different anions as conductive fillers in the polymeric matrix with the aim of enhancing the proton conductivity of PBI membranes. The composite membranes prepared by casting method (containing 5 wt. % of IL) exhibited good thermal, dimensional, mechanical, and oxidative stability for fuel cell applications. The effects of anion, temperature on the proton conductivity of phosphoric acid-doped membranes were systematically investigated by electrochemical impedance spectroscopy. The PBI composite membranes containing 1-butyl-3-methylimidazolium-derived ionic liquids exhibited high proton conductivity of 0.098 S·cm−1 at 120 °C when tetrafluoroborate anion was present in the polymeric matrix. This conductivity enhancement might be attributed to the formed hydrogen-bond networks between the IL molecules and the phosphoric acid molecules distributed along the polymeric matrix. Full article
(This article belongs to the Special Issue Polymer Electrolytes for Energy Storage and Conversion Devices)
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13 pages, 2599 KiB  
Article
Optimization of Laccase/Mediator System (LMS) Stage Applied in Fractionation of Eucalyptus globulus
by Javier M. Loaiza, Ascensión Alfaro, Francisco López, María T. García and Juan C. García
Polymers 2019, 11(4), 731; https://doi.org/10.3390/polym11040731 - 22 Apr 2019
Cited by 3 | Viewed by 3304
Abstract
In a biorefinery framework, a laccase/mediator system treatment following autohydrolysis was carried out for eucalyptus wood prior to soda-anthraquinone pulping. The enzymatic and autohydrolysis conditions, with a view to maximizing the extraction of hemicelluloses while preserving the integrity of glucan, were optimized. Secondly, [...] Read more.
In a biorefinery framework, a laccase/mediator system treatment following autohydrolysis was carried out for eucalyptus wood prior to soda-anthraquinone pulping. The enzymatic and autohydrolysis conditions, with a view to maximizing the extraction of hemicelluloses while preserving the integrity of glucan, were optimized. Secondly, pulping of solid phase from Eucalyptus globulus wood autohydrolysis and the enzymatic process was carried out and compared with a conventional soda-anthraquinone (AQ) pulping process. The prehydrolysis and enzymatic delignification of the raw material prior to the delignification with soda- Anthraquinone (AQ) results in paper sheets with a lower kappa number and brightness and strength properties close to conventional soda-AQ paper and a liquid fraction rich in hemicellulose compounds that can be used in additional ways. The advantage of this biorefinery scheme is that it requires a lower concentration of chemical reagents, and lower operating times and temperature in the alkaline delignification stage, which represents an economic and environmental improvement over the conventional process. Full article
(This article belongs to the Special Issue Lignocellulosic Fibers and Films)
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21 pages, 2384 KiB  
Article
Synthesis and Characterization of Dental Nanocomposite Resins Filled with Different Clay Nanoparticles
by Alexandros K. Nikolaidis, Elisabeth A. Koulaouzidou, Christos Gogos and Dimitris S. Achilias
Polymers 2019, 11(4), 730; https://doi.org/10.3390/polym11040730 - 22 Apr 2019
Cited by 38 | Viewed by 5695
Abstract
Nanotechnology comprises a promising approach towards the update of dental materials.The present study focuses on the reinforcement ofdental nanocomposite resins with diverse organomodified montmorillonite (OMMT) nanofillers. The aim is to investigate whether the presence of functional groups in the chemical structure of the [...] Read more.
Nanotechnology comprises a promising approach towards the update of dental materials.The present study focuses on the reinforcement ofdental nanocomposite resins with diverse organomodified montmorillonite (OMMT) nanofillers. The aim is to investigate whether the presence of functional groups in the chemical structure of the nanoclay organic modifier may virtually influence the physicochemical and/or the mechanical attitude of the dental resin nanocomposites. The structure and morphology of the prepared materials were investigated by means of wide angle X-ray diffraction and scanning electron microscopy analysis. Fourier transform infrared spectroscopy was used to determine the variation of the degree of conversion over time. Measurements of polymerization shrinkage and mechanical properties were conducted with a linear variable displacement transducer apparatus and a dynamometer, respectively. All the obtained nanocomposites revealed intercalated structures and most of them had an extensive filler distribution into the polymer matrix. Polymerization kinetics werefound to be influenced by the variance of the clay organomodifier, whilenanoclays with vinyl groups considerably increased the degree of conversion. Polymerization shrinkage was almost limited up to 50% by incorporating nanoclays. The absence of reactive groups in the OMMT structure may retain setting contraction atlow levels. An enhancement of the flexural modulus was observed, mainly by using clay nanoparticles decorated with methacrylated groups, along with a decrease in the flexural strength at a high filler loading. The overall best performance was found for the nanocomposites with OMMTs containing double bonds. The significance of the current work relies on providing novel information about chemical interactions phenomena between nanofillers and the organic matrix towards the improvement of dental restorative materials. Full article
(This article belongs to the Special Issue Polymer Clay Nano-composites)
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17 pages, 5094 KiB  
Article
Structure and Properties of a Metallocene Polypropylene Resin with Low Melting Temperature for Melt Spinning Fiber Application
by Renwei Xu, Peng Zhang, Hai Wang, Xu Chen, Jie Xiong, Jinpeng Su, Peng Chen and Zhicheng Zhang
Polymers 2019, 11(4), 729; https://doi.org/10.3390/polym11040729 - 22 Apr 2019
Cited by 5 | Viewed by 5731
Abstract
An isotactic polypropylene (iPP-1) resin with low melting temperature (Tm) is synthesized by a metallocene catalyst and investigated for melt-spun fiber applications. The structure, thermal and mechanical properties, and feasibility of producing fibers of a commercial metallocene iPP (iPP-2) and [...] Read more.
An isotactic polypropylene (iPP-1) resin with low melting temperature (Tm) is synthesized by a metallocene catalyst and investigated for melt-spun fiber applications. The structure, thermal and mechanical properties, and feasibility of producing fibers of a commercial metallocene iPP (iPP-2) and a conventional Ziegler–Natta iPP (iPP-3) are carefully examined for comparison. Tm of iPP-1 is about 10 °C lower than the other two samples, which is well addressed both in the resin and the fiber products. Besides, the newly developed iPP-1 possesses higher isotacticity and crystallinity than the commercial ones, which assures the mechanical properties of the fiber products. Thanks to the addition of calcium stearate, its crystal grain size is smaller than those of the two other commercial iPPs. iPP-1 shows a similar rheological behavior as the commercial ones and good spinnability within a wide range of take-up speeds (1200–2750 m/min). The tensile property of fibers from iPP-1 is better than commercial ones, which can fulfill the application requirement. The formation of the mesomorphic phase in iPP-1 during melt spinning is confirmed by the orientation and crystallization investigation with wide angle X-ray diffraction (WAXD), which is responsible for its excellent processing capability and the mechanical properties of the resultant fibers. The work may provide not only a promising candidate for the high-performance PP fiber but also a deep understanding of the formation mechanism of the mesomorphic phase during fiber spinning. Full article
(This article belongs to the Special Issue Catalytic Olefin Polymerisation and Polyolefins)
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9 pages, 3184 KiB  
Article
A Bioinspired Functionalization of Polypropylene Separator for Lithium-Sulfur Battery
by Zhijia Zhang, Xuequan Li, Yawen Yan, Wenyi Zhu, Li-Hua Shao and Junsheng Li
Polymers 2019, 11(4), 728; https://doi.org/10.3390/polym11040728 - 22 Apr 2019
Cited by 17 | Viewed by 4900
Abstract
Lithium-sulfur batteries have received intensive attention, due to their high specific capacity, but the shuttle effect of soluble polysulfide results in a decrease in capacity. In response to this issue, we develop a novel tannic acid and Au nanoparticle functionalized separator. The tannic [...] Read more.
Lithium-sulfur batteries have received intensive attention, due to their high specific capacity, but the shuttle effect of soluble polysulfide results in a decrease in capacity. In response to this issue, we develop a novel tannic acid and Au nanoparticle functionalized separator. The tannic acid and gold nanoparticles were modified onto commercial polypropylene separator through a two-step solution process. Due to a large number of phenolic hydroxyl groups contained in the modified layer and the strong polarity of the gold nanoparticles, the soluble polysulfide generated during battery cycling is well stabilized on the cathode side, slowing down the capacity fade brought by the shuttle effect. In addition, the modification effectively improves the electrolyte affinity of the separator. As a result of these benefits, the novel separator exhibits improved battery performance compared to the pristine polypropylene separator. Full article
(This article belongs to the Special Issue Polymer Based Catalysts and Membranes and Their Composites for Energy Storage and Conversion Applications)
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12 pages, 2836 KiB  
Article
PA12 Powder Recycled from SLS for FDM
by Li Feng, Yan Wang and Qinya Wei
Polymers 2019, 11(4), 727; https://doi.org/10.3390/polym11040727 - 22 Apr 2019
Cited by 67 | Viewed by 9039
Abstract
In this study, Polyamide 12 (PA12) powder recycled after selective laser sintering (SLS) was made into filaments for fused deposition modelling (FDM). Compared with fresh PA12, the melt flow rate (MFR) of the recycled PA12 powder decreased by 77%, but the mechanical properties [...] Read more.
In this study, Polyamide 12 (PA12) powder recycled after selective laser sintering (SLS) was made into filaments for fused deposition modelling (FDM). Compared with fresh PA12, the melt flow rate (MFR) of the recycled PA12 powder decreased by 77%, but the mechanical properties were only slightly reduced. In FDM, the printing speed and building orientation were changed, and the performance of the printed parts was tested. If the printing speed is too fast or too slow, the mechanical properties of the parts will be affected, and there is an optimal speed range. The tensile strength, flexural modulus, and impact strength of a printed test sample made from recycled powder reached 95%, 85%, and 87% of an x-direction test sample made from fresh PA12, respectively. For test samples printed from different orientations, the mechanical properties of the test samples printed in the x-direction were the best, while the crystallization performance was the opposite. Scanning electron microscope (SEM) images show that the printed test sample had good compactness and mechanical properties, and the delamination phenomenon was basically not observed. Full article
(This article belongs to the Special Issue Additive Manufacturing of Polymeric Materials)
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41 pages, 6258 KiB  
Review
Nanomaterials in Advanced, High-Performance Aerogel Composites: A Review
by Elizabeth Barrios, David Fox, Yuen Yee Li Sip, Ruginn Catarata, Jean E. Calderon, Nilab Azim, Sajia Afrin, Zeyang Zhang and Lei Zhai
Polymers 2019, 11(4), 726; https://doi.org/10.3390/polym11040726 - 20 Apr 2019
Cited by 124 | Viewed by 17303
Abstract
Aerogels are one of the most interesting materials of the 21st century owing to their high porosity, low density, and large available surface area. Historically, aerogels have been used for highly efficient insulation and niche applications, such as interstellar particle capture. Recently, aerogels [...] Read more.
Aerogels are one of the most interesting materials of the 21st century owing to their high porosity, low density, and large available surface area. Historically, aerogels have been used for highly efficient insulation and niche applications, such as interstellar particle capture. Recently, aerogels have made their way into the composite universe. By coupling nanomaterial with a variety of matrix materials, lightweight, high-performance composite aerogels have been developed for applications ranging from lithium-ion batteries to tissue engineering materials. In this paper, the current status of aerogel composites based on nanomaterials is reviewed and their application in environmental remediation, energy storage, controlled drug delivery, tissue engineering, and biosensing are discussed. Full article
(This article belongs to the Special Issue Polymer and Composite Aerogels)
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8 pages, 488 KiB  
Article
NMR Analysis of Poly(Lactic Acid) via Statistical Models
by Koto Suganuma, Tetsuo Asakura, Miyuki Oshimura, Tomohiro Hirano, Koichi Ute and H. N. Cheng
Polymers 2019, 11(4), 725; https://doi.org/10.3390/polym11040725 - 19 Apr 2019
Cited by 20 | Viewed by 7310
Abstract
The physical properties of poly(lactic acid) (PLA) are influenced by its stereoregularity and stereosequence distribution, and its polymer stereochemistry can be effectively studied by NMR spectroscopy. In previously published NMR studies of PLA tacticity, the NMR data were fitted to pair-addition Bernoullian models. [...] Read more.
The physical properties of poly(lactic acid) (PLA) are influenced by its stereoregularity and stereosequence distribution, and its polymer stereochemistry can be effectively studied by NMR spectroscopy. In previously published NMR studies of PLA tacticity, the NMR data were fitted to pair-addition Bernoullian models. In this work, we prepared several PLA samples with a tin catalyst at different L,L-lactide and D,D-lactide ratios. Upon analysis of the tetrad intensities with the pair-addition Bernoullian model, we found substantial deviations between observed and calculated intensities due to the presence of transesterification and racemization during the polymerization processes. We formulated a two-state (pair-addition Bernoullian and single-addition Bernoullian) model, and it gave a better fit to the observed data. The use of the two-state model provides a quantitative measure of the extent of transesterification and racemization, and potentially yields useful information on the polymerization mechanism. Full article
(This article belongs to the Special Issue NMR in Polymer Science)
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2 pages, 651 KiB  
Erratum
Erratum: Electrostatic-Interaction-Driven Assembly of Binary Hybrids towards Fire-Safe Epoxy Resin Nanocomposites. Polymers 2019, 11, 229.
by Lu Liu, Wei Wang, Yongqian Shi, Libi Fu, Lulu Xu and Bin Yu
Polymers 2019, 11(4), 724; https://doi.org/10.3390/polym11040724 - 19 Apr 2019
Cited by 1 | Viewed by 2381
Abstract
The authors wish to make a change to the published paper [...] Full article
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13 pages, 3264 KiB  
Article
Improved Aging Stability of Ethylene-Norbornene Composites Filled with Lawsone-Based Hybrid Pigment
by Anna Marzec and Bolesław Szadkowski
Polymers 2019, 11(4), 723; https://doi.org/10.3390/polym11040723 - 19 Apr 2019
Cited by 18 | Viewed by 4232
Abstract
In this study, we produced a new organic-inorganic hybrid pigment based on a natural chromophore. Lawsone was selected as the active organic compound and incorporated into aluminum-magnesium hydroxycarbonate (LH). The hydroxynaphthoquinone derivative lawsone (Lawsonia inermis L.) is a naturally occurring dye, [...] Read more.
In this study, we produced a new organic-inorganic hybrid pigment based on a natural chromophore. Lawsone was selected as the active organic compound and incorporated into aluminum-magnesium hydroxycarbonate (LH). The hydroxynaphthoquinone derivative lawsone (Lawsonia inermis L.) is a naturally occurring dye, which is commonly used as a colorant because of its nontoxicity and biological functions. The structure and stability of the hybrid colorant were investigated using 27-Al solid-state nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), secondary ion mass spectrometry (TOF-SIMS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and UV-Vis spectroscopy. TOF-SIMS and 27Al NMR spectroscopy revealed interactions between the dye molecules and metal ions present in the LH host, confirming successful formation of an LH-based hybrid (LH/lawsone). In the next part of the study, we examined the effect of the hybrid pigment on the mechanical and thermal properties of ethylene-norbornene (EN) materials, as well as the aging resistance of the colored composites to irradiation across the full solar spectrum. Dynamic mechanical analysis (DMA) and the results of tensile break tests revealed that the EN+LH/lawsone composite had significantly better resistance to solar irradiation in comparison to EN and EN with an unmodified carrier. Full article
(This article belongs to the Special Issue Eurofillers Polymer Blends)
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11 pages, 2268 KiB  
Article
Preparation and Characterization of Whey Protein-Based Polymers Produced from Residual Dairy Streams
by Bushra Chalermthai, Wui Yarn Chan, Juan-Rodrigo Bastidas-Oyanedel, Hanifa Taher, Bradley D. Olsen and Jens Ejbye Schmidt
Polymers 2019, 11(4), 722; https://doi.org/10.3390/polym11040722 - 19 Apr 2019
Cited by 28 | Viewed by 8310
Abstract
The wide use of non-biodegradable, petroleum-based plastics raises important environmental concerns, which urges finding alternatives. In this study, an alternative way to produce polymers from a renewable source—milk proteins—was investigated with the aim of replacing polyethylene. Whey protein can be obtained from whey [...] Read more.
The wide use of non-biodegradable, petroleum-based plastics raises important environmental concerns, which urges finding alternatives. In this study, an alternative way to produce polymers from a renewable source—milk proteins—was investigated with the aim of replacing polyethylene. Whey protein can be obtained from whey residual, which is a by-product in the cheese-making process. Two different sources of whey protein were tested: Whey protein isolate (WPI) containing 91% protein concentration and whey protein concentrate (WPC) containing 77% protein concentration. These were methacrylated, followed by free radical polymerization with co-polymer poly(ethylene glycol) methyl ether methacrylate (PEGMA) to obtain polymer sheets. Different protein concentrations in water (11–14 w/v%), at two protein/PEGMA mass-ratios, 20:80 and 30:70, were tested. The polymers made from WPI and WPC at a higher protein/PEGMA ratio of 30:70 had significantly better tensile strength than the one with lower protein content, by about 1–2 MPa (the best 30:70 sample exhibited 3.8 ± 0.2 MPa and the best 20:80 sample exhibited 1.9 ± 0.4 MPa). This indicates that the ratio between the hard (protein) and soft (copolymer PEGMA) domains induce significant changes to the tensile strengths of the polymer sheets. Thermally, the WPI-based polymer samples are stable up to 277.8 ± 6.2 °C and the WPC-based samples are stable up to 273.0 ± 3.4 °C. Full article
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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20 pages, 4725 KiB  
Article
Synthesis and Characterization of Clay Polymer Nanocomposites of P(4VP-co-AAm) and Their Application for the Removal of Atrazine
by Jorge A. Ramírez-Gómez, Javier Illescas, María del Carmen Díaz-Nava, Claudia Muro-Urista, Sonia Martínez-Gallegos and Ernesto Rivera
Polymers 2019, 11(4), 721; https://doi.org/10.3390/polym11040721 - 19 Apr 2019
Cited by 10 | Viewed by 3909
Abstract
Atrazine (ATZ) is an herbicide which is applied to the soil, and its mechanism of action involves the inhibition of photosynthesis. One of its main functions is to control the appearance of weeds in crops, primarily in corn, sorghum, sugar cane, and wheat; [...] Read more.
Atrazine (ATZ) is an herbicide which is applied to the soil, and its mechanism of action involves the inhibition of photosynthesis. One of its main functions is to control the appearance of weeds in crops, primarily in corn, sorghum, sugar cane, and wheat; however, it is very toxic for numerous species, including humans. Therefore, this work deals with the adsorption of ATZ from aqueous solutions using nanocomposite materials, synthesized with two different types of organo-modified clays. Those were obtained by the free radical polymerization of 4-vinylpyridine (4VP) and acrylamide (AAm) in different stoichiometric ratios, using tetrabutylphosphonium persulfate (TBPPS) as a radical initiator and N,N′-methylenebisacrylamide (BIS) as cross-linking agent. The structural, morphological, and textural characteristics of clays, copolymers, and nanocomposites were determined through different analytical and instrumental techniques, i.e., X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). Adsorption kinetics experiments of ATZ were determined with the modified and synthesized materials, and the effect of the ratio between 4VP and AAm moieties on the removal capacities of the obtained nanocomposites was evaluated. Finally, from these sets of experiments, it was demonstrated that the synthesized nanocomposites with higher molar fractions of 4VP obtained the highest removal percentages of ATZ. Full article
(This article belongs to the Special Issue Polymer Clay Nano-composites)
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15 pages, 5080 KiB  
Article
Preparation and Characteristics of an Environmentally Friendly Hyperbranched Flame-Retardant Polyurethane Hybrid Containing Nitrogen, Phosphorus, and Silicon
by Chin-Hsing Chen and Chin-Lung Chiang
Polymers 2019, 11(4), 720; https://doi.org/10.3390/polym11040720 - 19 Apr 2019
Cited by 22 | Viewed by 4850
Abstract
The NCO functional group of 3-isocyanatoproplytriethoxysilane (IPTS) and the OH functional group of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phospha-phenantbrene-10-oxide (DOPO-BQ) were used to conduct an addition reaction. Following completion of the reaction, triglycidyl isocyanurate (TGIC) was introduced to conduct a ring-opening reaction. Subsequently, a sol–gel method was used [...] Read more.
The NCO functional group of 3-isocyanatoproplytriethoxysilane (IPTS) and the OH functional group of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phospha-phenantbrene-10-oxide (DOPO-BQ) were used to conduct an addition reaction. Following completion of the reaction, triglycidyl isocyanurate (TGIC) was introduced to conduct a ring-opening reaction. Subsequently, a sol–gel method was used to initiate a hydrolysis–condensation reaction on TGIC–IPTS–DOPO-BQ to form a hyperbranched nitrogen–phosphorous–silicon (HBNPSi) flame retardant. This flame retardant was incorporated into a polyurethane (PU) matrix to prepare a hybrid material. Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), limiting oxygen index (LOI), UV-VIS spectrophotometry, and Raman analysis were conducted to characterize the structure and analyze the transparency, thermal stability, flame retardancy, and residual char to understand the flame retardant mechanism of the prepared hybrid material. After the flame retardant was added, the maximum degradation rate decreased from −36 to −17 wt.%/min, the integral procedural decomposition temperature (IPDT) increased from 348 to 488 °C, and the char yield increased from 0.7 to 8.1 wt.%. The aforementioned results verified that the thermal stability of PU can be improved after adding HBNPSi. The LOI analysis indicated that the pristine PU was flammable because the LOI of pristine PU was only 19. When the content of added HBNPSi was 40%, the LOI value was 26; thus the PU hybrid became nonflammable. Full article
(This article belongs to the Special Issue Thermal Insulating and Fire-Resistant Polymer Composites)
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13 pages, 3540 KiB  
Article
Enhancing Saltiness Perception Using Chitin Nanomaterials
by Wan-Chen Tsai, Shang-Ta Wang, Ke-Liang Bruce Chang and Min-Lang Tsai
Polymers 2019, 11(4), 719; https://doi.org/10.3390/polym11040719 - 19 Apr 2019
Cited by 31 | Viewed by 4733
Abstract
In the present study, we prepared and characterized chitin nanomaterials with different diameters, lengths, and degree of deacetylation (DD), and investigated their capability for enhancing saltiness perception. Chitin was isolated from squid pens and transformed into chitin nanofiber (CNF), deacetylated chitin nanofiber (DACNF), [...] Read more.
In the present study, we prepared and characterized chitin nanomaterials with different diameters, lengths, and degree of deacetylation (DD), and investigated their capability for enhancing saltiness perception. Chitin was isolated from squid pens and transformed into chitin nanofiber (CNF), deacetylated chitin nanofiber (DACNF), and chitin nanocrystal (CNC) by ultrasonication, alkali treatment followed by ultrasonication and acid hydrolysis, respectively. The diameters of CNF, CNC and DACNF were 17.24 nm, 16.05 nm and 15.01 nm while the lengths were 1725.05 nm, 116.91 nm, and 1806.60 nm, respectively. The aspect ratios of CNF and DACNF were much higher than that of CNC. The crystalline indices of CNF and CNC were lower than that of original β-chitin, suggesting that ultrasonication and acid hydrolysis might change the molecular arrangement in crystalline region of chitin. The zeta-potentials were between 19.73 nV and 30.08 mV of chitin nanomaterials in distilled water. Concentrations of chitin nanomaterials (40–74 μg/mL) showed minimal effect on zeta-potential, whereas increasing the level of NaCl reduced the zeta-potential of solution. Moreover, NaCl solution (0.3%) with chitin nanomaterials addition produced significant higher saltiness perception than that of solution with NaCl alone. Therefore, chitin nanomaterials may be promising saltiness enhancers in the food industry. Full article
(This article belongs to the Special Issue Modifications and Applications of Chitin/Chitosan for Biomedical, Pharmaceutical, Cosmetic, Biotechnology and Related Applications)
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20 pages, 5042 KiB  
Article
The Use of Lanthanum Ions and Chitosan for Boron Elimination from Aqueous Solutions
by Joanna Kluczka, Gabriela Dudek, Alicja Kazek-Kęsik, Małgorzata Gnus, Maciej Krzywiecki, Krzysztof Mitko and Katarzyna Krukiewicz
Polymers 2019, 11(4), 718; https://doi.org/10.3390/polym11040718 - 19 Apr 2019
Cited by 9 | Viewed by 4690
Abstract
Boron is an essential element for plants and living organisms; however, it can be harmful if its concentration in the environment is too high. In this paper, lanthanum(III) ions were introduced to the structure of chitosan via an encapsulation technique and the obtained [...] Read more.
Boron is an essential element for plants and living organisms; however, it can be harmful if its concentration in the environment is too high. In this paper, lanthanum(III) ions were introduced to the structure of chitosan via an encapsulation technique and the obtained hydrogel (La-CTS) was used for the elimination of the excess of B(III) from modelling solutions. The reaction between boric acid and hydroxyl groups bound to the lanthanum coordinated by chitosan active centres was the preponderant mechanism of the bio-adsorption removal process. The results demonstrated that La-CTS removed boric acid from the aqueous solution more efficiently than either lanthanum hydroxide or native chitosan hydrogel, respectively. When the initial boron concentration was 100 mg/dm3, the maximum adsorption capacity of 11.1 ± 0.3 mg/g was achieved at pH 5 and the adsorption time of 24 h. The successful introduction of La(III) ions to the chitosan backbone was confirmed by Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy, Fourier-Transform Infrared Spectroscopy, X-Ray Diffraction, X-ray Photoelectron Spectroscopy, and Inductively Coupled Plasma Optical Emission Spectroscopy. Due to its high-performance boron adsorption-desorption cycle and convenient form, La-CTS seems to be a promising bio-adsorbent for water treatment. Full article
(This article belongs to the Special Issue Chitin and Chitosan: Properties and Applications)
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13 pages, 4236 KiB  
Article
Manifestation of Interactions of Nano-Silica in Silicone Rubber Investigated by Low-Frequency Dielectric Spectroscopy and Mechanical Tests
by Chao Wu, Yanfeng Gao, Xidong Liang, Stanislaw M. Gubanski, Qian Wang, Weining Bao and Shaohua Li
Polymers 2019, 11(4), 717; https://doi.org/10.3390/polym11040717 - 19 Apr 2019
Cited by 30 | Viewed by 5238
Abstract
Silicone rubber composites filled with nano-silica are currently widely used as high voltage insulating materials in power transmission and substation systems. We present a systematic study on the dielectric and mechanical performance of silicone rubber filled with surface modified and unmodified fumed nano-silica. [...] Read more.
Silicone rubber composites filled with nano-silica are currently widely used as high voltage insulating materials in power transmission and substation systems. We present a systematic study on the dielectric and mechanical performance of silicone rubber filled with surface modified and unmodified fumed nano-silica. The results indicate that the different interfaces between the silicone rubber and the two types of nano-silica introduce changes in their dielectric response when electrically stressed by a sinusoidal excitation in the frequency range of 10−4–1 Hz. The responses of pure silicone rubber and the composite filled with modified silica can be characterized by a paralleled combination of Maxwell-Wagner-Sillars interface polarization and DC conduction. In contrast, the silicone rubber composite with the unmodified nano-silica exhibits a quasi-DC (Q-DC) transport process. The mechanical properties of the composites (represented by their stress-strain characteristics) reveal an improvement in the mechanical strength with increasing filler content. Moreover, the strain level of the composite with a modified filler is improved. Full article
(This article belongs to the Collection Silicon-Containing Polymeric Materials)
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13 pages, 3732 KiB  
Article
Preparation of Hydrogel/Silver Nanohybrids Mediated by Tunable-Size Silver Nanoparticles for Potential Antibacterial Applications
by Yeray A. Rodríguez Nuñez, Ricardo I. Castro, Felipe A. Arenas, Zoraya E. López-Cabaña, Gustavo Carreño, Verónica Carrasco-Sánchez, Adolfo Marican, Jorge Villaseñor, Esteban Vargas, Leonardo S. Santos and Esteban F. Durán-Lara
Polymers 2019, 11(4), 716; https://doi.org/10.3390/polym11040716 - 19 Apr 2019
Cited by 36 | Viewed by 6640
Abstract
In this study, a versatile synthesis of silver nanoparticles of well-defined size by using hydrogels as a template and stabilizer of nanoparticle size is reported. The prepared hydrogels are based on polyvinyl alcohol and maleic acid as crosslinker agents. Three hydrogels with the [...] Read more.
In this study, a versatile synthesis of silver nanoparticles of well-defined size by using hydrogels as a template and stabilizer of nanoparticle size is reported. The prepared hydrogels are based on polyvinyl alcohol and maleic acid as crosslinker agents. Three hydrogels with the same nature were synthesized, however, the crosslinking degree was varied. The silver nanoparticles were synthesized into each prepared hydrogel matrix achieving three significant, different-sized nanoparticles that were spherical in shape with a narrow size distribution. It is likely that the polymer network stabilized the nanoparticles. It was determined that the hydrogel network structure can control the size and shape of the nanoparticles. The hydrogel/silver nanohybrids were characterized by swelling degree, Thermal Gravimetric Analysis (TGA), Fourier Transform Infrared (FT-IR), Scanning Electron Microscopy (SEM) and Transmission Electron Microscope (TEM). Antibacterial activity against Staphylococcus aureus was evaluated, confirming antimicrobial action of the encapsulated silver nanoparticles into the hydrogels. Full article
(This article belongs to the Special Issue Hydrogels and Gels for Biomedical and Sustainable Applications)
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