Macromol

18 pages, 3613 KiB

Open AccessReview

Current Research on Polyelectrolyte Nanostructures: From Molecular Interactions to Biomedical Applications

by Aristeidis Papagiannopoulos

Macromol 2021, 1(2), 155-172; https://doi.org/10.3390/macromol1020012 - 24 May 2021

Cited by 18 | Viewed by 5734

Polyelectrolytes have been at the center of interdisciplinary research for many decades. In the field of polymer science and soft matter, they have provided the dimensions of electrostatic interactions, which opens a vast variety of opportunities for new physical properties and applications. In [...] Read more.

Polyelectrolytes have been at the center of interdisciplinary research for many decades. In the field of polymer science and soft matter, they have provided the dimensions of electrostatic interactions, which opens a vast variety of opportunities for new physical properties and applications. In biological matter, polyelectrolytes are present in many forms, from extracellular polysaccharides to complex DNA molecules and proteins. This review discusses the recent research on polyelectrolytes covering the fundamental level of their conformations and nanostructures, their molecular interactions with materials that have close relevance to bioapplications and their applications in the biomedical field. This approach is motivated by the fact that the polyelectrolyte research is constantly active in all the aforementioned levels and continually affects many critical scientific areas. Full article

(This article belongs to the Special Issue Polymers in Nanocarrier Systems)

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25 pages, 6054 KiB

Open AccessReview

Chitosan Adsorbent Derivatives for Pharmaceuticals Removal from Effluents: A Review

by Efstathios V. Liakos, Maria Lazaridou, Georgia Michailidou, Ioanna Koumentakou, Dimitra A. Lambropoulou, Dimitrios N. Bikiaris and George Z. Kyzas

Macromol 2021, 1(2), 130-154; https://doi.org/10.3390/macromol1020011 - 11 May 2021

Cited by 34 | Viewed by 5968

Abstract

Chitin is mentioned as the second most abundant and important natural biopolymer in worldwide scale. The main sources for the extraction and exploitation of this natural polysaccharide polymer are crabs and shrimps. Chitosan (poly-β-(1 → 4)-2-amino-2-deoxy-d-glucose) is the most important derivative of chitin and can [...] Read more.

Chitin is mentioned as the second most abundant and important natural biopolymer in worldwide scale. The main sources for the extraction and exploitation of this natural polysaccharide polymer are crabs and shrimps. Chitosan (poly-β-(1 → 4)-2-amino-2-deoxy-d-glucose) is the most important derivative of chitin and can be used in a wide variety of applications including cosmetics, pharmaceutical and biomedical applications, food, etc., giving this substance high value-added applications. Moreover, chitosan has applications in adsorption because it contains amino and hydroxyl groups in its molecules, and can thus contribute to many possible adsorption interactions between chitosan and pollutants (pharmaceuticals/drugs, metals, phenols, pesticides, etc.). However, it must be noted that one of the most important techniques of decontamination is considered to be adsorption because it is simple, low-cost, and fast. This review emphasizes on recently published research papers (2013–2021) and briefly describes the chemical modifications of chitosan (grafting, cross-linking, etc.), for the adsorption of a variety of emerging contaminants from aqueous solutions, and characterization results. Finally, tables are depicted from selected chitosan synthetic routes and the pH effects are discussed, along with the best-fitting isotherm and kinetic models. Full article

(This article belongs to the Collection Advances in Biodegradable Polymers)

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9 pages, 1743 KiB

Open AccessArticle

Iminopyridine Ni(II) Catalysts Affording Oily Hyperbranched Ethylene Oligomers and/or Crystalline Polyethylenes Depending on the Reaction Conditions: Possible Role of In Situ Catalyst Structure Modifications

by Ilaria D’Auria, Zeinab Saki and Claudio Pellecchia

Macromol 2021, 1(2), 121-129; https://doi.org/10.3390/macromol1020010 - 7 May 2021

Cited by 5 | Viewed by 3041

Abstract

Nickel-based ethylene polymerization catalysts have unique features, being able to produce macromolecules with a variable content of branches, resulting in polymers ranging from semicrystalline plastics to elastomers to hyperbranched amorphous waxes and oils. In addition to Brookhart’s α-diimine catalysts, iminopyridine Ni(II) complexes are [...] Read more.

Nickel-based ethylene polymerization catalysts have unique features, being able to produce macromolecules with a variable content of branches, resulting in polymers ranging from semicrystalline plastics to elastomers to hyperbranched amorphous waxes and oils. In addition to Brookhart’s α-diimine catalysts, iminopyridine Ni(II) complexes are among the most investigated systems. We report that Ni(II) complexes bearing aryliminopyridine ligands with bulky substituents both at the imino moiety and in the 6-position of pyridine afford either hyperbranched low molecular weight polyethylene oils or prevailingly linear crystalline polyethylenes or both, depending on the ligand structure and the reaction conditions. The formation of multiple active species in situ is suggested by analysis of the post-polymerization catalyst residues, showing the partial reduction of the imino function. Some related arylaminopyridine Ni(II) complexes were also synthesized and tested, showing a peculiar behavior, i.e., the number of branches of the produced polyethylenes increases while ethylene pressure increases. Full article

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9 pages, 6802 KiB

Open AccessArticle

Effect of Cyanuric Acid as an Efficient Nucleating Agent on the Crystallization of Novel Biodegradable Branched Poly(Ethylene Succinate)

by Kangjing Zhang and Zhaobin Qiu

Macromol 2021, 1(2), 112-120; https://doi.org/10.3390/macromol1020009 - 7 Apr 2021

Cited by 3 | Viewed by 2965

Abstract

Novel biodegradable branched poly(ethylene succinate) (b-PES) composites, i.e., nucleated b-PES samples, were prepared by incorporating low loadings of cyanuric acid (CA) through a solution and casting method to enhance the crystallization rate. As an efficient nucleating agent, CA could remarkably increase the nonisothermal [...] Read more.

Novel biodegradable branched poly(ethylene succinate) (b-PES) composites, i.e., nucleated b-PES samples, were prepared by incorporating low loadings of cyanuric acid (CA) through a solution and casting method to enhance the crystallization rate. As an efficient nucleating agent, CA could remarkably increase the nonisothermal melt crystallization peak temperature, shorten the crystallization half-time, accelerate the overall isothermal melt crystallization, and enhance the nucleation density of b-PES spherulites in the composites. Despite the addition of CA, the crystallization mechanism and crystal structure of b-PES remained unchanged. A possible epitaxial crystallization mechanism may account for the nucleation of b-PES crystals induced by CA. Full article

(This article belongs to the Collection Advances in Biodegradable Polymers)

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18 pages, 1513 KiB

Open AccessArticle

Effect of the Croton rhamnifolioides Essential Oil and the Inclusion Complex (OEFC/β-CD) in Antinociceptive Animal Models

by Anita Oliveira Brito Pereira Bezerra Martins, Maria Rayane Correia de Oliveira, Isabel Sousa Alcântara, Lindaiane Bezerra Rodrigues, Francisco Rafael Alves Santana Cesário, Maria Sanadia Alexandre da Silva, Fyama Ferreira e Castro, Emmily Petícia do Nascimento, Thaís Rodrigues de Albuquerque, Lucindo José Quintans Júnior, Adriano Antunes de Souza Araújo, Henrique Douglas Melo Coutinho, Irwin Rose Alencar de Menezes and Almir Gonçalves Wanderley

Macromol 2021, 1(2), 94-111; https://doi.org/10.3390/macromol1020008 - 6 Apr 2021

Cited by 3 | Viewed by 3193

Abstract

This study aims to evaluate the antinociceptive effect of the C. rhamnifolioides leaf essential oil (OEFC) and the β-cyclodextrin inclusion complex (COEFC) and investigate the pain signaling pathways involved in the antinociceptive response. The effects of the OEFC and COEFC on the central [...] Read more.

This study aims to evaluate the antinociceptive effect of the C. rhamnifolioides leaf essential oil (OEFC) and the β-cyclodextrin inclusion complex (COEFC) and investigate the pain signaling pathways involved in the antinociceptive response. The effects of the OEFC and COEFC on the central nervous system (CNS) were determined by open field and rota-rod assays, and the antinociceptive effect was evaluated via the acetic acid-induced abdominal contortions, formalin, and hot plate models. Swiss (Mus musculus) male mice (20–30 g) were used in both trials. The OEFC (200 mg/kg/v.o-orally) and COEFC (83.5 mg/kg/v.o.) did not present alterations in the CNS. The OEFC (25, 50, 100, and 200 mg/kg/vo.) and COEFC (8.35, 41.75, and 83.5 mg/kg/v.o.) demonstrated antinociceptive effects in the abdominal contortions, formalin, and hot plate tests. The OEFC (25 mg/kg/v.o.) and COEFC (8.35 mg/kg/v.o.) doses showed that the antinociceptive effect involves the activation of the opioid, cholinergic, and vanilloid systems, as well as the L-arginine/NO and α-2 adrenergic receptor pathways. The antinociceptive potential the OEFC and COEFC demonstrate possible alternatives for the therapy of pain. However, the COEFC presented more significant effects at lower doses than the isolated OEFC, where this action may be justified by the properties and advantages of the complexation. Full article

(This article belongs to the Special Issue Polymers in Nanocarrier Systems)

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10 pages, 3600 KiB

Open AccessArticle

Polymer-Derived Nitrogen-Doped Carbon Nanosheet Cluster and Its Application for Water Purification

by Xiaoyan Yu, Ting Zheng and Srikanth Pilla

Macromol 2021, 1(2), 84-93; https://doi.org/10.3390/macromol1020007 - 2 Apr 2021

Cited by 1 | Viewed by 2747

Abstract

A series of nitrogen-doped carbons (NCs) were prepared by the pyrolysis (300–900 °C) of crystalline polyazomethine (PAM) synthesized via a facile condensation reaction in methanol solvent. The controlled solvent evaporation resulted in PAM crystals in the form of nanosheet clusters with a sheet [...] Read more.

A series of nitrogen-doped carbons (NCs) were prepared by the pyrolysis (300–900 °C) of crystalline polyazomethine (PAM) synthesized via a facile condensation reaction in methanol solvent. The controlled solvent evaporation resulted in PAM crystals in the form of nanosheet clusters with a sheet thickness of ~50 nm. Such architecture was maintained after pyrolysis, obtaining porous CNs of high specific surface areas of up to 700 m²/g. The resulting NCs were used as absorbents to remove aromatic Rhodamine B from water. The NC that pyrolyzed at 750 °C exhibited the highest adsorption capacity (0.025 mg/mg), which is attributed to its high surface area and surface condition. Full article

(This article belongs to the Special Issue Polymer-Based Nanomaterials)

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20 pages, 5281 KiB

Open AccessReview

Chemical Functionalization of Carbon Nanotubes with Polymers: A Brief Overview

by Ana Maria Díez-Pascual

Macromol 2021, 1(2), 64-83; https://doi.org/10.3390/macromol1020006 - 30 Mar 2021

Cited by 101 | Viewed by 8030

Abstract

Carbon nanotubes (CNTs), the one-dimensional allotropes of carbon, have attracted noteworthy research interest since their discovery in 1991 owing to their large aspect ratio, low mass density, and unique chemical, physical, and electronic properties that provide exciting possibilities for nanoscale applications. Nonetheless, two [...] Read more.

Carbon nanotubes (CNTs), the one-dimensional allotropes of carbon, have attracted noteworthy research interest since their discovery in 1991 owing to their large aspect ratio, low mass density, and unique chemical, physical, and electronic properties that provide exciting possibilities for nanoscale applications. Nonetheless, two major issues should be considered when working with this sort of nanomaterial: their strong agglomerating tendency, since they are typically present as bundles or ropes of nanotubes, and the metallic impurities and carbonaceous fragments that go along with the CNTs. The successful utilization of CNTs in a wide variety of applications—in particular, in the field of polymer composites—depends on their uniform dispersion and the development of a strong chemical interaction with the polymeric matrix. To achieve these aims, chemical functionalization of their sidewalls and tips is required. In this article, a brief overview of the different approaches for CNT modification using polymers is provided, focusing on the covalent functionalization via “grafting to” or “grafting from” strategies. The characteristics and advantages of each approach are thoroughly discussed, including a few typical and recent examples. Moreover, applications of polymer-grafted CNTs as biosensors, membranes, energy storage substances, and EMI shielding are briefly described. Finally, future viewpoints in this vibrant research area are proposed. Full article

(This article belongs to the Special Issue Polymer-Based Nanomaterials)

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Macromol, Volume 1, Issue 2 (June 2021) – 7 articles

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