Polymers

13 pages, 3125 KiB

Open AccessArticle

Effect of High Molecular Weight PPTA on Liquid Crystalline Phase and Spinning Process of Aramid Fibers

by Cuiqing Teng, Hui Li, Jing Liu, Hao Gu, Haijuan Kong and Muhuo Yu

Polymers 2020, 12(5), 1206; https://doi.org/10.3390/polym12051206 - 25 May 2020

Cited by 18 | Viewed by 6560

High molecular weight poly (p-phenylene-terephthalamide) (h-PPTA) was blended with the commercial PPTA in concentrated sulfuric acid to improve the spinnability of the polymer solutions and the mechanical properties of the as-spun fibers. h-PPTA in the solution has an influence on the [...] Read more.

High molecular weight poly (p-phenylene-terephthalamide) (h-PPTA) was blended with the commercial PPTA in concentrated sulfuric acid to improve the spinnability of the polymer solutions and the mechanical properties of the as-spun fibers. h-PPTA in the solution has an influence on the temperature of the formation of liquid crystalline phenomenon. The temperature range with the existence of the liquid crystalline phase increases upon the contents of h-PPTA in the solution, and the extended temperature window is helpful for the preparation of PPTA fibers by the dry-jet wet-spinning technology. The long-chains of h-PPTA enhance the inter-macromolecular interactions and induce the orientation of short-chains for PPTA along the fiber axis under the shear stress in the spinneret and the stretching stress at the air gap. These effects also increase the maximum drawing ratio in the spinning process and improve the mechanical properties of the obtained fibers. The crystallinity and crystal orientation of the fibers are investigated by X-ray diffraction, and results from sonic velocity test further confirm ordering state of the macromolecular chains. The fibril morphologies of the fibers are also studied by a scanning electric microscope. Full article

(This article belongs to the Section Polymer Processing and Engineering)

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17 pages, 1706 KiB

Open AccessReview

The Effect of Chitosan on the Chemical Structure, Morphology, and Selected Properties of Polyurethane/Chitosan Composites

by Agnieszka Piotrowska-Kirschling and Joanna Brzeska

Polymers 2020, 12(5), 1205; https://doi.org/10.3390/polym12051205 - 25 May 2020

Cited by 25 | Viewed by 7290

Abstract

Materials science is an interdisciplinary area of studies. This science focuses on the influence of the physico-chemical properties of materials on their application in human everyday lives. The materials’ synthesis should be developed in accordance with sustainable development. Polyurethanes (PUR) represent a significant [...] Read more.

Materials science is an interdisciplinary area of studies. This science focuses on the influence of the physico-chemical properties of materials on their application in human everyday lives. The materials’ synthesis should be developed in accordance with sustainable development. Polyurethanes (PUR) represent a significant consumption of plastic in the world. Modification of PUR, e.g., with polysaccharide of natural origin (chitosan, Chit), should have a positive effect on their functional properties and degradability in the natural environment. The basic parameters affecting the scope and direction of changes are the size and quantity of the chitosan particles. The impact assessment of chitosan on the chemical structure, morphology, thermal properties, crystallinity, mechanical properties, flammability, water sorption, adsorption properties, degradability, and biological activity of PUR/Chit composites (without other additives) is discussed in this article. To the best of our knowledge, recent literature does not contain a study discussing the direct impact of the presence of chitosan in the structure of PUR/Chit composite on its properties, regardless of the intended uses. This paper provides an overview of publications, which presents the results of a study on the effect of adding chitosan in polyurethane/chitosan composites without other additives on the properties of polyurethane. Full article

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18 pages, 3381 KiB

Open AccessArticle

Reclaimed Rubber/Poly(ε-caprolactone) Blends: Structure, Mechanical, and Thermal Properties

by Aleksander Hejna, Łukasz Zedler, Marta Przybysz-Romatowska, Javier Cañavate, Xavier Colom and Krzysztof Formela

Polymers 2020, 12(5), 1204; https://doi.org/10.3390/polym12051204 - 25 May 2020

Cited by 13 | Viewed by 4471

Abstract

The amount of elastomeric waste, especially from tires is constantly increasing on a global scale. The recycling of these residua should be considered a priority. Compounding the waste rubbers with other polymers can be an excellent alternative to reuse waste materials. This procedure [...] Read more.

The amount of elastomeric waste, especially from tires is constantly increasing on a global scale. The recycling of these residua should be considered a priority. Compounding the waste rubbers with other polymers can be an excellent alternative to reuse waste materials. This procedure requires solving the issue of the lack of compatibility between the waste rubber particles and other polymers. Simultaneously, there is a claim for introducing biodegradable plastics materials to reduce their environmental impact. In this work, reclaimed rubber/poly(ε-caprolactone) (RR/PCL) blends are proposed to enhance the recycling and upcycling possibilities of waste rubbers. The results show that the addition of PCL to the RR allows obtaining blends with improved mechanical properties, good thermal stability, and enhanced interfacial compatibility between the used components. Structure and properties of the proposed RR/PCL have been studied by means of static and dynamic mechanical testing, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA)-FTIR analysis. Full article

(This article belongs to the Special Issue Environmentally-Friendly Polymeric Materials Based on Recycling and Bio-Based Components)

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12 pages, 3110 KiB

Open AccessArticle

A Novel Synthesis of Poly(Ester-Alt-Selenide)s by Ring-Opening Copolymerization of γ-Selenobutyrolactone and Epoxy Monomer

by Ya’nan Wang, Xiaofang Lin, Zhengbiao Zhang, Jian Zhu, Xiangqiang Pan and Xiulin Zhu

Polymers 2020, 12(5), 1203; https://doi.org/10.3390/polym12051203 - 25 May 2020

Cited by 9 | Viewed by 3400

Abstract

Ring-opening copolymerization (ROCOP) is an effective means to prepare functionalized polyester. In this work, a type of selenide-containing polyesters with controllable structure, molecular weight, and molecular weight distribution was successfully prepared by ROCOP of γ-selenobutyrolactone and epoxy compounds. The influence of the catalyst, [...] Read more.

Ring-opening copolymerization (ROCOP) is an effective means to prepare functionalized polyester. In this work, a type of selenide-containing polyesters with controllable structure, molecular weight, and molecular weight distribution was successfully prepared by ROCOP of γ-selenobutyrolactone and epoxy compounds. The influence of the catalyst, solvent, and reaction temperature on the reaction efficiency was examined. Then, kinetic study was investigated under an optimized condition. The structure of the copolymers was carefully characterized by nuclear magnetic resonance (NMR), ¹H NMR, ¹³C NMR, and ⁷⁷Se NMR, Matrix-assisted laser-desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS), and size exclusion chromatography (SEC). The resulting polymers showed a linear structure with a sequence regulated backbone repeating unit of ester-selenide. On this basis, some typical epoxides were investigated to verify the scope of the polymerization system. Due to the “living”/controlled characteristics of this ROCOP, multiblock, amphiphilic, and stereotactic copolymers could be prepared with a pre-designed structure. As expected, the selenide-containing amphiphilic copolymer could self-assemble to micelles and showed an oxidative response. Full article

(This article belongs to the Section Polymer Chemistry)

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15 pages, 3797 KiB

Open AccessArticle

A Flame-Retardant Phytic-Acid-Based LbL-Coating for Cotton Using Polyvinylamine

by Olga Zilke, Dennis Plohl, Klaus Opwis, Thomas Mayer-Gall and Jochen Stefan Gutmann

Polymers 2020, 12(5), 1202; https://doi.org/10.3390/polym12051202 - 25 May 2020

Cited by 37 | Viewed by 5130

Abstract

Phytic acid (PA), as a natural source of phosphorus, was immobilized on cotton (CO) in a layer-by-layer (LbL) approach with polyvinylamine (PVAm) as the oppositely charged electrolyte to create a partly bio-based flame-retardant finish. PVAm was employed as a synthetic nitrogen source with [...] Read more.

Phytic acid (PA), as a natural source of phosphorus, was immobilized on cotton (CO) in a layer-by-layer (LbL) approach with polyvinylamine (PVAm) as the oppositely charged electrolyte to create a partly bio-based flame-retardant finish. PVAm was employed as a synthetic nitrogen source with the highest density of amine groups of all polymers. Vertical flame tests revealed a flame-retardant behavior with no afterflame and afterglow time for a coating of 15 bilayers (BL) containing 2% phosphorus and 1.4% nitrogen. The coating achieved a molar P:N ratio of 3:5. Microscale combustion calorimetry (MCC) analyses affirmed the flame test findings by a decrease in peak heat release rate (pkHRR) by more than 60% relative to unfinished CO. Thermogravimetric analyses (TGA) and MCC measurements exhibited a shifted CO peak to lower temperatures indicating proceeding reactions to form an isolating char on the surface. Fourier transform infrared spectroscopy (FTIR) coupled online with a TGA system, allowed the identification of a decreased amount of acrolein, methanol, carbon monoxide and formaldehyde during sample pyrolysis and a higher amount of released water. Thereby the toxicity of released volatiles was reduced. Our results prove that PA enables a different reaction by catalyzing cellulosic dehydration, which results in the formation of a protective char on the surface of the burned fabric. Full article

(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials II- Bio-Inspired and Environmentally-Benign Formulations and Methods)

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22 pages, 4058 KiB

Open AccessArticle

Doxycycline and Zinc Loaded Silica-Nanofibrous Polymers as Biomaterials for Bone Regeneration

by Manuel Toledano, Manuel Toledano-Osorio, Raquel Osorio, Álvaro Carrasco-Carmona, José-Luis Gutiérrez-Pérez, Aida Gutiérrez-Corrales, María-Angeles Serrera-Figallo, Christopher D. Lynch and Daniel Torres-Lagares

Polymers 2020, 12(5), 1201; https://doi.org/10.3390/polym12051201 - 25 May 2020

Cited by 26 | Viewed by 4068

Abstract

The main target of bone tissue engineering is to design biomaterials that support bone regeneration and vascularization. Nanostructured membranes of (MMA)₁-co-(HEMA)₁/(MA)₃-co-(HEA)₂ loaded with 5% wt of SiO₂-nanoparticles (HOOC-Si-Membrane) were doped with zinc (Zn-HOOC-Si-Membrane) or [...] Read more.

The main target of bone tissue engineering is to design biomaterials that support bone regeneration and vascularization. Nanostructured membranes of (MMA)₁-co-(HEMA)₁/(MA)₃-co-(HEA)₂ loaded with 5% wt of SiO₂-nanoparticles (HOOC-Si-Membrane) were doped with zinc (Zn-HOOC-Si-Membrane) or doxycycline (Dox-HOOC-Si-Membrane). Critical bone defects were effectuated on six New Zealand-bred rabbit skulls and covered with the membranes. After six weeks, the bone architecture was evaluated with micro computed tomography. Three histological analyses were utilized to analyse bone regeneration, including von Kossa silver nitrate, toluidine blue and fluorescence. All membrane-treated defects exhibited higher number of osteocytes and bone perimeter than the control group without the membrane. Zn-HOOC-Si-Membranes induced higher new bone and osteoid area than those treated with HOOC-Si-Membranes, and control group, respectively. Zn-HOOC-Si-Membranes and Dox-HOOC-Si-Membranes attained the lowest ratio M1 macrophages/M2 macrophages. Dox-HOOC-Si-Membranes caused the lowest number of osteoclasts, and bone density. At the trabecular new bone, Zn-HOOC-Si-Membranes produced the highest angiogenesis, bone thickness, connectivity, junctions and branches. Zn-HOOC-Si-Membranes enhanced biological activity, attained a balanced remodeling, and achieved the greatest regenerative efficiency after osteogenesis and angiogenesis assessments. The bone-integrated Zn-HOOC-Si-Membranes can be considered as bioactive modulators provoking a M2 macrophages (pro-healing cells) increase, being a potential biomaterial for promoting bone repair. Full article

(This article belongs to the Special Issue Polymeric Materials for Dental Applications)

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14 pages, 2393 KiB

Open AccessArticle

Prevention of Secondary Caries Using Resin-Based Pit and Fissure Sealants Containing Hydrated Calcium Silicate

by Song-Yi Yang, Ji-Won Choi, Kwang-Mahn Kim and Jae-Sung Kwon

Polymers 2020, 12(5), 1200; https://doi.org/10.3390/polym12051200 - 25 May 2020

Cited by 21 | Viewed by 3868

Abstract

The objective of this study was to investigate the effects of hydrated calcium silicate filler (hCS) on resin-based pit and fissure sealants’ acid neutralization, calcium ion release, and mechanical and physical properties. To produce the hCS filler, Portland cement (CS) was mixed with [...] Read more.

The objective of this study was to investigate the effects of hydrated calcium silicate filler (hCS) on resin-based pit and fissure sealants’ acid neutralization, calcium ion release, and mechanical and physical properties. To produce the hCS filler, Portland cement (CS) was mixed with distilled water and ground into fine particles. The particles were then mixed with silanized glass filler and added to a photo-activated resin matrix. To evaluate the acid neutralization and calcium ion release properties, the specimens were immersed in a pH 4.0 lactic acid solution and distilled water for 28 days. Also, the flexural strength, depth of cure, water sorption, and solubility were tested. All of the groups containing hCS and CS required less than one minute to increase the pH from 4.0 to 5.5. With 50% hCS, the calcium ion release was higher than 50% CS in the distilled water at the initial time. The flexural strength and depth of cure decreased according to the increasing proportion of hCS added. The water sorption and solubility had an increasing trend as increasing proportions of hCS were added. These findings showed that pit and fissure sealant containing hCS exhibit superior acid neutralization and calcium release properties, and may be promising for caries-inhibiting dental material. Full article

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13 pages, 3738 KiB

Open AccessArticle

Curing Behaviors of Alkynyl-Terminated Copolyether with Glycidyl Azide Polymer in Energetic Plasticizers

by Jinghui Hu, Yina Liu, Kun Cong, Jiyu He and Rongjie Yang

Polymers 2020, 12(5), 1199; https://doi.org/10.3390/polym12051199 - 25 May 2020

Cited by 15 | Viewed by 3135

Abstract

Alkynyl-terminated polyethylene oxide−tetrahydrofuran (ATPET) and glycidyl azide polymer (GAP) could be linked through click-chemistry between the alkynyl and azide, and the product may serve a binder for solid propellants. The effects of the energetic plasticizers A3 [1:1 mixture of bis-(2,2-dinitropropy) acetal (BDNPA) and [...] Read more.

Alkynyl-terminated polyethylene oxide−tetrahydrofuran (ATPET) and glycidyl azide polymer (GAP) could be linked through click-chemistry between the alkynyl and azide, and the product may serve a binder for solid propellants. The effects of the energetic plasticizers A3 [1:1 mixture of bis-(2,2-dinitropropy) acetal (BDNPA) and bis-(2,2-dinitropropyl) formal(BDNPN)] and Bu-NENA [N-butyl-N-(2nitroxyethyl) nitramine] on the curing reaction between ATPET and GAP have been studied. A diffusion-ordered nuclear magnetic resonance spectroscopy (DOSY-NMR) approach has been used to monitor the change in the diffusion coefficient of cross-linked polytriazole polyethylene oxide−tetrahydrofuran (PTPET). The change in the diffusion coefficient of PTPET with A3 plasticizer is significantly higher than that of PTPET with Bu-NENA. Viscosity analysis further highlighted the difference between A3 and Bu-NENA in the curing process—the curing curve of PTPET (A3) with time can be divided into two stages, with an inflection point being observed on the fourth day. For PTPET (Bu-NENA), in contrast, only one stage is seen. The above methods, together with gel permeation chromatography (GPC) analysis, revealed distinct effects of A3 and Bu-NENA on the curing process of PTPET. X-ray Photoelectron Spectroscopy (XPS) analysis showed that Bu-NENA has little effect on the valence oxidation of copper in the catalyst. Thermogravimetric (TG) analysis indicated that Bu-NENA helps to improve the thermal stability of the catalyst. After analysis of several possible factors by means of XPS, modeling with Material Studio and TG, the formation of molecular cages between Bu-NENA and copper is considered to be the reason for the above differences. In this article, GAP (Mn = 4000 g/mol) was used to replace GAP (Mn = 427 g/mol) to successfully synthesize the PTPET elastomer with Bu-NENA plasticizer. Mechanical data measured for the PTPET (Bu-NENA) sample included ε = 34.26 ± 2.98%, and σ = 0.198 ± 0.015 MPa. Full article

(This article belongs to the Special Issue Polymer Matrix Composites for Advanced Applications II)

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15 pages, 1245 KiB

Open AccessArticle

The Synergistic Microbiological Effects of Industrial Produced Packaging Polyethylene Films Incorporated with Zinc Nanoparticles

by Szymon Mania, Mateusz Cieślik, Marcin Konzorski, Paweł Święcikowski, Andrzej Nelson, Adrianna Banach and Robert Tylingo

Polymers 2020, 12(5), 1198; https://doi.org/10.3390/polym12051198 - 25 May 2020

Cited by 18 | Viewed by 4186

Abstract

Zinc compounds in polyolefin films regulate the transmission of UV-VIS radiation, affect mechanical properties and antimicrobial activity. According to hypothesis, the use of zinc- containing masterbatches in polyethylene films (PE) with different chemical nature—hydrophilic zinc oxide (ZO) and hydrophobic zinc stearate (ZS)—can cause [...] Read more.

Zinc compounds in polyolefin films regulate the transmission of UV-VIS radiation, affect mechanical properties and antimicrobial activity. According to hypothesis, the use of zinc- containing masterbatches in polyethylene films (PE) with different chemical nature—hydrophilic zinc oxide (ZO) and hydrophobic zinc stearate (ZS)—can cause a synergistic effect, especially due to their antimicrobial properties. PE films obtained on an industrial scale containing zinc oxide and zinc stearate masterbatches were evaluated for antimicrobial activity against E. coli and S. aureus strains. The morphology of the samples (SEM), composition (EDX), UV barrier and transparency, mechanical properties and global migration level were also determined. SEM micrographs confirmed the good dispersion of zinc additives in the PE matrix. The use of both masterbatches in one material caused a synergistic effect of antimicrobial activity against both bacterial strains. The ZO masterbatch reduced the transparency of films, increased their UV-barrier ability and improved tensile strength, while the ZS masterbatch did not significantly change the tested parameters. The global migration limit was not exceeded for any of the samples. The use of ZO and ZS masterbatch mixtures enables the design of packaging with high microbiological protection with a controlled transmission for UV and VIS radiation. Full article

(This article belongs to the Special Issue Current Trends in Antimicrobial Polymeric Materials)

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22 pages, 785 KiB

Open AccessReview

An Insight into the Structural Diversity and Clinical Applicability of Polyurethanes in Biomedicine

by Laura-Cristina Rusu, Lavinia Cosmina Ardelean, Adriana-Andreea Jitariu, Catalin Adrian Miu and Caius Glad Streian

Polymers 2020, 12(5), 1197; https://doi.org/10.3390/polym12051197 - 24 May 2020

Cited by 61 | Viewed by 6730

Abstract

Due to their mechanical properties, ranging from flexible to hard materials, polyurethanes (PUs) have been widely used in many industrial and biomedical applications. PUs’ characteristics, along with their biocompatibility, make them successful biomaterials for short and medium-duration applications. The morphology of PUs includes [...] Read more.

Due to their mechanical properties, ranging from flexible to hard materials, polyurethanes (PUs) have been widely used in many industrial and biomedical applications. PUs’ characteristics, along with their biocompatibility, make them successful biomaterials for short and medium-duration applications. The morphology of PUs includes two structural phases: hard and soft segments. Their high mechanical resistance featuresare determined by the hard segment, while the elastomeric behaviour is established by the soft segment. The most important biomedical applications of PUs include antibacterial surfaces and catheters, blood oxygenators, dialysis devices, stents, cardiac valves, vascular prostheses, bioadhesives/surgical dressings/pressure-sensitive adhesives, drug delivery systems, tissue engineering scaffolds and electrospinning, nerve generation, pacemaker lead insulation and coatings for breast implants. The diversity of polyurethane properties, due to the ease of bulk and surface modification, plays a vital role in their applications. Full article

(This article belongs to the Special Issue Biomedical Polymer Materials II)

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13 pages, 4289 KiB

Open AccessArticle

Study on Optimization of Damping Performance and Damping Temperature Range of Silicone Rubber by Polyborosiloxane Gel

by Jiang Zhao, Nan Jiang, Dongsheng Zhang, Bobing He and Xian Chen

Polymers 2020, 12(5), 1196; https://doi.org/10.3390/polym12051196 - 24 May 2020

Cited by 36 | Viewed by 8950

Abstract

Polyborosiloxane gel (PBS-gel) with shear hardening properties was prepared by cross-linking boric acid and hydroxyl-terminated polydimethylsiloxane through B–O–Si dynamic covalent bonding. The prepared PBS gel was mixed with methyl vinyl silicone rubber (MVQ), and a benzoyl peroxide (BPO) cross-linking agent was added to [...] Read more.

Polyborosiloxane gel (PBS-gel) with shear hardening properties was prepared by cross-linking boric acid and hydroxyl-terminated polydimethylsiloxane through B–O–Si dynamic covalent bonding. The prepared PBS gel was mixed with methyl vinyl silicone rubber (MVQ), and a benzoyl peroxide (BPO) cross-linking agent was added to vulcanize the silicone rubber. At the same time, the gel molecules were co-vulcanizing with MVQ to produce molecular cross-linking. The effects of PBS-gel on the damping properties of silicone rubber were analyzed by dynamic rheological test, Fourier transform infrared spectroscopy and dynamic mechanical analysis. The results demonstrated that the damping performance of MVQ/PBS rubber is greatly improved and the rubber has a tanδ > 0.3 in the range of −25~125 °C. The shear-hardening gel is uniformly dispersed in the system, due to the combined action of covalent bonds and intermolecular forces, which act as an active molecular chain that can efficiently dissipate and transfer energy inside the silicone rubber. Full article

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47 pages, 10107 KiB

Open AccessReview

Positively Charged Polymers as Promising Devices against Multidrug Resistant Gram-Negative Bacteria: A Review

by Silvana Alfei and Anna Maria Schito

Polymers 2020, 12(5), 1195; https://doi.org/10.3390/polym12051195 - 23 May 2020

Cited by 94 | Viewed by 8562

Abstract

Antibiotic resistance has increased markedly in Gram-negative bacteria, causing severe infections intractable with traditional drugs and amplifying mortality and healthcare costs. Consequently, to find novel antimicrobial compounds, active on multidrug resistant bacteria, is mandatory. In this regard, cationic antimicrobial peptides (CAMPs)—able to kill [...] Read more.

Antibiotic resistance has increased markedly in Gram-negative bacteria, causing severe infections intractable with traditional drugs and amplifying mortality and healthcare costs. Consequently, to find novel antimicrobial compounds, active on multidrug resistant bacteria, is mandatory. In this regard, cationic antimicrobial peptides (CAMPs)—able to kill pathogens on contact—could represent an appealing solution. However, low selectivity, hemolytic toxicity and cost of manufacturing, hamper their massive clinical application. In the recent years—starting from CAMPs as template molecules—less toxic and lower-cost synthetic mimics of CAMPs, including cationic peptides, polymers and dendrimers, have been developed. Although the pending issue of hemolytic toxicity and biodegradability is still left not completely solved, cationic antimicrobial polymers (CAPs), compared to small drug molecules, thanks to their high molecular weight, own appreciable selectivity, reduced toxicity toward eukaryotic cells, more long-term activity, stability and non-volatility. With this background, an updated overview concerning the main manufactured types of CAPs, active on Gram-negative bacteria, is herein reported, including synthetic procedure and action’s mechanism. Information about their structures, antibacterial activity, advantages and drawbacks, was reported in the form of tables, which allow faster consultation and quicker learning concerning current CAPs state of the art, in order not to retrace reviews already available. Full article

(This article belongs to the Special Issue Current Trends in Antimicrobial Polymeric Materials)

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26 pages, 13892 KiB

Open AccessArticle

A New Multiparameter Model for Multiaxial Fatigue Life Prediction of Rubber Materials

by Rafael Tobajas, Daniel Elduque, Elena Ibarz, Carlos Javierre and Luis Gracia

Polymers 2020, 12(5), 1194; https://doi.org/10.3390/polym12051194 - 23 May 2020

Cited by 12 | Viewed by 4172

Abstract

Most of the mechanical components manufactured in rubber materials experience fluctuating loads, which cause material fatigue, significantly reducing their life. Different models have been used to approach this problem. However, most of them just provide life prediction only valid for each of the [...] Read more.

Most of the mechanical components manufactured in rubber materials experience fluctuating loads, which cause material fatigue, significantly reducing their life. Different models have been used to approach this problem. However, most of them just provide life prediction only valid for each of the specific studied material and type of specimen used for the experimental testing. This work focuses on the development of a new generalized model of multiaxial fatigue for rubber materials, introducing a multiparameter variable to improve fatigue life prediction by considering simultaneously relevant information concerning stresses, strains, and strain energies. The model is verified through its correlation with several published fatigue tests for different rubber materials. The proposed model has been compared with more than 20 different parameters used in the specialized literature, calculating the value of the R² coefficient by comparing the predicted values of every model, with the experimental ones. The obtained results show a significant improvement in the fatigue life prediction. The proposed model does not aim to be a universal and definitive approach for elastomer fatigue, but it provides a reliable general tool that can be used for processing data obtained from experimental tests carried out under different conditions. Full article

(This article belongs to the Special Issue Assessment of the Ageing and Durability of Polymers II: Procedures and Reliability)

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14 pages, 3277 KiB

Open AccessArticle

High-Molecular-Weight PLA-b-PEO-b-PLA Triblock Copolymer Templated Large Mesoporous Carbons for Supercapacitors and CO₂ Capture

by Mohamed Gamal Mohamed, Wei-Shih Hung, Ahmed F. M. EL-Mahdy, Mahmoud M. M. Ahmed, Lizong Dai, Tao Chen and Shiao-Wei Kuo

Polymers 2020, 12(5), 1193; https://doi.org/10.3390/polym12051193 - 23 May 2020

Cited by 22 | Viewed by 5354

Abstract

High-molecular-weight PLA₄₄₀-b-PEO₄₅₄-b-PLA₄₄₀ (LEL) triblock copolymer was synthesized through simple ring-opening polymerization (ROP) by using the commercial homopolymer HO-PEO₄₅₄-OH as the macro-initiator. The material acted as a single template to prepare the large [...] Read more.

High-molecular-weight PLA₄₄₀-b-PEO₄₅₄-b-PLA₄₄₀ (LEL) triblock copolymer was synthesized through simple ring-opening polymerization (ROP) by using the commercial homopolymer HO-PEO₄₅₄-OH as the macro-initiator. The material acted as a single template to prepare the large mesoporous carbons by using resol-type phenolic resin as a carbon source. Self-assembled structures of phenolic/LEL blends mediated by hydrogen bonding interaction were determined by FTIR and SAXS analyses. Through thermal curing and carbonization procedures, large mesoporous carbons (>50 nm) with a cylindrical structure and high surface area (>600 m²/g) were obtained because the OH units of phenolics prefer to interact with PEO block rather than PLA block, as determined by FTIR spectroscopy. Furthermore, higher CO₂ capture and good energy storage performance were observed for this large mesoporous carbon, confirming that the proposed approach provides an easy method for the preparation of large mesoporous materials. Full article

(This article belongs to the Special Issue Functional and Conductive Polymer Thin Films II)

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16 pages, 7272 KiB

Open AccessArticle

Microstructure and Mechanical Properties of Carboxylated Nitrile Butadiene Rubber/Epoxy/XNBR-grafted Halloysite Nanotubes Nanocomposites

by Seyed Mohamad Reza Paran, Ghasem Naderi, Heydar Mosallanezhad, Elnaz Movahedifar, Krzysztof Formela and Mohammad Reza Saeb

Polymers 2020, 12(5), 1192; https://doi.org/10.3390/polym12051192 - 23 May 2020

Cited by 26 | Viewed by 4878

Abstract

The effect of various amounts of carboxylated nitrile butadiene rubber (XNBR) functionalized halloysite nanotubes (XHNTs) on the cure characteristics, mechanical and swelling behavior of XNBR/epoxy compounds was experimentally and theoretically investigated. The morphology of the prepared XNBR/epoxy/XHNTs nanocomposites was imaged using scanning electron [...] Read more.

The effect of various amounts of carboxylated nitrile butadiene rubber (XNBR) functionalized halloysite nanotubes (XHNTs) on the cure characteristics, mechanical and swelling behavior of XNBR/epoxy compounds was experimentally and theoretically investigated. The morphology of the prepared XNBR/epoxy/XHNTs nanocomposites was imaged using scanning electron microscopy (SEM). The effects of various XNBR-grafted nanotubes on the damping factor of nanocomposites were evaluated by dynamic mechanical thermal analysis (DMTA). The cure behavior characterization indicated a fall in the scorch time, but a rise in the cure rate with higher loading of XHNTs into the XNBR/epoxy nanocomposites. SEM micrographs of tensile fracture surfaces were indicative of a rougher fracture surface with a uniform dispersion state of nanotubes into the polymer matrix in the XNBR/epoxy/XHNTs nanocomposites. The stress–strain behavior studies of XNBR/epoxy/XHNTs nanocomposites showed a higher tensile strength up to 40% with 7 wt % XHNTs loading. The theoretical predictions of uniaxial tensile behavior of nanocomposites using Bergström–Boyce model revealed that some of the material parameters were considerably changed with the XHNTs loading. Furthermore, the used theoretical model precisely predicted the nonlinear large strain hyperelastic behavior of nanocomposites. Full article

(This article belongs to the Special Issue Advances in Rubber Composites)

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18 pages, 4852 KiB

Open AccessFeature PaperArticle

Development and Performance of Bioactive Compounds-Loaded Cellulose/Collagen/Polyurethane Materials

by Iuliana Spiridon, Narcis Anghel, Maria Valentina Dinu, Stelian Vlad, Adrian Bele, Bianca Iulia Ciubotaru, Liliana Verestiuc and Daniela Pamfil

Polymers 2020, 12(5), 1191; https://doi.org/10.3390/polym12051191 - 23 May 2020

Cited by 33 | Viewed by 3685

Abstract

Here we present a new biomaterial based on cellulose, collagen and polyurethane, obtained by dissolving in butyl imidazole chloride. This material served as a matrix for the incorporation of tannin and lipoic acid, as well as bioactive substances with antioxidant properties. The introduction [...] Read more.

Here we present a new biomaterial based on cellulose, collagen and polyurethane, obtained by dissolving in butyl imidazole chloride. This material served as a matrix for the incorporation of tannin and lipoic acid, as well as bioactive substances with antioxidant properties. The introduction of these bioactive principles into the base matrix led to an increase of the compressive strength in the range 105–139 kPa. An increase of 29.85% of the mucoadhesiveness of the film containing tannin, as compared to the reference, prolongs the bioavailability of the active substance; a fact also demonstrated by the controlled release studies. The presence of bioactive principles, as well as tannins and lipoic acid, gives biomaterials an antioxidant capacity on average 40%–50% higher compared to the base matrix. The results of the tests of the mechanical resistance, mucoadhesiveness, bioadhesiveness, water absorption and antioxidant capacity of active principles recommend these biomaterials for the manufacture of cosmetic masks or patches. Full article

(This article belongs to the Special Issue Functional Chitosan-Based Composites)

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13 pages, 8639 KiB

Open AccessArticle

Transparent Ultraviolet (UV)-Shielding Films Made from Waste Hemp Hurd and Polyvinyl Alcohol (PVA)

by Yi Zhang, Rechana Remadevi, Juan P. Hinestroza, Xungai Wang and Maryam Naebe

Polymers 2020, 12(5), 1190; https://doi.org/10.3390/polym12051190 - 22 May 2020

Cited by 52 | Viewed by 6146

Abstract

This work proposes a new approach to fabricate highly transparent and flexible composite films that exhibit enhanced UV-shielding properties. Lignin has innate UV-shielding properties. However, when purified lignin, which is conventionally extracted through chemical treatment, is mixed with polymeric materials, its presence negatively [...] Read more.

This work proposes a new approach to fabricate highly transparent and flexible composite films that exhibit enhanced UV-shielding properties. Lignin has innate UV-shielding properties. However, when purified lignin, which is conventionally extracted through chemical treatment, is mixed with polymeric materials, its presence negatively influences the transparency of the resulting composite. High transparency and UV-shielding are desirable properties for many applications. In this study, composites were made by mixing lignocellulose particles and polyvinyl alcohol (PVA), where lignocellulose particles were obtained from ball-milled waste hemp hurd without chemical treatments. The UV-shielding properties of the resulting composite film, as a function of hemp/PVA weight ratios, were investigated. The intermolecular interactions between the hemp particles and the PVA were characterized using infrared spectroscopy with the presence of –C=O group at 1655 cm⁻¹, providing evidence that the chemical structure of lignin was preserved. The fabricated hemp/PVA films exhibit stronger UV-shielding, in the UVA-I range (340–400 nm) than TiO₂/PVA films. The composite films also showed comparable water vapor permeability (WVP) with commercial packaging plastic film made of HDPE (high-density polyethylene). The optimization experiments were reported, with aim at understanding the balance between the UV-shielding and mechanical properties of the hemp/PVA films. The findings of this work can be applicable to the packaging, food and cosmetic industries where UV shielding is of utmost importance, hence adding value to hemp hurd waste. Full article

(This article belongs to the Special Issue Biodegradable and Sustainable Polymers)

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1 pages, 166 KiB

Open AccessErratum

Erratum: Surface Energy of Filtration Media Influencing the Filtration Performance against Solid Particles, Oily Aerosol, and Bacterial Aerosol. Polymers 2019, 11, 935

by Seojin Jung, Jaejin An, Hyungjin Na and Jooyoun Kim

Polymers 2020, 12(5), 1189; https://doi.org/10.3390/polym12051189 - 22 May 2020

Cited by 2 | Viewed by 1750

Abstract

The authors wish to make a change to the published paper [...] Full article

(This article belongs to the Special Issue Polymer-Based Materials as Ecological Adsorbents for Environmental Protection)

11 pages, 3254 KiB

Open AccessArticle

Effects of Solvent Vapor Annealing on Morphology and Charge Transport of Poly(3-hexylthiophene) (P3HT) Films Incorporated with Preformed P3HT Nanowires

by Mingu Jang, Yang-Il Huh and Mincheol Chang

Polymers 2020, 12(5), 1188; https://doi.org/10.3390/polym12051188 - 22 May 2020

Cited by 11 | Viewed by 4819

Abstract

We systematically studied the influence of solvent vapor annealing on the molecular ordering, morphologies, and charge transport properties of poly(3-hexylthiophene) (P3HT) thin films embedded with preformed crystalline P3HT nanowires (NWs). Solvent vapor annealing (SVA) with chloroform (CF) was found to profoundly impact on [...] Read more.

We systematically studied the influence of solvent vapor annealing on the molecular ordering, morphologies, and charge transport properties of poly(3-hexylthiophene) (P3HT) thin films embedded with preformed crystalline P3HT nanowires (NWs). Solvent vapor annealing (SVA) with chloroform (CF) was found to profoundly impact on the structural and morphological changes, and thus on the charge transport characteristics, of the P3HT-NW-embedded P3HT films. With increased annealing time, the density of crystalline P3HT NWs was increased within the resultant films, and also intra- and intermolecular interactions of the corresponding films were significantly improved. As a result, the P3HT-NW-embedded P3HT films annealed with CF vapor for 20 min resulted in a maximized charge carrier mobility of ~0.102 cm² V⁻¹ s⁻¹, which is higher than that of pristine P3HT films by 4.4-fold (μ = ~0.023 cm² V⁻¹ s⁻¹). Full article

(This article belongs to the Special Issue Polymeric Materials for Electrical Applications)

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13 pages, 4976 KiB

Open AccessEditor’s ChoiceArticle

Development of Poly(l-Lactic Acid)-Based Bending Actuators

by Daniela M. Correia, Liliana C. Fernandes, Bárbara D.D. Cruz, Gabriela Botelho, Verónica de Zea Bermudez and Senentxu Lanceros-Méndez

Polymers 2020, 12(5), 1187; https://doi.org/10.3390/polym12051187 - 22 May 2020

Cited by 10 | Viewed by 3865

Abstract

This work reports on the development of bending actuators based on poly(l-lactic acid) (PLLA)/ionic liquid (IL) blends, through the incorporation of 40% wt. of the 1-ethyl-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][TFSI]) IL. The films, obtained by solvent casting at room temperature and 50 °C, [...] Read more.

This work reports on the development of bending actuators based on poly(l-lactic acid) (PLLA)/ionic liquid (IL) blends, through the incorporation of 40% wt. of the 1-ethyl-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][TFSI]) IL. The films, obtained by solvent casting at room temperature and 50 °C, were subjected to several post-thermal treatments at 70, 90, 120 and 140 °C, in order to modify the crystallinity of the films. The influence of the drying temperature and of [Emim][TFSI] blending on the morphological, structural, mechanical and electrical properties of the composite materials were studied. The IL induced the formation of a porous surface independently of the processing conditions. Moreover, the [Emim][TFSI] dopant and the post-thermal treatments at 70 °C promoted an increase of the degree of crystallinity of the samples. No significant changes were observed in the degree of crystallinity and Young Modulus for samples with thermal treatment between 70 and 140 °C. The viability of the developed high ionic conductive blends for applications as soft actuators was evaluated. A maximum displacement of 1.7 mm was achieved with the PLLA/[Emim][TFSI] composite prepared at 50 °C and thermally treated at 140 °C, for an applied voltage of 10 Vpp, at a frequency of 100 mHz. This work highlights interesting avenues for the use of PLLA in the field of actuators. Full article

(This article belongs to the Special Issue Conducting Polymers for Advanced Applications)

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11 pages, 3581 KiB

Open AccessArticle

A Facile Fabrication of Biodegradable and Biocompatible Cross-Linked Gelatin as Screen Printing Substrates

by Pei-Leun Kang, Yu-Hsin Lin, Kalpana Settu, Ching-Shu Yen, Chin-Yi Yeh, Jen-Tsai Liu, Ching-Jung Chen and Shwu-Jen Chang

Polymers 2020, 12(5), 1186; https://doi.org/10.3390/polym12051186 - 22 May 2020

Cited by 7 | Viewed by 3483

Abstract

This study focuses on preparation and valuation of the biodegradable, native, and modified gelatin film as screen-printing substrates. Modified gelatin film was prepared by crosslinking with various crosslinking agents and the electrode array was designed by screen-printing. It was observed that the swelling [...] Read more.

This study focuses on preparation and valuation of the biodegradable, native, and modified gelatin film as screen-printing substrates. Modified gelatin film was prepared by crosslinking with various crosslinking agents and the electrode array was designed by screen-printing. It was observed that the swelling ratio of C-2, crosslinked with glutaraldehyde and EDC/NHS (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide) was found to be lower (3.98%) than that of C-1 (crosslinked with only glutaraldehyde) (8.77%) and C-0 (without crosslinking) (28.15%). The obtained results indicate that the swelling ratios of both C-1 and C-2 were found to be lower than that of C-0 (control one without crosslinking). The Young’s modulus for C-1 and C-2 was found to be 8.55 ± 0.57 and 23.72 ± 2.04 kPa, respectively. Hence, it was conveyed that the mechanical strength of C-2 was found to be two times higher than that of C-l, suggesting that the mechanical strength was enhanced upon dual crosslinking in this study also. The adhesion study indicates that silver ink adhesion on the gelation surface is better than that of carbon ink. In addition, the electrical response of C-2 with a screen-printed electrode (SPE) was found to be the same as the commercial polycarbonate (PC) substrate. The result of MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay suggested that the silver SPE on C-2 was non-cytotoxic toward L929 fibroblast cells proliferation. The results indicated that C-2 gelatin is a promising material to act as a screen-printing substrate with excellent biodegradable and biocompatible properties. Full article

(This article belongs to the Special Issue Sustainable Bio-Based Polymers: Towards a Circular Bioeconomy)

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15 pages, 1317 KiB

Open AccessArticle

Hydrophobically Functionalized Poly(Acrylic Acid) Comprising the Ester-Type Labile Spacer: Synthesis and Self-Organization in Water

by Łukasz Lamch, Sylwia Ronka, Izabela Moszyńska, Piotr Warszyński and Kazimiera A. Wilk

Polymers 2020, 12(5), 1185; https://doi.org/10.3390/polym12051185 - 22 May 2020

Cited by 17 | Viewed by 5014

Abstract

One of the most important properties of hydrophobically functionalized polyelectrolytes (HF-PEs) and their assemblies is their ability to encapsulate hydrophobic/amphiphilic agents and provide release on demand of the entrapped payload. The aim of the present work was to synthesize and study self-organization behavior [...] Read more.

One of the most important properties of hydrophobically functionalized polyelectrolytes (HF-PEs) and their assemblies is their ability to encapsulate hydrophobic/amphiphilic agents and provide release on demand of the entrapped payload. The aim of the present work was to synthesize and study self-organization behavior in aqueous solution of hydrophobically functionalized poly(acrylic acid) (PAA) comprising the ester-type pH labile moiety with various degrees of hydrophobization and side-chain lengths in the absence and presence of appropriate mono- and polyvalent electrolytes (i.e., NaCl or CaCl₂). The synthesis and purification of hydrophobically functionalized PAA were performed under mild conditions in order to avoid chemical degradation of the polymers. The modified polyelectrolytes self-assembly in aqueous systems was monitored using diffusion-ordered nuclear magnetic resonance (DOSY NMR). The performed studies, supported by the all-atoms molecular dynamics simulations, revealed a strong dependence of polyelectrolyte self-assembled state on concentration—specific concentration regions with the coexistence of both smaller and larger aggregates were observed (values of hydrodynamic diameter D_H around one nanometer and between two to six nanometers, respectively). Our investigations enabled us to gain crucial information about the self-assembly of the hydrophobically functionalized poly(acrylic acid) and opened the possibility of understanding and predicting its performance under various conditions. Full article

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21 pages, 5033 KiB

Open AccessReview

Polymer-Based MEMS Electromagnetic Actuator for Biomedical Application: A Review

by Jumril Yunas, Budi Mulyanti, Ida Hamidah, Muzalifah Mohd Said, Roer Eka Pawinanto, Wan Amar Fikri Wan Ali, Ayub Subandi, Azrul Azlan Hamzah, Rhonira Latif and Burhanuddin Yeop Majlis

Polymers 2020, 12(5), 1184; https://doi.org/10.3390/polym12051184 - 22 May 2020

Cited by 84 | Viewed by 11511

Abstract

In this study, we present a comprehensive review of polymer-based microelectromechanical systems (MEMS) electromagnetic (EM) actuators and their implementation in the biomedical engineering field. The purpose of this review is to provide a comprehensive summary on the latest development of electromagnetically driven microactuators [...] Read more.

In this study, we present a comprehensive review of polymer-based microelectromechanical systems (MEMS) electromagnetic (EM) actuators and their implementation in the biomedical engineering field. The purpose of this review is to provide a comprehensive summary on the latest development of electromagnetically driven microactuators for biomedical application that is focused on the movable structure development made of polymers. The discussion does not only focus on the polymeric material part itself, but also covers the basic mechanism of the mechanical actuation, the state of the art of the membrane development and its application. In this review, a clear description about the scheme used to drive the micro-actuators, the concept of mechanical deformation of the movable magnetic membrane and its interaction with actuator system are described in detail. Some comparisons are made to scrutinize the advantages and disadvantages of electromagnetic MEMS actuator performance. The previous studies and explanations on the technology used to fabricate the polymer-based membrane component of the electromagnetically driven microactuators system are presented. The study on the materials and the synthesis method implemented during the fabrication process for the development of the actuators are also briefly described in this review. Furthermore, potential applications of polymer-based MEMS EM actuators in the biomedical field are also described. It is concluded that much progress has been made in the material development of the actuator. The technology trend has moved from the use of bulk magnetic material to using magnetic polymer composites. The future benefits of these compact flexible material employments will offer a wide range of potential implementation of polymer composites in wearable and portable biomedical device applications. Full article

(This article belongs to the Special Issue Functional Polymers in Sensors and Actuators: Fabrication and Analysis)

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13 pages, 3754 KiB

Open AccessArticle

Synthesis of Polylactic Acid Initiated through Biobased Antioxidants: Towards Intrinsically Active Food Packaging

by Marco Aldo Ortenzi, Stefano Gazzotti, Begonya Marcos, Stefano Antenucci, Stefano Camazzola, Luciano Piergiovanni, Hermes Farina, Giuseppe Di Silvestro and Luisella Verotta

Polymers 2020, 12(5), 1183; https://doi.org/10.3390/polym12051183 - 21 May 2020

Cited by 17 | Viewed by 3918

Abstract

Polylactide (PLA)-based polymers, functionalized with biobased antioxidants, were synthesized, to develop an intrinsically active, biobased and potentially biodegradable material for food packaging applications. To achieve this result, phenolic antioxidants were exploited as initiators in the ring opening polymerization of l-lactide. The molecular [...] Read more.

Polylactide (PLA)-based polymers, functionalized with biobased antioxidants, were synthesized, to develop an intrinsically active, biobased and potentially biodegradable material for food packaging applications. To achieve this result, phenolic antioxidants were exploited as initiators in the ring opening polymerization of l-lactide. The molecular weight, thermal properties and in vitro radical scavenging activity of the polymers obtained were compared with the ones of a PLA Natureworks 4043D, commonly used for flexible food packaging applications. The most promising synthesized polymer, bearing vanillyl alcohol as initiator (PLA-VA), was evaluated for active food packaging applications. Packaging with PLA-VA films reduced color and fat oxidation of salami during its shelf life. Full article

(This article belongs to the Special Issue Biodegradable and Biobased Polymers Obtained via Step Polymerization)

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20 pages, 5939 KiB

Open AccessArticle

Synthesis, Characterization and Sorption Capacity Examination for a Novel Hydrogel Composite Based on Gellan Gum and Graphene Oxide (GG/GO)

by Cristina Modrogan, Andreea Mădălina Pandele, Constantin Bobirică, Dan Dobrotǎ, Annette Madelene Dăncilă, Gabriel Gârleanu, Oanamari Daniela Orbuleţ, Claudia Borda, Delia Gârleanu and Cristina Orbeci

Polymers 2020, 12(5), 1182; https://doi.org/10.3390/polym12051182 - 21 May 2020

Cited by 22 | Viewed by 4345

Abstract

A novel hydrogel composite based on gellan gum and graphene oxide (GG/GO) was synthesized, characterized and tested for sorption capacity in this work. The microstructural, thermogravimetric and spectroscopic analysis confirmed the formation of the GG/GO composite. Comparative batch sorption experiments revealed a sorption [...] Read more.

A novel hydrogel composite based on gellan gum and graphene oxide (GG/GO) was synthesized, characterized and tested for sorption capacity in this work. The microstructural, thermogravimetric and spectroscopic analysis confirmed the formation of the GG/GO composite. Comparative batch sorption experiments revealed a sorption capacity of the GG/GO composite for Zn (II) ions of approximately 2.3 higher than that of pure GG. The GG/GO composite exhibits a maximum sorption capacity of 272.57 mg/g at a pH of Zn (II) initial solution of 6. Generally, the sorption capacity of the sorbents is approximately 1.5 higher in slightly acidic conditions (pH 6) comparative with that for strong acidic conditions (pH 3). The sorption isotherms revealed that the sorption followed a monolayer/homogenous behavior. The sorption kinetic data were well fitted by the pseudo-second-order kinetic model, and were consistent with those derived from sorption isotherms. The intraparticle diffusion was considered to be the rate-determining step. Two main sorption mechanisms for Zn (II) were identified namely, ion exchange at low pH values, and both ion exchange and chemisorption in weekly acidic conditions. Full article

(This article belongs to the Special Issue Biopolymer-Based Composites: Current State of Knowledge and Future Perspectives)

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17 pages, 3625 KiB

Open AccessArticle

Construction of NIR Light Controlled Micelles with Photothermal Conversion Property: Poly(poly(ethylene glycol)methyl ether methacrylate) (PPEGMA) as Hydrophilic Block and Ketocyanine Dye as NIR Photothermal Conversion Agent

by Lan Yao, Haihui Li, Kai Tu, Lifen Zhang, Zhenping Cheng and Xiulin Zhu

Polymers 2020, 12(5), 1181; https://doi.org/10.3390/polym12051181 - 21 May 2020

Cited by 5 | Viewed by 3369

Abstract

Polymeric nanomaterials made from amphiphilic block copolymers are increasingly used in the treatment of tumor tissues. In this work, we firstly synthesized the amphiphilic block copolymer PBnMA-b-P(BAPMA-co-PEGMA) via reversible addition-fragmentation chain transfer (RAFT) polymerization using benzyl methacrylate (BnMA), poly [...] Read more.

Polymeric nanomaterials made from amphiphilic block copolymers are increasingly used in the treatment of tumor tissues. In this work, we firstly synthesized the amphiphilic block copolymer PBnMA-b-P(BAPMA-co-PEGMA) via reversible addition-fragmentation chain transfer (RAFT) polymerization using benzyl methacrylate (BnMA), poly (ethylene glycol) methyl ether methacrylate (PEGMA), and 3-((tert-butoxycarbonyl)amino)propyl methacrylate (BAPMA) as the monomers. Subsequently, PBnMA-b-P(APMA-co-PEGMA)@NIR 800 with photothermal conversion property was obtained by deprotection of the tert-butoxycarbonyl (BOC) groups of PBAPMA chains with trifluoroacetic acid (TFA) and post-modification with carboxyl functionalized ketocyanine dye (NIR 800), and it could self-assemble into micelles in CH₃OH/water mixed solvent. The NIR photothermal conversion property of the post-modified micelles were investigated. Under irradiation with NIR light (λ_max = 810 nm, 0.028 W/cm²) for 1 h, the temperature of the modified micelles aqueous solution increased to 53 °C from 20 °C, which showed the excellent NIR photothermal conversion property. Full article

(This article belongs to the Section Polymer Chemistry)

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15 pages, 5004 KiB

Open AccessArticle

Biopolymer-Based Hybrids as Effective Admixtures for Cement Composites

by Agnieszka Ślosarczyk, Izabela Klapiszewska, Patryk Jędrzejczak, Łukasz Klapiszewski and Teofil Jesionowski

Polymers 2020, 12(5), 1180; https://doi.org/10.3390/polym12051180 - 21 May 2020

Cited by 12 | Viewed by 4386

Abstract

In the framework of this publication, silica-lignin hybrid materials were designed, obtained, characterized and then used as admixtures for cement composites. High-energy mechanical grinding of individual components was used to produce the systems that allowed ensuring adequate homogeneity of the final products. As [...] Read more.

In the framework of this publication, silica-lignin hybrid materials were designed, obtained, characterized and then used as admixtures for cement composites. High-energy mechanical grinding of individual components was used to produce the systems that allowed ensuring adequate homogeneity of the final products. As a result of the analysis of Fourier transform infrared spectroscopy, it has been confirmed that weak physical interactions occur between the components. This allowed classifying the resulting systems as I class hybrid materials. In addition, the efficiency of obtaining final products was also inferred on the basis of obtained porous structure parameters and colorimetric data. The achieved bio-admixture with different weight ratios of silica and lignin was added to cement pastes in the amount ranging from 0.5 to 1 wt.%. The study showed that increasing the ratio of lignin in the admixture from 0.15 to 1 wt.% had a positive effect on the rheological properties of the pastes, while the mechanical properties of the composite were deteriorated. In turn, a higher amount of silica in the admixture acted in reverse. The most favorable results were obtained for a silica-lignin bio-admixture with a weight ratio of components equal to 5:1 wt./wt. A significant increase in compressive strength was gained at satisfactory plasticity of the paste. Full article

(This article belongs to the Special Issue Biopolymer-Based Composites: Current State of Knowledge and Future Perspectives)

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15 pages, 5118 KiB

Open AccessArticle

Effect of Different Phosphate Glass Compositions on the Process-Induced Macromolecular Dynamics of Polyamide 66

by Imane Belyamani and Mohammad K. Hassan

Polymers 2020, 12(5), 1179; https://doi.org/10.3390/polym12051179 - 21 May 2020

Cited by 3 | Viewed by 3260

Abstract

The present study provides a fundamental understanding of the mechanism of action of special new phosphate glass (P-glass) systems, having different glass transition temperatures (T_g), in polyamide 66 (PA66). Dynamic mechanical analysis (DMA) revealed that the T_g of PA66/low [...] Read more.

The present study provides a fundamental understanding of the mechanism of action of special new phosphate glass (P-glass) systems, having different glass transition temperatures (T_g), in polyamide 66 (PA66). Dynamic mechanical analysis (DMA) revealed that the T_g of PA66/low T_g P-glass (ILT-1) was significantly shifted to a lower T_g (65 °C), and another transition appeared at high temperature (166 °C). This was supported by a drop in the melting point and the crystallinity of the PA66/ILT-1 hybrid material as detected by differential scanning calorimetry (DSC). The dielectric spectroscopic investigation on the networks’ molecular level structural variations (T_g and sub-T_g relaxations) agreed very well with the DMA and DSC findings. Contrary to intermediate T_g(IIT-3) and high T_g P-glass (IHT-1) based materials, the PA66/ILT-1 hybrid material showed an evidence of splitting the PA66 T_g relaxations into two peaks, thus confirming a strong interaction between PA66 and ILT-1 (low T_g P-glass). Nevertheless, the three different P-glass compositions did not show any effect on the PA66 sub-T_g relaxations (related to the –NH₂ and –OH chain end groups’ motion). Full article

(This article belongs to the Special Issue Polymer Nanocomposites: Processing, Degradation and Applications)

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10 pages, 2231 KiB

Open AccessArticle

Delayed Addition of Template Molecules Enhances the Binding Properties of Diclofenac-Imprinted Polymers

by Laura Anfossi, Simone Cavalera, Fabio Di Nardo, Giulia Spano, Cristina Giovannoli and Claudio Baggiani

Polymers 2020, 12(5), 1178; https://doi.org/10.3390/polym12051178 - 21 May 2020

Cited by 7 | Viewed by 3659

Abstract

It has been reported that in the molecular imprinting technique, the use of preformed oligomers instead of functional monomers increases the stability of the non-covalent interactions with the template molecule, providing a sharp gain in terms of binding properties for the resulting imprinted [...] Read more.

It has been reported that in the molecular imprinting technique, the use of preformed oligomers instead of functional monomers increases the stability of the non-covalent interactions with the template molecule, providing a sharp gain in terms of binding properties for the resulting imprinted polymer. Based on this theory, we assumed that the delayed addition of template molecules to a polymerization mixture enhances the binding properties of the resulting polymer. To verify this hypothesis, we imprinted several mixtures of 4-vinylpyridine/ethylene dimethacrylate (1:6 mol/mol) in acetonitrile by adding diclofenac progressively later from the beginning of the polymerization process. After polymerization, the binding isotherms of imprinted and non-imprinted materials were measured in acetonitrile by partition equilibrium experiments. Binding data confirm our hypothesis, as imprinted polymers prepared by delayed addition, with delay times of 5 and 10 min, showed higher binding affinity (K_eq = 1.37 × 10⁴ L mol⁻¹ and 1.80 × 10⁴ L mol⁻¹) than the polymer obtained in the presence of template at the beginning (K_eq = 5.30 × 10³ L mol⁻¹). Similarly, an increase in the imprinting factor measured vs. the non-imprinted polymer in the binding selectivity with respect to mefenamic acid was observed. We believe that the delayed addition approach could be useful in prepar imprinted polymers with higher binding affinity and increased binding selectivity in cases of difficult imprinting polymerization. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Italy (2019,2020))

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24 pages, 3183 KiB

Open AccessEditor’s ChoiceReview

Chitosan-Based Drug Delivery System: Applications in Fish Biotechnology

by Yuanbing Wu, Ania Rashidpour, María Pilar Almajano and Isidoro Metón

Polymers 2020, 12(5), 1177; https://doi.org/10.3390/polym12051177 - 21 May 2020

Cited by 77 | Viewed by 8612

Abstract

Chitosan is increasingly used for safe nucleic acid delivery in gene therapy studies, due to well-known properties such as bioadhesion, low toxicity, biodegradability and biocompatibility. Furthermore, chitosan derivatization can be easily performed to improve the solubility and stability of chitosan–nucleic acid polyplexes, and [...] Read more.

Chitosan is increasingly used for safe nucleic acid delivery in gene therapy studies, due to well-known properties such as bioadhesion, low toxicity, biodegradability and biocompatibility. Furthermore, chitosan derivatization can be easily performed to improve the solubility and stability of chitosan–nucleic acid polyplexes, and enhance efficient target cell drug delivery, cell uptake, intracellular endosomal escape, unpacking and nuclear import of expression plasmids. As in other fields, chitosan is a promising drug delivery vector with great potential for the fish farming industry. This review highlights state-of-the-art assays using chitosan-based methodologies for delivering nucleic acids into cells, and focuses attention on recent advances in chitosan-mediated gene delivery for fish biotechnology applications. The efficiency of chitosan for gene therapy studies in fish biotechnology is discussed in fields such as fish vaccination against bacterial and viral infection, control of gonadal development and gene overexpression and silencing for overcoming metabolic limitations, such as dependence on protein-rich diets and the low glucose tolerance of farmed fish. Finally, challenges and perspectives on the future developments of chitosan-based gene delivery in fish are also discussed. Full article

(This article belongs to the Special Issue Functional Chitosan-Based Composites)

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