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1
Chabert, Emmanuelle, Laurent Chazeau, Catherine Gauthier, Rémy Dendievel et Jean-Yves Cavaillé. « Nanocomposites base polymère, renforcés par des particules rigides ». Mécanique & ; Industries 5, no 4 (juillet 2004) : 489–96. http://dx.doi.org/10.1051/meca:2004049.
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Guyot, A., R. Audebert, R. Botet, B. Cabane, F. Lafuma, R. Jullien, E. Pefferkorn, C. Pichot, A. Revillon et R. Varoqui. « Floculation de particules colloïdales par les polymères hydrosolubles ». Journal de Chimie Physique 87 (1990) : 1859–99. http://dx.doi.org/10.1051/jcp/1990871859.
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Guyot, A. « Synthèse de petites particules polymères sphérique de taille contrôlée ». Journal de Chimie Physique 84 (1987) : 1085–93. http://dx.doi.org/10.1051/jcp/1987841085.
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Kausar, Ayesha. « Potential of Polymer/Fullerene Nanocomposites for Anticorrosion Applications in the Biomedical Field ». Journal of Composites Science 6, no 12 (16 décembre 2022) : 394. http://dx.doi.org/10.3390/jcs6120394.
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Initially, this review presents the fundamentals of corrosion-resistant polymer/fullerene nanocomposites. Then, the potential of polymer/fullerene nanocomposites for corrosion resistance in biomedical applications is presented. In particular, anticorrosion biomedical applications of fullerene-based nanomaterials are proposed for antimicrobial applications, drug delivery, bioimaging, etc. According to the literature, due to the low conductivity/anticorrosion features of pristine thermoplastic polymers, conjugated polymers (polyaniline, polypyrrole, polythiophene, etc.) with high corrosion resistance performance were used. Subsequently, thermoplastic/thermosetting polymers were filled with nanoparticles to enhance their anticorrosion properties relative to those of neat polymers. Accordingly, fullerene-derived nanocomposites were found to be effective for corrosion protection. Polymer/fullerene nanocomposites with a fine dispersion and interactions revealed superior anticorrosion performance. The formation of a percolation network in the polymers/fullerenes facilitated their electron conductivity and, thus, corrosion resistance behavior. Consequently, the anticorrosion polymer/fullerene nanocomposites were applied in the biomedical field. However, this field needs to be further explored to see the full biomedical potential of anticorrosion polymer/fullerene nanocomposites.
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Nellithala, Dheeraj, Parin Shah et Paul Kohl. « (Invited) Durability and Accelerated Aging of Anion-Conducting Membranes and Ionomers ». ECS Meeting Abstracts MA2022-02, no 43 (9 octobre 2022) : 1606. http://dx.doi.org/10.1149/ma2022-02431606mtgabs.
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Low-temperature, polymer-based fuel cells and water electrolyzers using anion conductive polymers have several potential advantages over acid-based polymer electrolyzers. However, the long-term durability of the ion conducting polymer has not been investigated to the same extent as proton conducting polymers. Further, accelerated aging test conditions with known acceleration factors have not been developed. In this study, a family of poly(norbornene) polymers used in fuel cells and electrolyzers was aged under a variety of conditions to determine the aging rate and acceleration factors. In particular, the relationship between temperature, alkalinity, and time were investigated.
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Al-Obaidi, Hisham, Mridul Majumder et Fiza Bari. « Amorphous and Crystalline Particulates : Challenges and Perspectives in Drug Delivery ». Current Pharmaceutical Design 23, no 3 (20 février 2017) : 350–61. http://dx.doi.org/10.2174/1381612822666161107162109.
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Crystalline and amorphous dispersions have been the focus of academic and industrial research due to their potential role in formulating poorly water-soluble drugs. This review looks at the progress made starting with crystalline carriers in the form of eutectics moving towards more complex crystalline mixtures. It also covers using glassy polymers to maintain the drug as amorphous exhibiting higher energy and entropy. However, the amorphous form tends to recrystallize on storage, which limits the benefits of this approach. Specific interactions between the drug and the polymer may retard this spontaneous conversion of the amorphous drug. Some studies have shown that it is possible to maintain the drug in the amorphous form for extended periods of time. For the drug and the polymer to form a stable mixture they have to be miscible on a molecular basis. Another form of solid dispersions is pharmaceutical co-crystals, for which research has focused on understanding the chemistry, crystal engineering and physico-chemical properties. USFDA has issued a guidance in April 2013 suggesting that the co-crystals as a pharmaceutical product may be a reality; but just not yet! While some of the research is still oriented towards application of these carriers, understanding the mechanism by which drug-carrier miscibility occurs is also covered. Within this context is the use of thermodynamic models such as Flory-Huggins model with some examples of studies used to predict miscibility.
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Walton, Jeffrey H. « A Review of 129Xe NMR as a Probe of Polymer Morphology ». Engineering Plastics 2, no 1 (janvier 1994) : 147823919400200. http://dx.doi.org/10.1177/147823919400200105.
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129 Xe NMR is a new tool for probing the morphology of polymers and polymer blends. Recent developments of the NMR of 129 Xe gas dissolved in polymers are reviewed. This technique yields information on polymer morphology via the NMR lineshape and the isotropic chemical shift and their temperature dependencies. Polymer glass transition temperatures are plainly evident. The miscibility of polymer blends is easily determined and thus phase diagrams may be mapped out. Of particular use is the potential ability to measure domain sizes in immiscible polymer blends by 2-D NMR techniques. Domain sizes from 0.1 micrometers to 25 micrometers should easily be measurable.
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Walton, Jeffrey H. « A Review of 129Xe NMR as a Probe of Polymer Morphology ». Polymers and Polymer Composites 2, no 1 (janvier 1994) : 35–41. http://dx.doi.org/10.1177/096739119400200105.
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129 Xe NMR is a new tool for probing the morphology of polymers and polymer blends. Recent developments of the NMR of 129 Xe gas dissolved in polymers are reviewed. This technique yields information on polymer morphology via the NMR lineshape and the isotropic chemical shift and their temperature dependencies. Polymer glass transition temperatures are plainly evident. The miscibility of polymer blends is easily determined and thus phase diagrams may be mapped out. Of particular use is the potential ability to measure domain sizes in immiscible polymer blends by 2-D NMR techniques. Domain sizes from 0.1 micrometers to 25 micrometers should easily be measurable.
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Shin, Dong Sig, Jae Hoon Lee et Jeong Suh. « Microfabrication of Polymers Using KrF Excimer Laser Beam ». Key Engineering Materials 326-328 (décembre 2006) : 115–18. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.115.
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Pulsed UV laser beams, which are widely used in the processing of polymers, offer many advantages in the field of polymer production, primarily because their photon energy is higher than the binding energy of the polymer. In particular, the fabrication of polymers with an excimer laser process is faster and more convenient than with other processes. Nevertheless, some problems occur in the precision microprocessing of polymers, including the formation and deposition of surface debris, which is produced from the breakdown of either polymer chains or radical bonds. In the present work, a process for eliminating carbonized surface debris contamination generated by the laser ablation of a polymer was developed. The proposed approach for removing surface debris utilizes an erasable ink pasted on the polymer. The surface debris ejected from the polymer is then combined with the ink layer on the polymer. Finally, both the surface debris and the ink layer can be removed using adhesive tape.
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Günther, Roman, Walter Caseri et Christof Brändli. « Application of Atmospheric-Pressure Jet Plasma in the Presence of Acrylic Acid for Joining Polymers without Adhesives ». Materials 16, no 7 (28 mars 2023) : 2673. http://dx.doi.org/10.3390/ma16072673.
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This study investigates the treatment of surfaces with jet plasma at atmospheric pressure in the presence of acrylic acid as a resource-saving and efficient approach to joining polymers on polystyrene (PS) and polyamide 12 (PA 12) surfaces. Acrylic acid was added in order to introduce functional groups to the polymer surfaces. XPS analysis revealed a high density of oxygen-containing groups, e.g., carboxylic acid groups, on the polymer surfaces, the detailed composition depending on the polymer. The AFM measurements indicated that the modification of polyamide resulted in morphological changes and an increase in surface roughness due to polymer recrystallization. When the surface-modified polymers were brought in contact under a load, significant adhesion between the polymer surfaces was measured. In particular, PS and PA 12, which are otherwise difficult to join by gluing, could readily be connected in this way. The joint polymers could be separated intentionally by immersion in water, thus enabling the recycling of the materials. The resistance of the joint to water depends on the polymer system, with polyamide providing strikingly higher resistance than polystyrene. Accordingly, treating the joint polymers with water allows debonding on demand, particularly when PS is involved. Exposure of modified polymer surfaces to solutions of metal ions increased the resistance of joint polymers to water.
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Wang, Jinfang, Peter A. G. Cormack, David C. Sherrington et Ezat Khoshdel. « Synthesis and characterization of micrometer-sized molecularly imprinted spherical polymer particulates prepared via precipitation polymerization ». Pure and Applied Chemistry 79, no 9 (1 janvier 2007) : 1505–19. http://dx.doi.org/10.1351/pac200779091505.
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In this paper, the synthesis and characterization of molecularly imprinted spherical polymer particulates prepared via precipitation polymerization is described. The effects of the monomer and initiator concentrations and the solvent on the polymerizations were investigated systematically. Polymer microspheres with narrow size distributions and average diameters up to ca. 10 μm were prepared under optimized polymerization conditions. The morphologies of the microspheres were characterized by nitrogen sorption porosimetry and the molecular recognition properties of representative products evaluated in high-performance liquid chromatography (HPLC) mode. Imprinting effects were confirmed by analyzing the relative retentions of the analytes on imprinted and non-imprinted packed HPLC columns. Finally, two different agitation/mixing methods for precipitation polymerizations were compared. It was found that the use of a low-profile roller housed inside a temperature-controlled incubator had advantages over a rotavapor-based system. Overall, this study has served to highlight the attractiveness of precipitation polymerization for the routine production of molecularly imprinted polymers in a well-defined spherical particulate form via an efficient one-step synthetic process.
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Liu, Guifeng, Xudong Sun, Xiaodong Li et Zhenxin Wang. « The Bioanalytical and Biomedical Applications of Polymer Modified Substrates ». Polymers 14, no 4 (21 février 2022) : 826. http://dx.doi.org/10.3390/polym14040826.
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Polymers with different structures and morphology have been extensively used to construct functionalized surfaces for a wide range of applications because the physicochemical properties of polymers can be finely adjusted by their molecular weights, polydispersity and configurations, as well as the chemical structures and natures of monomers. In particular, the specific functions of polymers can be easily achieved at post-synthesis by the attachment of different kinds of active molecules such as recognition ligand, peptides, aptamers and antibodies. In this review, the recent advances in the bioanalytical and biomedical applications of polymer modified substrates were summarized with subsections on functionalization using branched polymers, polymer brushes and polymer hydrogels. The review focuses on their applications as biosensors with excellent analytical performance and/or as nonfouling surfaces with efficient antibacterial activity. Finally, we discuss the perspectives and future directions of polymer modified substrates in the development of biodevices for the diagnosis, treatment and prevention of diseases.
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Kaur, Harmeet, Virender Kumar, Krishan Kumar, Sandeep Rathor, Parveen Kumari et Jasbir Singh. « Polymer Particulates in Drug Delivery ». Current Pharmaceutical Design 22, no 19 (10 mai 2016) : 2761–87. http://dx.doi.org/10.2174/1381612822666160217125734.
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Quezada, Gonzalo R., Norman Toro, Jorge Saavedra, Pedro Robles, Iván Salazar, Alessandro Navarra et Ricardo I. Jeldres. « Molecular Dynamics Study of the Conformation, Ion Adsorption, Diffusion, and Water Structure of Soluble Polymers in Saline Solutions ». Polymers 13, no 20 (14 octobre 2021) : 3550. http://dx.doi.org/10.3390/polym13203550.
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Polymers have interesting physicochemical characteristics such as charge density, functionalities, and molecular weight. Such attributes are of great importance for use in industrial purposes. Understanding how these characteristics are affected is still complex, but with the help of molecular dynamics (MD) and quantum calculations (QM), it is possible to understand the behavior of polymers at the molecular level with great consistency. This study was applied to polymers derived from polyacrylamide (PAM) due to its great use in various industries. The polymers studied include hydrolyzed polyacrylamide (HPAM), poly (2-acrylamido-2-methylpropanesulfonate) (PAMPS), polyacrylic acid (PAA), polyethylene oxide polymer (PEO), and guar gum polysaccharide (GUAR). Each one has different attributes, which help in understanding the effects on the polymer and the medium in which it is applied along a broad spectrum. The results include the conformation, diffusion, ion condensation, the structure of the water around the polymer, and interatomic polymer interactions. Such characteristics are important to selecting a polymer depending on the environment in which it is found and its purpose. The effect caused by salinity is particular to each polymer, where polymers with an explicit charge or polyelectrolytes are more susceptible to changes due to salinity, increasing their coiling and reducing their mobility in solution. This naturally reduces its ability to form polymeric bridges due to having a polymer with a smaller gyration radius. In contrast, neutral polymers are less affected in their structure, making them favorable in media with high ionic charges.
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Yan, Haotian. « Synthetic Route And Application of Photodegradable Polymers ». Highlights in Science, Engineering and Technology 21 (4 décembre 2022) : 324–31. http://dx.doi.org/10.54097/hset.v21i.3187.
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With the accumulating mass of land wastes, designing end-of-life principles for plastic wastes is becoming one of the most debated topics for polymer scientists. A developing family of materials called photodegradable polymers carries great environmental and commercial values. Photodegradable polymers will engage in photolysis under specific wavelengths, resulting in cleavages on the polymer backbone and smaller molecular weights. This research will discuss standard methods of photodegradation, such as Norris I&II, along with common photodegradable polymers and their functionalities. Examples of photodegradable polymers illustrated are polybutadiene, isotactic poly(propylene oxide) (iPPO), polylactide (PLA), and polystyrene. In Particular, this research used polystyrene as an example to explain the common degradation steps of photodegradable polymers. Nevertheless, the synthetic route and plans utilized for those polymers are discussed, shedding light on future possibilities in this field. Promising directions, such as metal-organic polymers with metal-to-metal bonds that can be synthesized through ring-opening metathesis polymerization (ROMP) are touched upon by the end of the research, introducing possible future implications in polymer science.
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He, Yuanxin, Hongyu Li, Xiang Xiao et Xinyu Zhao. « Polymer Degradation : Category, Mechanism and Development Prospect ». E3S Web of Conferences 290 (2021) : 01012. http://dx.doi.org/10.1051/e3sconf/202129001012.
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With the increasing demand for polymers, white pollution has become a serious concern all around the world. The admirable degradation methods of them are desirable for overcoming this problem. In the past several decades, numerous researches on polymer degradation have been reported. This review commits to different degradation strategies of polymers and four main degradation protocols firstly, including photodegradation, oxidative degradation, catalytic degradation, and biodegradation, are demonstrated in detail. Secondly, some specific samples are discussed for each kind of degradation. Finally, the outlook and future of polymer degradation are proposed. In particular, the comprehensive comparison of different degradation methods is covered to provide the best choice for dealing with different polymers wastes. These will be beneficial to the development of processing plastic and conversion of polymer wastes.
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Rymuza, Zygmunt, Zbigniew Kusznierewicz et Grzegorz Mańturzyk. « Testing miniature, in particular polymer-polymer, journal bearings ». Wear 174, no 1-2 (mai 1994) : 39–46. http://dx.doi.org/10.1016/0043-1648(94)90084-1.
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Romano, Angelo, Ignazio Roppolo, Elisabeth Rossegger, Sandra Schlögl et Marco Sangermano. « Recent Trends in Applying Ortho-Nitrobenzyl Esters for the Design of Photo-Responsive Polymer Networks ». Materials 13, no 12 (19 juin 2020) : 2777. http://dx.doi.org/10.3390/ma13122777.
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Polymers with light-responsive groups have gained increased attention in the design of functional materials, as they allow changes in polymers properties, on demand, and simply by light exposure. For the synthesis of polymers and polymer networks with photolabile properties, the introduction o-nitrobenzyl alcohol (o-NB) derivatives as light-responsive chromophores has become a convenient and powerful route. Although o-NB groups were successfully exploited in numerous applications, this review pays particular attention to the studies in which they were included as photo-responsive moieties in thin polymer films and functional polymer coatings. The review is divided into four different sections according to the chemical structure of the polymer networks: (i) acrylate and methacrylate; (ii) thiol-click; (iii) epoxy; and (iv) polydimethylsiloxane. We conclude with an outlook of the present challenges and future perspectives of the versatile and unique features of o-NB chemistry.
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Pawlak, Andrzej, et Justyna Krajenta. « Progress in Studies of Disentangled Polymers and Composites ». Journal of Composites Science 7, no 12 (18 décembre 2023) : 521. http://dx.doi.org/10.3390/jcs7120521.
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Macromolecule entanglements are common in polymers. The first part of this review describes their influence on the properties of entangled polymers. Then, methods for reducing the entanglement density of macromolecule chains are discussed. It has been shown that research on partially disentangled polymers has provided a lot of new information about the relationship between the entangled state and properties of polymers. This research concerns, among others, mechanical and thermal properties and the crystallization process. A special disentangled polymer case, ultra-high-molecular-weight polyethylene, is also discussed. The results of research on polymer composites in which macromolecules were disentangled via processing and composites were produced using already disentangled polymers are presented in particular detail. It has been indicated that such composites and blends of disentangled polymers are promising and will probably be intensively researched in the near future.
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BONDARUK, O. M., et L. V. KARABANOVA. « NANOCOMPOSITES BASED ON SINGLECOMPONENT AND MULTICOMPONENT POLYMER MATRICES FOR BIOMEDICAL APPLICATIONS ». Polymer journal 44, no 1 (1 mai 2022) : 3–23. http://dx.doi.org/10.15407/polymerj.44.01.003.
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The review is devoted to analysis of the publications in the area of polymers of biomedical applications. Different types of the polymer matrices for drug delivery are analyzed, including polyurethanes, hydroxyacrylates, and multicomponent polymer matrices, which created by method of interpenetrating polymer networks. Particular attention is paid to description of synthesized and investigated nanocomposites based on polyurethane / poly (2-hydroxyethyl methacrylate) polymer matrix and nanooxides modified by biologically active compounds.
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Chremos, Alexandros, et Jack F. Douglas. « Influence of Branching on the Configurational and Dynamical Properties of Entangled Polymer Melts ». Polymers 11, no 6 (14 juin 2019) : 1045. http://dx.doi.org/10.3390/polym11061045.
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We probe the influence of branching on the configurational, packing, and density correlation function properties of polymer melts of linear and star polymers, with emphasis on molecular masses larger than the entanglement molecular mass of linear chains. In particular, we calculate the conformational properties of these polymers, such as the hydrodynamic radius R h , packing length p, pair correlation function g ( r ) , and polymer center of mass self-diffusion coefficient, D, with the use of coarse-grained molecular dynamics simulations. Our simulation results reproduce the phenomenology of simulated linear and branched polymers, and we attempt to understand our observations based on a combination of hydrodynamic and thermodynamic modeling. We introduce a model of “entanglement” phenomenon in high molecular mass polymers that assumes polymers can viewed in a coarse-grained sense as “soft” particles and, correspondingly, we model the emergence of heterogeneous dynamics in polymeric glass-forming liquids to occur in a fashion similar to glass-forming liquids in which the molecules have soft repulsive interactions. Based on this novel perspective of polymer melt dynamics, we propose a functional form for D that can describe our simulation results for both star and linear polymers, covering both the unentangled to entangled polymer melt regimes.
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Brostow, Witold, et Haley E. Hagg Lobland. « Survey of Relations of Chemical Constituents in Polymer-Based Materials with Brittleness and its Associated Properties ». Chemistry & ; Chemical Technology 10, no 4s (25 décembre 2016) : 595–600. http://dx.doi.org/10.23939/chcht10.04si.595.
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The property of brittleness for polymers and polymer-based materials (PBMs) is an important factor in determining the potential uses of a material. Brittleness of polymers may also impact the ease and modes of polymer processing, thereby affecting economy of production. Brittleness of PBMs can be correlated with certain other properties and features of polymers; to name a few, connections to free volume, impact strength, and scratch recovery have been explored. A common thread among all such properties is their relationship to chemical composition and morphology. Through a survey of existing literature on polymer brittleness specifically combined with relevant reports that connect additional materials and properties to that of brittleness, it is possible to identify chemical features of PBMs that are connected with observable brittle behavior. Relations so identified between chemical composition and structure of PBMs and brittleness are described herein, advancing knowledge and improving the capacity to design new and to choose among existing polymers in order to obtain materials with particular property profiles.
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Myshkin, Nikolai K., et Alexander Kovalev. « Polymer mechanics and tribology ». Industrial Lubrication and Tribology 70, no 4 (8 mai 2018) : 764–72. http://dx.doi.org/10.1108/ilt-06-2017-0162.
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Purpose The purpose of this paper is to review the advances in mechanics and tribology of polymers and polymer-based materials. It is focused on the understanding of the correlation of contact mechanics and the tribological behavior of polymers and polymer composites by taking account of surface forces and adhesion in the contact. Design/methodology/approach Mechanical behavior of polymers is considered a viscoelasticity. Tribological performance is estimated while considering the parts of deformation and adhesion in friction arising in the contact. Surface energy, roughness, load and temperature effects on the tribological behavior of polymers are evaluated. Polymer composites produced by reinforcing and by the addition of functional additives are considered as materials for various applications in tribology. Particular attention is given to polymer-based nanocomposites. Findings A review of studies in tribology has shown that polymer-based materials can be most successfully used as self-lubricating components of sliding bearings. The use of the fillers provides changes in the tribological performance of neat polymers and widens their areas of application in the industry. Thin polymer films were found to be prospective lubricants for memory storage devices, micro-electro-mechanical systems and precision mechanisms. Further progress in polymer tribology should be achieved on solving the problems of contact mechanics, surface physics and tribochemistry by taking account of the scale factor. Originality/value The review is based on the experience of the authors in polymer mechanics and tribology, their research data and on data of many other literature sources published in this area. It can be useful for specialists in polymer research and industrial engineers working in tribology and industrial lubrication.
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Flemming, Patricia, Alexander S. Münch, Andreas Fery et Petra Uhlmann. « Constrained thermoresponsive polymers – new insights into fundamentals and applications ». Beilstein Journal of Organic Chemistry 17 (20 août 2021) : 2123–63. http://dx.doi.org/10.3762/bjoc.17.138.
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In the last decades, numerous stimuli-responsive polymers have been developed and investigated regarding their switching properties. In particular, thermoresponsive polymers, which form a miscibility gap with the ambient solvent with a lower or upper critical demixing point depending on the temperature, have been intensively studied in solution. For the application of such polymers in novel sensors, drug delivery systems or as multifunctional coatings, they typically have to be transferred into specific arrangements, such as micelles, polymer films or grafted nanoparticles. However, it turns out that the thermodynamic concept for the phase transition of free polymer chains fails, when thermoresponsive polymers are assembled into such sterically confined architectures. Whereas many published studies focus on synthetic aspects as well as individual applications of thermoresponsive polymers, the underlying structure–property relationships governing the thermoresponse of sterically constrained assemblies, are still poorly understood. Furthermore, the clear majority of publications deals with polymers that exhibit a lower critical solution temperature (LCST) behavior, with PNIPAAM as their main representative. In contrast, for polymer arrangements with an upper critical solution temperature (UCST), there is only limited knowledge about preparation, application and precise physical understanding of the phase transition. This review article provides an overview about the current knowledge of thermoresponsive polymers with limited mobility focusing on UCST behavior and the possibilities for influencing their thermoresponsive switching characteristics. It comprises star polymers, micelles as well as polymer chains grafted to flat substrates and particulate inorganic surfaces. The elaboration of the physicochemical interplay between the architecture of the polymer assembly and the resulting thermoresponsive switching behavior will be in the foreground of this consideration.
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Chremos, Alexandros, et Ferenc Horkay. « Comparison of neutral and charged polyelectrolyte bottlebrush polymers in dilute salt-free conditions ». MRS Advances 5, no 17 (2020) : 899–906. http://dx.doi.org/10.1557/adv.2020.9.
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ABSTRACTWe investigate the structure of neutral and charged bottlebrush polymers in salt-free solutions at different polymer concentrations. In particular, we use molecular dynamics simulations by utilizing a coarse-grained bead-spring model that includes an explicit solvent and complementary experiments made by small angle neutron scattering (SANS). We find that the charged groups along the side chains exert significant repulsive forces, resulting in polymer swelling and backbone stretching. In addition to the primary polyelectrolyte peak, we find that bottlebrush polymers exhibit an additional peak in the form and static structure factors, a feature that is absent in neutral polymers. We show that this additional peak describes the intra-molecular correlations between the charged side chains.
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Hu, Jinming, Ruirui Qiao, Michael R. Whittaker, John F. Quinn et Thomas P. Davis. « Synthesis of Star Polymers by RAFT Polymerization as Versatile Nanoparticles for Biomedical Applications ». Australian Journal of Chemistry 70, no 11 (2017) : 1161. http://dx.doi.org/10.1071/ch17391.
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The precise control of polymer chain architecture has been made possible by developments in polymer synthesis and conjugation chemistry. In particular, the synthesis of polymers in which at least three linear polymeric chains (or arms) are tethered to a central core has yielded a useful category of branched architecture, so-called star polymers. Fabrication of star polymers has traditionally been achieved using either a core-first technique or an arm-first approach. Recently, the ability to couple polymeric chain precursors onto a functionalized core via highly efficient coupling chemistry has provided a powerful new methodology for star synthesis. Star syntheses can be implemented using any of the living polymerization techniques using ionic or living radical intermediates. Consequently, there are innumerable routes to fabricate star polymers with varying chemical composition and arm numbers. In comparison with their linear counterparts, star polymers have unique characteristics such as low viscosity in solution, prolonged blood circulation, and high accumulation in tumour regions. These advantages mean that, far beyond their traditional application as rheology control agents, star polymers may also be useful in the medical and pharmaceutical sciences. In this account, we discuss recent advances made in our laboratory focused on star polymer research ranging from improvements in synthesis through to novel applications of the product materials. Specifically, we examine the core-first and arm-first preparation of stars using reversible addition–fragmentation chain transfer (RAFT) polymerization. Further, we also discuss several biomedical applications of the resulting star polymers, particularly those made by the arm-first protocol. Emphasis is given to applications in the emerging area of nanomedicine, in particular to the use of star polymers for controlled delivery of chemotherapeutic agents, protein inhibitors, signalling molecules, and siRNA. Finally, we examine possible future developments for the technology and suggest the further work required to enable clinical applications of these interesting materials.
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Crespy, Daniel, et Katharina Landfester. « Miniemulsion polymerization as a versatile tool for the synthesis of functionalized polymers ». Beilstein Journal of Organic Chemistry 6 (1 décembre 2010) : 1132–48. http://dx.doi.org/10.3762/bjoc.6.130.
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The miniemulsion technique is a particular case in the family of heterophase polymerizations, which allows the formation of functionalized polymers by polymerization or modification of polymers in stable nanodroplets. We present here an overview of the different polymer syntheses within the miniemulsion droplets as reported in the literature, and of the current trends in the field.
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Tanaka, Tomonari. « Recent Advances in Polymers Bearing Activated Esters for the Synthesis of Glycopolymers by Postpolymerization Modification ». Polymers 16, no 8 (15 avril 2024) : 1100. http://dx.doi.org/10.3390/polym16081100.
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Glycopolymers are functional polymers with saccharide moieties on their side chains and are attractive candidates for biomaterials. Postpolymerization modification can be employed for the synthesis of glycopolymers. Activated esters are useful in various fields, including polymer chemistry and biochemistry, because of their high reactivity and ease of reaction. In particular, the formation of amide bonds caused by the reaction of activated esters with amino groups is of high synthetic chemical value owing to its high selectivity. It has been employed in the synthesis of various functional polymers, including glycopolymers. This paper reviews the recent advances in polymers bearing activated esters for the synthesis of glycopolymers by postpolymerization modification. The development of polymers bearing hydrophobic and hydrophilic activated esters is described. Although water-soluble activated esters are generally unstable and hydrolyzed in water, novel polymer backbones bearing water-soluble activated esters are stable and useful for postpolymerization modification for synthesizing glycopolymers in water. Dual postpolymerization modification can be employed to modify polymer side chains using two different molecules. Thiolactone and glycine propargyl esters on the polymer backbone are described as activated esters for dual postpolymerization modification.
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Grob, Lucas, Liridon Zeneli, Eileen Ott, Jacopo Vialetto, Jotam Bergfreund, Yasushi Takeda et Erich J. Windhab. « Filter-less separation technique for micronized anthropogenic polymers from artificial seawater ». Environmental Science : Water Research & ; Technology 7, no 12 (2021) : 2372–80. http://dx.doi.org/10.1039/d1ew00553g.
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Anthropogenic polymer particulates (APPs) are a highly researched topic, from the identification of their different sources to their impact on living organisms, and micronized anthropogenic polymers pose a threat to many ecosystems.
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Galuska, Alan A. « Atomic Force Microscopy of Industrial Polymers ». Microscopy and Microanalysis 5, S2 (août 1999) : 982–83. http://dx.doi.org/10.1017/s1431927600018237.
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The performance of many industrial polymers is determined by the microscopic morphology of the polymers. For example, surface morphology can influence properties such as adhesion, friction, sealing, blocking, printability, wettability, and haze. Furthermore, bulk morphology often controls mechanical properties such as toughness. strength, wear, and tear resistance. In order to optimize polymer performance, quick reliable methods of determining surface and bulk morphology are essential.In the past, electron microscopy (in particular TEM) has been the primary method for determining polymer morphology. However, the usefulness of electron microscopy has been limited by the destructive nature of the electron beam, the naturally poor contrast between polymer types, and the difficulty in preparing (staining, etching, cryogenic ultramicrotoming, etc.) high quality specimens.Recently, the tapping phase-shift mode of atomic force microscopy (TPSAFM) has provided the polymer scientist with a simple, quick, flexible and quantitative method for determining polymer surface and bulk morphology.
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Motoyanagi, Jin, Ayane Fujishima et Masahiko Minoda. « Controlled Synthesis and Photoresponsive Properties of Spiropyran End-Functionalized Poly(vinyl ether)s ». Crystals 12, no 5 (22 mai 2022) : 742. http://dx.doi.org/10.3390/cryst12050742.
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Due to the need to develop smart materials for a variety of applications such as catalysts and drug delivery, the development of photoresponsive polymers is receiving increasing attention. In particular, the photoisomerization of spiropyran (SP), unlike many other photoresponsive compounds, has attracted attention because it dramatically changes not only the molecular structure but also the polarity of the molecule. However, in most cases where SP is used as a photoresponsive functional group, SP is introduced in the side chain of the polymer, and few cases have been reported in which SP is introduced at the end of the polymer chain. Therefore, we designed a new amphipathic poly(vinyl ether) with an SP moiety at the end of the polymer chain. First, an initiator having an SP moiety was synthesized and used for living cationic polymerization to synthesize a poly(vinyl ether) bearing an SP moiety at the end of the polymer chain. Furthermore, we investigated the photoresponsive properties of the obtained polymers, we found that self-assembly of the amphiphilic polymers could be controlled by photoirradiation.
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Arrigo, Rossella, Giulio Malucelli et Francesco Paolo La Mantia. « Effect of the Elongational Flow on the Morphology and Properties of Polymer Systems : A Brief Review ». Polymers 13, no 20 (14 octobre 2021) : 3529. http://dx.doi.org/10.3390/polym13203529.
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Polymer-processing operations with dominating elongational flow have a great relevance, especially in several relevant industrial applications. Film blowing, fiber spinning and foaming are some examples in which the polymer melt is subjected to elongational flow during processing. To gain a thorough knowledge of the material-processing behavior, the evaluation of the rheological properties of the polymers experiencing this kind of flow is fundamental. This paper reviews the main achievements regarding the processing-structure-properties relationships of polymer-based materials processed through different operations with dominating elongational flow. In particular, after a brief discussion on the theoretical features associated with the elongational flow and the differences with other flow regimes, the attention is focused on the rheological properties in elongation of the most industrially relevant polymers. Finally, the evolution of the morphology of homogeneous polymers, as well as of multiphase polymer-based systems, such as blends and micro- and nano-composites, subjected to the elongational flow is discussed, highlighting the potential and the unique characteristics of the processing operations based on elongation flow, as compared to their shear-dominated counterparts.
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Engler, Anthony, Jared Schwartz et Paul Kohl. « (Student Award, 1st Place, Invited) Rapid Nanometer Scale Patterning Using New High-Sensitivity, Dry-Develop Resists ». ECS Meeting Abstracts MA2022-02, no 18 (9 octobre 2022) : 867. http://dx.doi.org/10.1149/ma2022-0218867mtgabs.
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A family of high-resolution, photo-thermal resists based on low ceiling temperature copolymers has been developed and used in a nanometer scale, direct-write thermal patterning tool. The polymer resists are composed of cyclic, low ceiling temperature (Tc) poly(aldehydes). Tc is the thermodynamic temperature which separates polymer from monomer. The Tc of the polymers is below room temperature making the polymer meta-stable at room temperature. The resists very rapidly and cleanly decompose into monomer only when triggered during patterning because the mechanism of depolymerization is suppressed. Cleaving a single bond in the polymer chain initiates the spontaneous and complete depolymerization of the polymer. The use of these low Tc polymers in thermal scanning probe lithography to resolve nanometer size features will be described. Laser ablation of the same polymers has been demonstrated in thermal scanning probe tools allowing for the rapid removal of large areas of the resist adding speed to the hot-tip thermal patterning capability. A particular advantage of the laser assisted thermal scanning probe patterning tools is the ability to form three-dimensional features both by hot-tip patterning and laser ablation.
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Klimenko, O. N., M. I. Valueva et A. N. Rybnikova. « POLYMERS AND POLYMER COMPOSITES IN SPORT (review) ». Proceedings of VIAM, no 10 (2020) : 81–89. http://dx.doi.org/10.18577/2307-6046-2020-0-10-81-89.
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Рrovides an overview of scientific and technical information – Russian and foreign periodicals, patents for inventions – in the field of the use of polymeric materials in the sports industry and sports infrastructure. Data on world manufacturers, applied technologies, Russian developments in this direction are presented, examples of the practical use of polymeric materialsin the sports industry are shown. Special attention is paid to polymer composite materials,in particular, based on carbon fibers.
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Nadareishvili, Levan, Roland Bakuradze, Jimsher Aneli, Manana Areshidze, Ineza Pavlenishvili, Liana Sharashidze et Giorgi Basilaia. « Method and Mathematical Modeling of Formation of Gradually and Homogeneously Oriented Linear Polymers ». International Journal of Polymer Science 2019 (25 novembre 2019) : 1–11. http://dx.doi.org/10.1155/2019/8132518.
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Previously, we developed several technical solutions for the conversion of isotropic polymers into materials of a new type—gradually oriented polymers with a gradient of physical and mechanical properties, thereby materializing for the first time the unused possibilities inherent in the polymeric nature of the substance. The scientific basis of these developments is the concept of a new structural state of linear polymers—a gradually oriented (stretched) state (GOS), the essence of which is set out briefly. An algorithm and a mathematical model for controlling the process of uniaxial, zonal stretching of linear polymers are proposed, which allow the formation of gradually or homogeneously oriented polymers (polymer composites). At the same time, specified values of quantitative parameters are ensured, in particular, the selected profile of distribution of the relative elongation (linear, sinusoidal, etc.) along the length of the gradually oriented polymer sample and the specified constant relative elongation along the length of the homogeneously oriented polymer. Mathematical expressions for calculating the conditions to obtain gradually oriented polymers with given geometric dimensions (length, width) and with a given distribution of relative elongation along the length of the resulting sample were also derived. The description of method and principles of operation of the appropriate device is given. Experimental data illustrating the possibilities of the proposed method and the efficiency of mathematical modeling are presented. The issues of creating functionally graded materials with a gradient of microstructure (gradient of degree of orientation/relative elongation) or chemical composition (volume fraction of functional fillers), respectively, based on thermoplastic polymer/copolymer or polymer composite (containing functional fillers) by method of uniaxial, zonal graded stretching are discussed.
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Trhlíková, Olga, Sviatoslav Hladyš, Jan Sedláček et Dmitrij Bondarev. « SEC-DAD - Effective Method for the Characterization of π-Conjugated Polymers ». Materials Science Forum 851 (avril 2016) : 167–72. http://dx.doi.org/10.4028/www.scientific.net/msf.851.167.
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In the article we present a unique analytical tool for the characterization of conjugated polymers – SEC-DAD (Size Exclusion Chromatography – Diode Array Detector). The chromatographic separation is performed in a conventional SEC mode which provides narrow molecular-weight fractions of the analyzed polymer. The uniqueness of the SEC-DAD combination comes out with the utilization of DAD for the monitoring the absorption characteristics of particular fractions along the molecular weight distribution. If applied in the characterization of the conjugated polymers, SEC-DAD helps to reveal the dependencies of (i) the extent of conjugation and (ii) covalent and configuration structure of the polymer on the molecular weight.
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Głuszewski, Wojciech, Andrzej Stasiek, Aneta Raszkowska-Kaczor et Daniel Kaczor. « Effect of polyethylene cross-linking on properties of foams ». Nukleonika 63, no 3 (1 septembre 2018) : 81–85. http://dx.doi.org/10.2478/nuka-2018-0010.
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Abstract The process of cross-linking of polyethylene using gamma radiation (γ) and electron beam (EB) was tested from the point of view of density of foam. Particular attention was paid to the postradiation oxidation effect of the polymers. The study used two types of radiation sources of varying dose rates: gamma radiation (4 kGy/h) and EB (14 000 kGy/h). Radiolysis studies of the polymers used the radiation yield of hydrogen evolved (GH2, approximately proportional to the number of radicals) and radiation yield of oxygen absorbed by the polymer (GO2). Oxidation of polymer due to radiation was also evaluated using diffuse reflectance spectroscopy.
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Tawade, Pratik, Nimisha Tondapurkar et Akash Jangale. « Biodegradable and biocompatible synthetic polymers for applications in bone and muscle tissue engineering ». Journal of Medical Science 91, no 3 (30 septembre 2022) : e712. http://dx.doi.org/10.20883/medical.e712.
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In medicine, tissue engineering has made significant advances. Using tissue engineering techniques, transplant treatments result in less donor site morbidity and need fewer surgeries overall. It is now possible to create cell-supporting scaffolds that degrade as new tissue grows on them, replacing them until complete body function is restored. Synthetic polymers have been a significant area of study for biodegradable scaffolds due to their ability to provide customizable biodegradable and mechanical features as well as a low immunogenic effect due to biocompatibility. The food and drug administration has given the biodegradable polymers widespread approval after they showed their reliability. In the context of tissue engineering, this paper aims to deliver an overview of the area of biodegradable and biocompatible synthetic polymers. Frequently used synthetic biodegradable polymers utilized in tissue scaffolding, scaffold specifications, polymer synthesis, degradation factors, as well as fabrication methods are discussed. In order to emphasize the many desired properties and corresponding needs for skeletal muscle and bone, particular examples of synthetic polymer scaffolds are investigated. Increased biocompatibility, functionality and clinical applications will be made possible by further studies into novel polymer and scaffold fabrication approaches.
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Chrószcz-Porębska, Marta, et Agnieszka Gadomska-Gajadhur. « Cysteine Conjugation : An Approach to Obtain Polymers with Enhanced Muco- and Tissue Adhesion ». International Journal of Molecular Sciences 25, no 22 (13 novembre 2024) : 12177. http://dx.doi.org/10.3390/ijms252212177.
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The modification of polymers towards increasing their biocompatibility gathers the attention of scientists worldwide. Several strategies are used in this field, among which chemical post-polymerization modification has recently been the most explored. Particular attention revolves around polymer-L-cysteine (Cys) conjugates. Cys, a natural amino acid, contains reactive thiol, amine, and carboxyl moieties, allowing hydrogen bond formation and improved tissue adhesion when conjugated to polymers. Conjugation of Cys and its derivatives to polymers has been examined mostly for hyaluronic acid, chitosan, alginate, polyesters, polyurethanes, poly(ethylene glycol), poly(acrylic acid), polycarbophil, and carboxymethyl cellulose. It was shown that the conjugation of Cys and its derivatives to polymers significantly increased their tissue adhesion, particularly mucoadhesion, stability at physiological pH, drug encapsulation efficiency, drug release, and drug permeation. Conjugates were also non-toxic toward various cell lines. These properties make Cys conjugation a promising strategy for advancing polymer applications in drug delivery systems and tissue engineering. This review aims to provide an overview of these features and to present the conjugation of Cys and its derivatives as a modern and promising approach for enhancing polymer tissue adhesion and its application in the medical field.
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Shemwell, Brooke E., et Yiannis A. Levendis. « Particulates Generated from Combustion of Polymers (Plastics) ». Journal of the Air & ; Waste Management Association 50, no 1 (janvier 2000) : 94–102. http://dx.doi.org/10.1080/10473289.2000.10463994.
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González-Henríquez, Carmen, Mauricio Sarabia-Vallejos et Juan Rodríguez Hernandez. « Antimicrobial Polymers for Additive Manufacturing ». International Journal of Molecular Sciences 20, no 5 (10 mars 2019) : 1210. http://dx.doi.org/10.3390/ijms20051210.
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Three-dimensional (3D) printing technologies can be widely used for producing detailed geometries based on individual and particular demands. Some applications are related to the production of personalized devices, implants (orthopedic and dental), drug dosage forms (antibacterial, immunosuppressive, anti-inflammatory, etc.), or 3D implants that contain active pharmaceutical treatments, which favor cellular proliferation and tissue regeneration. This review is focused on the generation of 3D printed polymer-based objects that present antibacterial properties. Two main different alternatives of obtaining these 3D printed objects are fully described, which employ different polymer sources. The first one uses natural polymers that, in some cases, already exhibit intrinsic antibacterial capacities. The second alternative involves the use of synthetic polymers, and thus takes advantage of polymers with antimicrobial functional groups, as well as alternative strategies based on the modification of the surface of polymers or the elaboration of composite materials through adding certain antibacterial agents or incorporating different drugs into the polymeric matrix.
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Bao, Yinyin. « Controlling Molecular Aggregation-Induced Emission by Controlled Polymerization ». Molecules 26, no 20 (16 octobre 2021) : 6267. http://dx.doi.org/10.3390/molecules26206267.
Texte intégralRésumé :
In last twenty years, the significant development of AIE materials has been witnessed. A number of small molecules, polymers and composites with AIE activity have been synthesized, with some of these exhibiting great potential in optoelectronics and biomedical applications. Compared to AIE small molecules, macromolecular systems—especially well-defined AIE polymers—have been studied relatively less. Controlled polymerization methods provide the efficient synthesis of well-defined AIE polymers with varied monomers, tunable chain lengths and narrow dispersity. In particular, the preparation of single-fluorophore polymers through AIE molecule-initiated polymerization enables the systematic investigation of the structure–property relationships of AIE polymeric systems. Here, the main polymerization techniques involved in these polymers are summarized and the key parameters that affect their photophysical properties are analyzed. The author endeavored to collect meaningful information from the descriptions of AIE polymer systems in the literature, to find connections by comparing different representative examples, and hopes eventually to provide a set of general guidelines for AIE polymer design, along with personal perspectives on the direction of future research.
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Zhang, Huiqi. « Reprocessable Photodeformable Azobenzene Polymers ». Molecules 26, no 15 (23 juillet 2021) : 4455. http://dx.doi.org/10.3390/molecules26154455.
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Photodeformable azobenzene (azo) polymers are a class of smart polymers that can efficiently convert light energy into mechanical power, holding great promise in various photoactuating applications. They are typically of crosslinked polymer networks with highly oriented azo mesogens embedded inside. Upon exposure to the light of appropriate wavelength, they experience dramatic order parameter change following the configuration change of the azo units. This could result in the generation and accumulation of the gradient microscopic photomechanical force in the crosslinked polymer networks, thus leading to their macroscopic deformation. So far, a great number of photodeformable azo polymers have been developed, including some unoriented ones showing photodeformation based on different mechanisms. Among them, photodeformable azo polymers with dynamic crosslinking networks (and some uncrosslinked ones) have aroused particular interest recently because of their obvious advantages over those with stable chemical crosslinking structures such as high recyclability and reprocessability. In this paper, I provide a detailed overview of the recent progress in such reprocessable photodeformable polymers. In addition, some challenges and perspectives are also presented.
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Makino, Akira, et Shunsaku Kimura. « Solid Tumor-Targeting Theranostic Polymer Nanoparticle in Nuclear Medicinal Fields ». Scientific World Journal 2014 (2014) : 1–12. http://dx.doi.org/10.1155/2014/424513.
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Polymer nanoparticles can be prepared by self-assembling of amphiphilic polymers, and various types of molecular assemblies have been reported. In particular, in medicinal fields, utilization of these polymer nanoparticles as carriers for drug delivery system (DDS) has been actively tried, and some nanoparticulate drugs are currently under preclinical evaluations. A radionuclide is an unstable nucleus and decays with emission of radioactive rays, which can be utilized as a tracer in the diagnostic imaging systems of PET and SPECT and also in therapeutic purposes. Since polymer nanoparticles can encapsulate most of diagnostic and therapeutic agents with a proper design of amphiphilic polymers, they should be effective DDS carriers of radionuclides in the nuclear medicinal field. Indeed, nanoparticles have been recently attracting much attention as common platform carriers for diagnostic and therapeutic drugs and contribute to the development of nanotheranostics. In this paper, recent developments of solid tumor-targeting polymer nanoparticles in nuclear medicinal fields are reviewed.
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Kim, Junho, Eui Hyun Suh, Kyumin Lee, Gyuri Kim, Hansu Kim, Jaeyoung Jang et In Hwan Jung. « Development of Alkylthiazole-Based Novel Thermoelectric Conjugated Polymers for Facile Organic Doping ». Nanomaterials 13, no 7 (6 avril 2023) : 1286. http://dx.doi.org/10.3390/nano13071286.
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In this study, we developed two novel conjugated polymers that can easily be doped with F4TCNQ organic dopants using a sequential doping method and then studied their organic thermoelectric (OTE) properties. In particular, to promote the intermolecular ordering of OTE polymers in the presence of the F4TCNQ dopant, alkylthiazole-based conjugated building blocks with highly planar backbone structures were synthesized and copolymerized. All polymers showed strong molecular ordering and edge-on orientation in the film state, even in the presence of the F4TCNQ organic dopant. Thus, the sequential doping process barely changed the molecular ordering of the polymer films while making efficient molecular doping. In addition, the doping efficiency was improved in the more π-extended polymer backbones with thienothiophene units due to the emptier space in the polymer lamellar structure to locate ionized F4TCNQ. Moreover, the study of organic thin-film transistors (OTFTs) revealed that higher hole mobility in OTFTs was the key to increasing the electrical conductivity of OTE devices fabricated using the sequential doping method.
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Farahpour, Farnoush, Mohammad Reza Ejtehadi et Fathollah Varnik. « Polyelectrolytes polarization in nonuniform electric fields ». International Journal of Modern Physics C 25, no 12 (décembre 2014) : 1441010. http://dx.doi.org/10.1142/s0129183114410101.
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Stretching dynamics of polymers in microfluidics is of particular interest for polymer scientists. As a charged polymer, a polyelectrolyte (PE) can be deformed from its coiled equilibrium configuration to an extended chain by applying uniform or nonuniform electric fields. By means of hybrid lattice Boltzmann (LB)-molecular dynamics (MD) simulations, we investigate how the condensed counterions (CIs) around the PE contribute to the polymer stretching in inhomogeneous fields. As an application, we discuss the translocation phenomena and entropic traps, when the driving force is an applied external electric field.
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Fazi, Laura, Carla Andreani, Cadia D’Ottavi, Leonardo Duranti, Pietro Morales, Enrico Preziosi, Anna Prioriello et al. « Characterization of Conductive Carbon Nanotubes/Polymer Composites for Stretchable Sensors and Transducers ». Molecules 28, no 4 (13 février 2023) : 1764. http://dx.doi.org/10.3390/molecules28041764.
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The increasing interest in stretchable conductive composite materials, that can be versatile and suitable for wide-ranging application, has sparked a growing demand for studies of scalable fabrication techniques and specifically tailored geometries. Thanks to the combination of the conductivity and robustness of carbon nanotube (CNT) materials with the viscoelastic properties of polymer films, in particular their stretchability, “surface composites” made of a CNT on polymeric films are a promising way to obtain a low-cost, conductive, elastic, moldable, and patternable material. The use of polymers selected for specific applications, however, requires targeted studies to deeply understand the interface interactions between a CNT and the surface of such polymer films, and in particular the stability and durability of a CNT grafting onto the polymer itself. Here, we present an investigation of the interface properties for a selected group of polymer film substrates with different viscoelastic properties by means of a series of different and complementary experimental techniques. Specifically, we studied the interaction of a single-wall carbon nanotube (SWCNT) deposited on two couples of different polymeric substrates, each one chosen as representative of thermoplastic polymers (i.e., low-density polyethylene (LDPE) and polypropylene (PP)) and thermosetting elastomers (i.e., polyisoprene (PI) and polydimethylsiloxane (PDMS)), respectively. Our results demonstrate that the characteristics of the interface significantly differ for the two classes of polymers with a deeper penetration (up to about 100 μm) into the polymer bulk for the thermosetting substrates. Consequently, the resistance per unit length varies in different ranges, from 1–10 kΩ/cm for typical thermoplastic composite devices (30 μm thick and 2 mm wide) to 0.5–3 MΩ/cm for typical thermosetting elastomer devices (150 μm thick and 2 mm wide). For these reasons, the composites show the different mechanical and electrical responses, therefore suggesting different areas of application of the devices based on such materials.
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Barbosa, Hélder M. C., et Marta M. D. Ramos. « Computer Simulation of Hole Distribution in Polymeric Materials ». Materials Science Forum 587-588 (juin 2008) : 711–15. http://dx.doi.org/10.4028/www.scientific.net/msf.587-588.711.
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Polymers have been known for their flexibility and easy processing into coatings and films, which made them suitable to be applied in a variety of areas and in particular the growing area of organic electronics. The electronic properties of semiconducting polymers made them a serious rival in areas where until now inorganic materials were the most used, such as light emitting diodes or solar cells. Typical polymers can be seen as a network of molecular strands of varied lengths and orientations, with a random distribution of physical and chemical defects which makes them an anisotropic material. To further increase their performance, a better understanding of all aspects related to charge transport and space charge distribution in polymeric materials is required. The process associated with charge transport depends on the properties of the polymer molecules as well as connectivity and texture, and so we adopt a mesoscopic approach to build polymer structures. Changing the potential barrier for charge injection we can introduce holes in the polymer network and, by using a generalised Monte-Carlo method, we can simulate the transport of the injected charge through the polymer layer caused by imposing a voltage between two planar electrodes. Our results show that the way that holes distribute within polymer layer and charge localization in these materials is quite different from the inorganic ones.
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Palamarchuk, Aleksandr, Pavel Yudaev et Evgeniy Chistyakov. « Polymer Concretes Based on Various Resins : Modern Research and Modeling of Mechanical Properties ». Journal of Composites Science 8, no 12 (2 décembre 2024) : 503. https://doi.org/10.3390/jcs8120503.
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This review is devoted to experimental studies and modeling in the field of mechanical and physical properties of polymer concretes and polymer-modified concretes. The review analyzes studies carried out over the past two years. The paper examines the properties of polymer concretes based on various polymer resins and presents the advantages and disadvantages of various models developed to predict the mechanical properties of materials. Based on data in the literature, the most promising polymers for use in the field of road surface repair are polymer concretes with poly(meth)acrylic resins. It was found that the most adequate and productive models are the deep machine learning model—using several hidden layers that perform calculations based on input parameters—and the extreme gradient boosting model. In particular, the extreme gradient boosting model showed high R2 values in forecasting (in the range of 0.916–0.981) when predicting damping coefficient and ultimate compressive strength. In turn, among the additives to Portland cement concrete, the most promising are natural polymers, such as mammalian gelatin and cold fish gelatin, and superabsorbent polymers. These additives allow for an improvement in compressive strength of 200% or more. The review may be of interest to engineers specializing in building construction, materials scientists involved in the development and implementation of new materials into production, as well as researchers in the interdisciplinary fields of chemistry and technology.
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La Mantia, Francesco Paolo, Manuela Ceraulo, Maria Chiara Mistretta et Marco Morreale. « Effect of Cold Drawing on Mechanical Properties of Biodegradable Fibers ». Journal of Applied Biomaterials & ; Functional Materials 15, no 1 (26 janvier 2017) : 70–76. http://dx.doi.org/10.5301/jabfm.5000328.
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Purpose Biodegradable polymers are currently gaining importance in several fields, because they allow mitigation of the impact on the environment related to disposal of traditional, nonbiodegradable polymers, as well as reducing the utilization of oil-based sources (when they also come from renewable resources). Fibers made of biodegradable polymers are of particular interest, though, it is not easy to obtain polymer fibers with suitable mechanical properties and to tailor these to the specific application. The main ways to tailor the mechanical properties of a given biodegradable polymer fiber are based on crystallinity and orientation control. However, crystallinity can only marginally be modified during processing, while orientation can be controlled, either during hot drawing or cold stretching. In this paper, a systematic investigation of the influence of cold stretching on the mechanical and thermomechanical properties of fibers prepared from different biodegradable polymer systems was carried out. Methods Rheological and thermal characterization helped in interpreting the orientation mechanisms, also on the basis of the molecular structure of the polymer systems. Results and conclusions It was found that cold drawing strongly improved the elastic modulus, tensile strength and thermomechanical resistance of the fibers, in comparison with hot-spun fibers. The elastic modulus showed higher increment rates in the biodegradable systems upon increasing the draw ratio.