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1
Hili, Ryan, Chun Guo, Dehui Kong e Yi Lei. "Expanding the Chemical Diversity of DNA". Synlett 29, n. 11 (20 marzo 2018): 1405–14. http://dx.doi.org/10.1055/s-0036-1591959.
Testo completoAbstract (sommario):
Nucleic acid polymers can be evolved to exhibit desired properties, including molecular recognition of a molecular target and catalysis of a specific reaction. These properties can be readily evolved despite the dearth of chemical diversity available to nucleic acid polymers, especially when compared to the rich chemical complexity of proteins. Expansion of nucleic acid chemical diversity has therefore been an important thrust for improving their properties for analytical and biomedical applications. Herein, we briefly describe the current state-of-the-art for the sequence-defined incorporation of modifications throughout an evolvable nucleic acid polymer. This includes contributions from our own lab, which have expanded the chemical diversity of nucleic acid polymers closer to the level observed in proteinogenic polymers.1 Introduction2 Polymerase-Catalyzed Synthesis of Modified Nucleic Acid Polymers3 Ligase-Catalyzed Oligonucleotide Polymerization (LOOPER)4 LOOPER with Small Modifications5 LOOPER with Large Modifications6 Evolution of Aptamers Derived from LOOPER Libraries7 Outlook
2
Chen, Guang, Lei Tao e Ying Li. "Predicting Polymers’ Glass Transition Temperature by a Chemical Language Processing Model". Polymers 13, n. 11 (7 giugno 2021): 1898. http://dx.doi.org/10.3390/polym13111898.
Testo completoAbstract (sommario):
We propose a chemical language processing model to predict polymers’ glass transition temperature (Tg) through a polymer language (SMILES, Simplified Molecular Input Line Entry System) embedding and recurrent neural network. This model only receives the SMILES strings of a polymer’s repeat units as inputs and considers the SMILES strings as sequential data at the character level. Using this method, there is no need to calculate any additional molecular descriptors or fingerprints of polymers, and thereby, being very computationally efficient. More importantly, it avoids the difficulties to generate molecular descriptors for repeat units containing polymerization point ‘*’. Results show that the trained model demonstrates reasonable prediction performance on unseen polymer’s Tg. Besides, this model is further applied for high-throughput screening on an unlabeled polymer database to identify high-temperature polymers that are desired for applications in extreme environments. Our work demonstrates that the SMILES strings of polymer repeat units can be used as an effective feature representation to develop a chemical language processing model for predictions of polymer Tg. The framework of this model is general and can be used to construct structure–property relationships for other polymer properties.
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Brostow, Witold, Hanna Fałtynowicz, Osman Gencel, Andrei Grigoriev, Haley E. Hagg Lobland e Danny Zhang. "Mechanical and Tribological Properties of Polymers and Polymer-Based Composites". Chemistry & Chemical Technology 14, n. 4 (15 dicembre 2020): 514–20. http://dx.doi.org/10.23939/chcht14.04.514.
Testo completoAbstract (sommario):
A definition of rigidity of polymers and polymer-based composites (PBCs) by an equation is formulated. We also discuss tribological properties of polymers and PBCs including frictions (static, sliding and rolling) and wear. We discuss connections between viscoelastic recovery in scratch resistance testing with brittleness B, as well as Charpy and Izod impact strengths relations with B. Flexibility Y is related to a dynamic friction. A thermophysical property, namely linear thermal expansivity, is also related to the brittleness B. A discussion of equipment needed to measure a variety of properties is included.
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Chen, Jian Fang, e Ai Hua Ling. "Design and Synthesis of a Miktoarm Star PMMAZO-(PCL)2 Copolymer". Advanced Materials Research 332-334 (settembre 2011): 2089–92. http://dx.doi.org/10.4028/www.scientific.net/amr.332-334.2089.
Testo completoAbstract (sommario):
A series of novel miktoarm star polymers were synthesized by combination of at-om transfer radical polymerization(ATRP), chemical modification and ring-opening polymeri-zation(ROP). These miktoarm star polymers carring one poly[6-(4-methoxy-4’-oxy-azobenzene) hexylmethacrylate] azobenzene (PMMAZO) side-chain liquid crystalline(LC) arm and two polycaprolactone(PCL) arms. These precursors and miktoarm star polymers were characterized by proton nuclear resonance (1H-NMR), and gel permeation chramatograph(GPC). The information of PMMAZO(OH)2 and PMMAZO-(PCL)2 miktoarm star polymer confirmed the expected structure.
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Martens, C. M., R. Tuinier e M. Vis. "Depletion interaction mediated by semiflexible polymers". Journal of Chemical Physics 157, n. 15 (21 ottobre 2022): 154102. http://dx.doi.org/10.1063/5.0112015.
Testo completoAbstract (sommario):
We present a simple mean-field theory to describe the polymer-mediated depletion attraction between colloidal particles that accounts for the polymer’s chain stiffness. We find that for fixed polymer radius of gyration and volume fraction, the strength of this attraction increases with increasing chain stiffness in both dilute and semidilute concentration regimes. In contrast, the range of attraction monotonically decreases with chain stiffness in the dilute regime, while it attains a maximum in the semidilute regime. The obtained analytical expressions for the depletion interaction were compared with numerical self-consistent field lattice computations and shown to be in quantitative agreement. From the interaction potential between two spheres, we calculated the second osmotic virial coefficient B2, which appears to be a convex function of chain stiffness. A minimum of B2 as a function of chain stiffness was observed both in the numerical self-consistent field computations and the analytical theory. These findings help explain the general observation that semiflexible polymers are more effective depletants than flexible polymers and give insight into the phase behavior of mixtures containing spherical colloids and semiflexible polymers.
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Shahzadi, Maria, Taimoor Hassan e Sana Saeed. "Application of Natural Polymers in Wound Dressings". Pakistan Journal of Medical and Health Sciences 16, n. 10 (30 ottobre 2022): 1–2. http://dx.doi.org/10.53350/pjmhs2216101.
Testo completoAbstract (sommario):
Natural polymers because of their biodegradability, biocompatibility and closeness to the extracellular matrix are frequently used in regenerative medicine for burns and wound dressing. By triggering and stimulating the wound healing process, natural polymers aid in the restoration of damaged tissues and, as a result, skin regeneration1. Natural polymers have proven to be effective in a variety of biomedical applications, such as controlled administration of drugs, gene delivery, and regenerative medicine, among others.Plants, animals, and microbial are the major sources responsible for production of natural polymers. Based on their chemistry natural polymers are divided into polysaccharide, protein, polyester, and polyamide-based polymers2. Because of their 3 D cross-link-based networks of polymer, immersed with water or other biological fluids, hydrogels are considered worthwhile in the Biomedical and pharmaceutical industries for wound care, burn dressing, medication administration, tissue engineering and transplantation of organs3. Natural polymers used in wound dressings: Here are several natural polymers which are effectively used in wound management.
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Caldona, Eugene B., Ernesto I. Borrego, Ketki E. Shelar, Karl M. Mukeba e Dennis W. Smith. "Ring-Forming Polymerization toward Perfluorocyclobutyl and Ortho-Diynylarene-Derived Materials: From Synthesis to Practical Applications". Materials 14, n. 6 (18 marzo 2021): 1486. http://dx.doi.org/10.3390/ma14061486.
Testo completoAbstract (sommario):
Many desirable characteristics of polymers arise from the method of polymerization and structural features of their repeat units, which typically are responsible for the polymer’s performance at the cost of processability. While linear alternatives are popular, polymers composed of cyclic repeat units across their backbones have generally been shown to exhibit higher optical transparency, lower water absorption, and higher glass transition temperatures. These specifically include polymers built with either substituted alicyclic structures or aromatic rings, or both. In this review article, we highlight two useful ring-forming polymer groups, perfluorocyclobutyl (PFCB) aryl ether polymers and ortho-diynylarene- (ODA) based thermosets, both demonstrating outstanding thermal stability, chemical resistance, mechanical integrity, and improved processability. Different synthetic routes (with emphasis on ring-forming polymerization) and properties for these polymers are discussed, followed by their relevant applications in a wide range of aspects.
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Ewert, Ernest, Izabela Pospieszna-Markiewicz, Martyna Szymańska, Adrianna Kurkiewicz, Agnieszka Belter, Maciej Kubicki, Violetta Patroniak, Marta A. Fik-Jaskółka e Giovanni N. Roviello. "New N4-Donor Ligands as Supramolecular Guests for DNA and RNA: Synthesis, Structural Characterization, In Silico, Spectrophotometric and Antimicrobial Studies". Molecules 28, n. 1 (3 gennaio 2023): 400. http://dx.doi.org/10.3390/molecules28010400.
Testo completoAbstract (sommario):
The present work reports the synthesis of new N4-donor compounds carrying p-xylyl spacers in their structure. Different Schiff base aliphatic N-donors were obtained synthetically and subsequently evaluated for their ability to interact with two models of nucleic acids: calf-thymus DNA (CT-DNA) and the RNA from yeast Saccharomyces cerevisiae (herein simply indicated as RNA). In more detail, by condensing p-xylylenediamine and a series of aldehydes, we obtained the following Schiff base ligands: 2-thiazolecarboxaldehyde (L1), pyridine-2-carboxaldehyde (L2), 5-methylisoxazole-3-carboxaldehyde (L3), 1-methyl-2-imidazolecarboxaldehyde (L4), and quinoline-2-carboxaldehyde (L5). The structural characterisation of the ligands L1-L5 (X-ray, 1H NMR, 13C NMR, elemental analysis) and of the coordination polymers {[CuL1]PF6}n (herein referred to as Polymer1) and {[AgL1]BF4}n, (herein referred to as Polymer2, X-ray, 1H NMR, ESI-MS) is herein described in detail. The single crystal X-ray structures of complexes Polymer1 and Polymer2 were also investigated, leading to the description of one-dimensional coordination polymers. The spectroscopic and in silico evaluation of the most promising compounds as DNA and RNA binders, as well as the study of the influence of the 1D supramolecular polymers Polymer1 and Polymer2 on the proliferation of Escherichia coli bacteria, were performed in view of their nucleic acid-modulating and antimicrobial applications. Spectroscopic measurements (UV–Vis) combined with molecular docking calculations suggest that the thiazolecarboxaldehyde derivative L1 is able to bind CT-DNA with a mechanism different from intercalation involving the thiazole ring in the molecular recognition and shows a binding affinity with DNA higher than RNA. Finally, Polymer2 was shown to slow down the proliferation of bacteria much more effectively than the free Ag(I) salt.
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Becskereki, Gergely, George Horvai e Blanka Tóth. "The Selectivity of Molecularly Imprinted Polymers". Polymers 13, n. 11 (28 maggio 2021): 1781. http://dx.doi.org/10.3390/polym13111781.
Testo completoAbstract (sommario):
The general claim about novel molecularly imprinted polymers is that they are selective for their template or for another target compound. This claim is usually proved by some kind of experiment, in which a performance parameter of the imprinted polymer is shown to be better towards its template than towards interferents. A closer look at such experiments shows, however, that different experiments may differ substantially in what they tell about the same imprinted polymer’s selectivity. Following a short general discussion of selectivity concepts, the selectivity of imprinted polymers is analyzed in batch adsorption, binding assays, chromatography, solid phase extraction, sensors, membranes, and catalysts. A number of examples show the problems arising with each type of application. Suggestions for practical method design are provided.
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Chang, L. L., D. L. Raudenbush e S. K. Dentel. "Aerobic and anaerobic biodegradability of a flocculant polymer". Water Science and Technology 44, n. 2-3 (1 luglio 2001): 461–68. http://dx.doi.org/10.2166/wst.2001.0802.
Testo completoAbstract (sommario):
Flocculant polymers are used to improve the efficiency of separation processes used in wastewater treatment. The subsequent fate and effects of these additives are uncertain, however, with some previous reports indicating them to be biodegradable while others indicate complete recalcitrance. The biodegradability of a common flocculant polymer was therefore evaluated, using both aerobic and anaerobic batch assays. Knowledge of the polymer's chemical composition also allowed degradation stoichiometries to be calculated for complete biodegradation and also for incomplete degradation to several hypothesized end products. Results showed conclusively that the polymer was subject to partial degradation by both aerobic and anaerobic cultures. Measured oxygen consumption under aerobic conditions, and gas production under anaerobic conditions, both indicate that the partial destruction of pendant cationic moieties occurs, but that the polymer's CH2 backbone remains essentially intact. These results allow seemingly contradictory previous reports to be explained. The findings are relevant to the environmental fate of these polymers as well as certain treatment process effects.
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Gabler, Anna Maria, Annalena Ludwig, Florian Biener, Magdalena Waldner, Corinna Dawid e Oliver Frank. "Chemical Characterization of Red Wine Polymers and Their Interaction Affinity with Odorants". Foods 13, n. 4 (8 febbraio 2024): 526. http://dx.doi.org/10.3390/foods13040526.
Testo completoAbstract (sommario):
In order to characterize red wine polymers with regard to their binding properties to aroma compounds (odorants), a qualitative and quantitative analysis of chemical degradation products after different chemical treatments (thiolytic, acidic, and alkaline depolymerization) of high -molecular-weight (HMW) fractions of red wine was performed. Using 1H NMR, LC-ToF-MS, LCMS/MS, and HPIC revealed key structural features such as carbohydrates, organic acids, phenolic compounds, anthocyanins, anthocyanidins, amino acids, and flavan-3-ols responsible for odorant-polymer interactions. Further, NMR-based interaction studies of the selected aroma compounds 3methylbutanol, cis-whisky lactone, 3-methylbutanoic acid, and 3-isobutyl-2-methoxypyrazine with HMW polymers after chemical treatment demonstrated a reduced interaction affinity of the polymer compared to the native HMW fractions, and further, the importance of aromatic compounds such as flavan-3-ols for the formation of odorant polymer interactions. In addition, these observations could be verified by human sensory experiments. For the first time, the combination of a compositional analysis of red wine polymers and NMR-based interaction studies with chemically treated HMW fractions enabled the direct analysis of the correlation of the polymer’s structure and its interaction affinity with key odorants in red wine.
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Quintero Perez, Henderson Ivan, Maria Carolina Ruiz Cañas, Ruben Hernan Castro Garcia e Arnold Rafael Romero Bohorquez. "Use of nanoparticles to improve thermochemical resistance of synthetic polymer to enhanced oil recovery applications: a review". CT&F - Ciencia, Tecnología y Futuro 10, n. 2 (17 dicembre 2020): 85–97. http://dx.doi.org/10.29047/01225383.259.
Testo completoAbstract (sommario):
Partially Hydrolyzed Polyacrylamide (HPAM) is the polymer most used in chemical enhanced oil recovery (cEOR) processes and it has been implemented in several field projects worldwide. Polymer injection has shown to be an effective EOR process. However, it has not been implemented massively due to HPAM polymer's limitations, mostly related to thermal and chemical degradation caused by exposure at high temperatures and salinities (HTHS). As an alternative, a new generation of chemically stable monomers to improve the properties of HPAM has been assessed at laboratory and field conditions. However, the use of enhanced polymers is limited due to its larger molecular size, large-scale production, and higher costs.
One of the alternatives proposed in the last decade to improve polymer properties is the use of nanoparticles, which due to their ultra-small size, large surface area, and highly reactive capacity, can contribute to reduce or avoid the degrading processes of HPAM polymers. Nanoparticles (NPs) can be integrated with the polymer in several ways, it being worth to highlight mixing with the polymer in aqueous solution or inclusion by grafting or chemical functionalization on the nanoparticle surface. This review focuses on hybrid nanomaterials based on SiO2 NPs and synthetic polymers with great EOR potential. The synthesis process, characterization, and the main properties for application in EOR processes, were reviewed and analyzed.
Nanohybrids based on polymers and silica nanoparticles show promising results in improving viscosity and thermal stability compared to the HPAM polymer precursor. Furthermore, based on recent findings, there are great opportunities to implement polymer nanofluids in cEOR projects. This approach could be of value to optimize the technical-economic feasibility of projects by reducing the polymer concentration of using reasonable amounts of nanoparticles. However, more significant efforts are required to understand the impact of nanoparticle concentrations and injection rates to support the upscaling of this cEOR technology.
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Chitrakar, Chandani, Marc Anthony Torres, Pedro Emanuel Rocha-Flores, Qichan Hu e Melanie Ecker. "Multifaceted Shape Memory Polymer Technology for Biomedical Application: Combining Self-Softening and Stretchability Properties". Polymers 15, n. 21 (25 ottobre 2023): 4226. http://dx.doi.org/10.3390/polym15214226.
Testo completoAbstract (sommario):
Thiol-ene polymers are a promising class of biomaterials with a wide range of potential applications, including organs-on-a-chip, microfluidics, drug delivery, and wound healing. These polymers offer flexibility, softening, and shape memory properties. However, they often lack the inherent stretchability required for wearable or implantable devices. This study investigated the incorporation of di-acrylate chain extenders to improve the stretchability and conformability of those flexible thiol-ene polymers. Thiol-ene/acrylate polymers were synthesized using 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATATO), Trimethylolpropanetris (3-mercaptopropionate) (TMTMP), and Polyethylene Glycol Diacrylate (PEGDA) with different molecular weights (Mn 250 and Mn 575). Fourier Transform Infrared (FTIR) spectroscopy confirmed the complete reaction among the monomers. Uniaxial tensile testing demonstrated the softening and stretching capability of the polymers. The Young’s Modulus dropped from 1.12 GPa to 260 MPa upon adding 5 wt% PEGDA 575, indicating that the polymer softened. The Young’s Modulus was further reduced to 15 MPa under physiologic conditions. The fracture strain, a measure of stretchability, increased from 55% to 92% with the addition of 5 wt% PEGDA 575. A thermomechanical analysis further confirmed that PEGDA could be used to tune the polymer’s glass transition temperature (Tg). Moreover, our polymer exhibited shape memory properties. Our results suggested that thiol-ene/acrylate polymers are a promising new class of materials for biomedical applications requiring flexibility, stretchability, and shape memory properties.
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Kerr-Phillips, Thomas, Mona Damavandi, Lisa I. Pilkington, Kathryn A. Whitehead, Jadranka Travas-Sejdic e David Barker. "Effects of Neutral, Anionic and Cationic Polymer Brushes Grafted from Poly(para-phenylene vinylene) and Poly(para-phenylene ethynylene) on the Polymer’s Photoluminescent Properties". Polymers 14, n. 14 (6 luglio 2022): 2767. http://dx.doi.org/10.3390/polym14142767.
Testo completoAbstract (sommario):
The conformation of a fluorescent polymer, in the solid state or in solution, plays a critical role in the polymer’s fluorescent properties. Thus, grafted side chains on a fluorescent polymer can directly influence its optical properties. In this study, the effect of grafted polymeric side chains on the photoluminescent properties of poly(para-phenylene vinylene) (PPV) and poly(para-phenylene ethynylene) (PPE) were investigated. Low- and high-molecular-weight grafts of neutral poly(n-butyl acrylate), cationic poly(trimethylaminoethyl methacrylate) and anionic poly(sulfopropyl acrylate) were grafted onto PPVs and PPEs, and the effect of the grafting on the graft copolymer’s absorption and emission wavelengths, the fluorescence intensity and the quantum yield were studied. The results indicate that in the case of the ionic grafts, contrary to the expectations, the polymers have a reduced quantum yield. This contrasts with the copolymers with uncharged side chains (PnBA), where a major increase in the quantum yield is seen for the self-quenching conjugated pristine polymers. These results reinforce that the molecular conformation of the polymer in a solid or solution plays a critical role in fluorescent polymers photoluminescent properties.
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Kumar, Vipin. "Microcellular Polymers: Novel Materials for the 21st Century". Cellular Polymers 12, n. 3 (maggio 1993): 207–23. http://dx.doi.org/10.1177/026248939301200303.
Testo completoAbstract (sommario):
Microcellular polymer's produced by gas nucleation, refer to closed cell thermoplastic foams with a very large number of very small cells—typically 108 or more cells per cm3 of order 10μm in diameter. First produced in the early 1980's with the objective of reducing the amount of polymer used in mass produced items, these novel materials have the potential to revolutionize the way thermoplastic polymers are used today. Microcellular plastics have been produced from a number of polymers ranging in relative density from 0.1 to 1.0, containing 108 to 1011 cells per cm3, offering the engineer a new range of properties for design. The microcellular polymers appear to possess improved fatigue life and energy absorption characteristics as well as a higher specific strength. This paper reviews recent progress in this emerging technology and discusses the areas where this technology is likely to make an impact in the future.
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Elacqua, Elizabeth, Stephen J. Koehler e Jinzhen Hu. "Electronically Governed ROMP: Expanding Sequence Control for Donor–Acceptor Conjugated Polymers". Synlett 31, n. 15 (14 luglio 2020): 1435–42. http://dx.doi.org/10.1055/s-0040-1707180.
Testo completoAbstract (sommario):
Controlling the primary sequence of synthetic polymers remains a grand challenge in chemistry. A variety of methods that exert control over monomer sequence have been realized wherein differential reactivity, pre-organization, and stimuli-response have been key factors in programming sequence. Whereas much has been established in nonconjugated systems, π-extended frameworks remain systems wherein subtle structural changes influence bulk properties. The recent introduction of electronically biased ring-opening metathesis polymerization (ROMP) extends the repertoire of feasible approaches to prescribe donor–acceptor sequences in conjugated polymers, by enabling a system to achieve both low dispersity and controlled polymer sequences. Herein, we discuss recent advances in obtaining well-defined (i.e., low dispersity) polymers featuring donor–acceptor sequence control, and present our design of an electronically ambiguous (4-methoxy-1-(2-ethylhexyloxy) and benzothiadiazole-(donor–acceptor-)based [2.2]paracyclophanediene monomer that undergoes electronically dictated ROMP. The resultant donor–acceptor polymers were well-defined (Đ = 1.2, Mn > 20 k) and exhibited lower energy excitation and emission in comparison to ‘sequence-ill-defined’ polymers. Electronically driven ROMP expands on prior synthetic methods to attain sequence control, while providing a promising platform for further interrogation of polymer sequence and resultant properties.1 Introduction to Sequence Control2 Sequence Control in Polymers3 Multistep-Synthesis-Driven Sequence Control4 Catalyst-Dictated Sequence Control5 Electronically Governed Sequence Control6 Conclusions
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La Mesa, Camillo. "Hybrid Colloids Made with Polymers". Applied Sciences 14, n. 12 (13 giugno 2024): 5135. http://dx.doi.org/10.3390/app14125135.
Testo completoAbstract (sommario):
Polymers adsorb onto nanoparticles, NPs, by different mechanisms. Thus, they reduce coagulation, avoid undesired phase separation or clustering, and give rise to hybrid colloids. These find uses in many applications. In cases of noncovalent interactions, polymers adsorb onto nanoparticles, which protrude from their surface; the polymer in excess remains in the medium. In covalent mode, conversely, polymers form permanent links with functional groups facing outward from the NPs’ surface. Polymers in contact with the solvent minimize attractive interactions among the NPs. Many contributions stabilize such adducts: the NP–polymer, polymer–polymer, and polymer–solvent interaction modes are the most relevant. Changes in the degrees of freedom of surface-bound polymer portions control the stability of the adducts they form with NPs. Wrapped, free, and protruding polymer parts favor depletion and control the adducts’ properties if surface adsorption is undesired. The binding of surfactants onto NPs takes place too, but their stabilizing effect is much less effective than the one due to polymers. The underlying reason for this is that surfactants easily adsorb onto surfaces, but they desorb if the resulting adducts are not properly stabilized. Polymers interact with surfactants, both when the latter are in molecular or associated forms. The interactions occur between polymers and ionic surfactants or amphiphiles associated with vesicular entities. Hybrids obtained in these ways differ each from each other. The mechanisms governing hybrid formation are manifold and span from being purely electrostatic to other modes. The adducts that do form are quite diverse in their sizes, shapes, and features, and depend significantly on composition and mole ratios. Simple approaches clarify the interactions among different particle types that yield hybrids.
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Lavine, M. S. "POLYMER CHEMISTRY: Arborescent Polymers". Science 294, n. 5540 (5 ottobre 2001): 15d—15. http://dx.doi.org/10.1126/science.294.5540.15d.
Testo completo
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Jablonský, Michal, Andrea Škulcová e Jozef Šima. "Use of Deep Eutectic Solvents in Polymer Chemistry–A Review". Molecules 24, n. 21 (3 novembre 2019): 3978. http://dx.doi.org/10.3390/molecules24213978.
Testo completoAbstract (sommario):
This review deals with two overlapping issues, namely polymer chemistry and deep eutectic solvents (DESs). With regard to polymers, specific aspects of synthetic polymers, polymerization processes producing such polymers, and natural cellulose-based nanopolymers are evaluated. As for DESs, their compliance with green chemistry requirements, their basic properties and involvement in polymer chemistry are discussed. In addition to reviewing the state-of-the-art for selected kinds of polymers, the paper reveals further possibilities in the employment of DESs in polymer chemistry. As an example, the significance of DES polarity and polymer polarity to control polymerization processes, modify polymer properties, and synthesize polymers with a specific structure and behavior, is emphasized.
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Briscoe, B. J., e S. K. Sinha. "Wear of polymers". Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 216, n. 6 (1 giugno 2002): 401–13. http://dx.doi.org/10.1243/135065002762355325.
Testo completoAbstract (sommario):
This paper reviews some of the recent progress which has been made in the area of the sliding wear of polymers. Wear mechanisms are classified under three broad approaches which reflect primarily the way this subject has been historically studied. It is demonstrated here that the wear of polymers is influenced by the contact conditions, the bulk mechanical properties of the polymer and the properties of the ‘third body’, which generally appears in the form of transfer film or degraded polymer particles between two sliding surfaces. Further, this paper establishes a link between the different contact and material parameters and shows how they are important in elucidating the generic wear mechanisms for polymers. The effects of environment and lubrication upon polymer wear are briefly explained in terms of the chemical interactions between the liquid phase and the polymer. The capabilities and limitations of current predictive wear models for polymeric contacts are also highlighted.
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Yu, Xiaomei, Ting Li, Lin Hao e Dacheng Zhang. "PCR Microchip Array Based on Polymer Bonding Technique". Journal of Electronic Packaging 127, n. 1 (1 marzo 2005): 38–42. http://dx.doi.org/10.1115/1.1849231.
Testo completoAbstract (sommario):
A polymerase chain reaction (PCR) microchip array with a dimension of 21.3×17.5 mm2 has been fabricated by the silicon micromachining technique. The chip is composed of 192 rectangular reaction chambers with the volume of 50 nL. In order to package the silicon-based PCR chip, a low-temperature bonding technique using polymers as the intermediate layers has been developed. The tested polymers include positive photoresist, polyimide, and epoxy. Using stamping and sandwich techniques, void-free and liquid-proof bondings of silicon to a glass cover were achieved with the three polymers. The experimental results of fluorescence-based PCR demonstrate that the DNA amplification can be performed in the chip arrays with nanoliter volumes and the polymer bonding technique is biocompatible and suitable for the microchip packaging.
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De Cachinho Cordeiro, Ivan Miguel, Ao Li, Bo Lin, Daphne Xiuyun Ma, Lulu Xu, Alice Lee-Sie Eh e Wei Wang. "Solid Polymer Electrolytes for Zinc-Ion Batteries". Batteries 9, n. 7 (27 giugno 2023): 343. http://dx.doi.org/10.3390/batteries9070343.
Testo completoAbstract (sommario):
To date, zinc-ion batteries (ZIBs) have been attracting extensive attention due to their outstanding properties and the potential to be the solution for next-generation energy storage systems. However, the uncontrollable growth of zinc dendrites and water-splitting issues seriously restrict their further scalable application. Over the past few years, solid polymer electrolytes (SPEs) have been regarded as a promising alternative to address these challenges and facilitate the practical advancement of zinc batteries. In this review, we revisit the research progress of SPEs applied in zinc batteries in the past few years and focus on introducing cutting-edge polymer science and technologies that can be utilised to prepare advanced SPEs for high-performance zinc batteries. The operating mechanism of SPEs and the functions of polymers are summarised. To highlight the polymer’s functions, SPEs are categorised into three types, homogenous polymer SPEs, hybrids polymer SPEs, and nanocomposites SPEs, which are expected to reveal the roles and principles of various polymers in zinc batteries. This review presents the current research progress and fundamental mechanisms of polymer-based SPEs in zinc batteries, outlines the challenging issues encountered, and proposes potential solutions for future endeavours.
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Tehrani, Pezhman Soltani, Hamzeh Ghorbani, Sahar Lajmorak, Omid Molaei, Ahmed E. Radwan e Saeed Parvizi Ghaleh. "Laboratory study of polymer injection into heavy oil unconventional reservoirs to enhance oil recovery and determination of optimal injection concentration". AIMS Geosciences 8, n. 4 (2022): 579–92. http://dx.doi.org/10.3934/geosci.2022031.
Testo completoAbstract (sommario):
<abstract> <p>Polymers have been used for many years to control the mobility of injected water and increase the rate of oil extraction from unconventional reservoirs. Polymer flossing improves the volume of the broom, reduces the finger effect, creates channels, and delays water breakage. The combination of these processes has the potential to increase oil production and reduce production costs. To carry out this process, various polymers are used alone or in combination with surfactants and alkalis. In this study, a new type of polymer called FLOPPAM 3630 has been used to investigate the overload of very heavy oil reservoirs. For this purpose, six polymer solutions with different concentrations were made, and stability tests on shear rate, time, and temperature were performed. The polymer's stability results indicate that it is stable under other shear rate, temperature, and time passage conditions. As a result, this polymer is a suitable candidate for conducting silicification tests in reservoir temperature conditions. Then three more suitable polymer solutions were selected, and the polymer was polished. The results showed that the solution with a concentration of 1000 ppm has the best yield of about 40%. The reason for the good efficiency of this concentration is that the surface and vertical sweepers are higher than the other concentrations. Also, the difference in efficiency between less than 1000 and 2000 ppm is greater because it is more economical, and its injectability is easier to use with less concentration. Furthermore, the oil efficiency of this type of polymer in sandblasting is higher than that of other polymers tested under these conditions, making its use more economical.</p> </abstract>
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Kozhevnikov, Н. V., N. I. Kozhevnikova e M. D. Goldfeyn. "Solving Some Environmental Problems of Polymer Chemistry". Izvestiya of Saratov University. Chemistry. Biology. Ecology 10, n. 2 (2010): 34–42. http://dx.doi.org/10.18500/1816-9775-2010-10-2-34-42.
Testo completoAbstract (sommario):
The kinetics and mechanism of vinyl monomer polymerization were studied. Ways to solve some environmental problems of polymer chemistry have been developed, namely, monomer stabilization to avoid the formation of side polymers due to spontaneous polymeriza tion while synthesis, purification and storage of monomers, synthesis of environmentally-pure emulgator-free latexes, synthesis of polymer ic flocculants for water purification from disperse particles.
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Tyagi, Upendra N., e Paul T. Bowen. "Polymer Characteristics and Attachment Sites in the Sludge Matrix". Water Science and Technology 21, n. 8-9 (1 agosto 1989): 899–908. http://dx.doi.org/10.2166/wst.1989.0292.
Testo completoAbstract (sommario):
This study identified polymer attachment sites in three types of sludge for different molecular weight and charge density cationic polymers. Conditioned and unconditioned sludge samples were treated with cationized ferritin (CF) to label anionic charged sites on the surface of sludge particles. Sludge surfaces were examined using transmission electron microscopy. The presence of CF indicates an anionic site not attached to polymers. For increasing polymer molecular weight, comparison of micrographs of samples conditioned with similar polymer doses showed an increase in CF attachment. Therefore polymer attachment was seen to decrease with increasing polymer molecular weight. At extremely high polymer dosages, the presence of CF indicates that anionic sites have not been saturated by polymers. These results imply the molecular weight (chain length) and structure of polymers may determine the mechanisms of polymer action. No appreciable differences were observed for sludges conditioned with polymers of various charge densities.
26
Fuller, Carl W., Shiv Kumar, Mintu Porel, Minchen Chien, Arek Bibillo, P. Benjamin Stranges, Michael Dorwart et al. "Real-time single-molecule electronic DNA sequencing by synthesis using polymer-tagged nucleotides on a nanopore array". Proceedings of the National Academy of Sciences 113, n. 19 (18 aprile 2016): 5233–38. http://dx.doi.org/10.1073/pnas.1601782113.
Testo completoAbstract (sommario):
DNA sequencing by synthesis (SBS) offers a robust platform to decipher nucleic acid sequences. Recently, we reported a single-molecule nanopore-based SBS strategy that accurately distinguishes four bases by electronically detecting and differentiating four different polymer tags attached to the 5′-phosphate of the nucleotides during their incorporation into a growing DNA strand catalyzed by DNA polymerase. Further developing this approach, we report here the use of nucleotides tagged at the terminal phosphate with oligonucleotide-based polymers to perform nanopore SBS on an α-hemolysin nanopore array platform. We designed and synthesized several polymer-tagged nucleotides using tags that produce different electrical current blockade levels and verified they are active substrates for DNA polymerase. A highly processive DNA polymerase was conjugated to the nanopore, and the conjugates were complexed with primer/template DNA and inserted into lipid bilayers over individually addressable electrodes of the nanopore chip. When an incoming complementary-tagged nucleotide forms a tight ternary complex with the primer/template and polymerase, the tag enters the pore, and the current blockade level is measured. The levels displayed by the four nucleotides tagged with four different polymers captured in the nanopore in such ternary complexes were clearly distinguishable and sequence-specific, enabling continuous sequence determination during the polymerase reaction. Thus, real-time single-molecule electronic DNA sequencing data with single-base resolution were obtained. The use of these polymer-tagged nucleotides, combined with polymerase tethering to nanopores and multiplexed nanopore sensors, should lead to new high-throughput sequencing methods.
27
Sun, Linghui, Zhirong Zhang, Kaiqi Leng, Bowen Li, Chun Feng e Xu Huo. "Can Supramolecular Polymers Become Another Material Choice for Polymer Flooding to Enhance Oil Recovery?" Polymers 14, n. 20 (18 ottobre 2022): 4405. http://dx.doi.org/10.3390/polym14204405.
Testo completoAbstract (sommario):
High molecular polymers have been widely studied and applied in the field of enhanced oil recovery (EOR). At present, the focus of research has been changed to the design of polymer networks with unique properties such as anti-temperature and anti-salinity, good injection and so on. Supramolecular polymers have high viscoelasticity as well as excellent temperature, salt resistance and injection properties. Can supramolecular polymers become another material choice for polymer flooding to enhance oil recovery? The present review aims to systematically introduce supramolecular polymers, including its design strategy, interactions and rheological properties, and address three main concerns: (1) Why choose supramolecular polymers? (2) How do we synthesize and characterize supramolecular polymers in the field of oilfield chemistry? (3) What has been the application progress of supramolecular polymers in improving oil recovery? The introduction of a supramolecular interaction system provides a new idea for polymer flooding and opens up a new research direction to improve oil recovery. Aiming at the “reversible dynamic” supramolecular polymers, the supramolecular polymers are compared with the conventional covalent macromolecular polymer networks, and the challenges and future research directions of supramolecular polymers in EOR are discussed. Finally, the author’s viewpoints and perspectives in this emerging field are discussed.
28
Hu, Wenping, Hiroshi Nakashima, Erjing Wang, Kazuaki Furukawa, Hongxiang Li, Yi Luo, Zhigang Shuai, Yoshiaki Kashimura, Yunqi Liu e Keiichi Torimitsu. "Advancing conjugated polymers into nanometer-scale devices". Pure and Applied Chemistry 78, n. 10 (1 gennaio 2006): 1803–22. http://dx.doi.org/10.1351/pac200678101803.
Testo completoAbstract (sommario):
In this article, we review the possibility of combining conjugated polymers with nanometer-scale devices (nanodevices), in order to introduce the properties associated with conjugated polymers into such nanodevices. This approach envisages combining the highly topical disciplines of polymer electronics and nanoelectronics to engender a new subdirection of polymer nanoelectronics, which can serve as a tool to probe the behavior of polymer molecules at the nanometer/molecular level, and contribute to clarifying transport mechanisms in conjugated polymers. In this study, we exemplify this combination, using a family of linear and conjugated polymers, poly(p-phenylene-ethynylene)s (PPEs) with thiolacetate-functionalized end groups.
29
Lutz, Jean-François, Makoto Ouchi, David R. Liu e Mitsuo Sawamoto. "Sequence-Controlled Polymers". Science 341, n. 6146 (8 agosto 2013): 1238149. http://dx.doi.org/10.1126/science.1238149.
Testo completoAbstract (sommario):
Sequence-controlled polymers are macromolecules in which monomer units of different chemical nature are arranged in an ordered fashion. The most prominent examples are biological and have been studied and used primarily by molecular biologists and biochemists. However, recent progress in protein- and DNA-based nanotechnologies has shown the relevance of sequence-controlled polymers to nonbiological applications, including data storage, nanoelectronics, and catalysis. In addition, synthetic polymer chemistry has provided interesting routes for preparing nonnatural sequence-controlled polymers. Although these synthetic macromolecules do not yet compare in functional scope with their natural counterparts, they open up opportunities for controlling the structure, self-assembly, and macroscopic properties of polymer materials.
30
Parnian, Pooyan, e Alberto D’Amore. "Fabrication of High-Performance CNT Reinforced Polymer Composite for Additive Manufacturing by Phase Inversion Technique". Polymers 13, n. 22 (19 novembre 2021): 4007. http://dx.doi.org/10.3390/polym13224007.
Testo completoAbstract (sommario):
Additive Manufacturing (AM) of polymer composites has enabled the fabrication of highly customized parts with notably mechanical properties, thermal and electrical conductivity compared to un-reinforced polymers. Employing the reinforcements was a key factor in improving the properties of polymers after being 3D printed. However, almost all the existing 3D printing methods could make the most of disparate fiber reinforcement techniques, the fused filament fabrication (FFF) method is reviewed in this study to better understand its flexibility to employ for the proposed novel method. Carbon nanotubes (CNTs) as a desirable reinforcement have a great potential to improve the mechanical, thermal, and electrical properties of 3D printed polymers. Several functionalization approaches for the preparation of CNT reinforced composites are discussed in this study. However, due to the non-uniform distribution and direction of reinforcements, the properties of the resulted specimen do not change as theoretically expected. Based on the phase inversion method, this paper proposes a novel technique to produce CNT-reinforced filaments to simultaneously increase the mechanical, thermal, and electrical properties. A homogeneous CNT dispersion in a dilute polymer solution is first obtained by sonication techniques. Then, the CNT/polymer filaments with the desired CNT content can be obtained by extracting the polymer’s solvent. Furthermore, optimizing the filament draw ratio can result in a reasonable CNT orientation along the filament stretching direction.
31
Ainurofi, Ahmad, Amalia Daryati, Faradisania A. Murtadla, Fatimatus Salimah, Nila M. Akbar e Rizka A. Faizun. "The Use of Natural and Synthetic Polymers in the Formulation of Gastro retentive Drug Delivery System". INTERNATIONAL JOURNAL OF DRUG DELIVERY TECHNOLOGY 13, n. 01 (25 marzo 2023): 434–41. http://dx.doi.org/10.25258/ijddt.13.1.69.
Testo completoAbstract (sommario):
The gastric emptying process drastically reduces the bioavailability of drugs that target the stomach for their action. A gastro retentive drug delivery system (GRDDS) becomes a solution to retain drugs in the stomach and release drugs from the formulation system within a certain period. The polymer used in the GRDDS formulation is the essential excipient that can retain the drugs in the stomach. Several ways for GRDDS to maintain its existence in the stomach are using some systems, such as mucoadhesive, low-density, high-density, swellable, eff ervescent, and expandable systems. A polymer is a macromolecular substance with a long repeating chain consisting of natural and synthetic polymers, each with diff erent potentials. It is considered for its ability to regulate drug release, good fl ow properties, can improve drug dissolution to improve bioavailability and stability during processing in the body. Combining natural and synthetic polymers is often carried out to obtain advantages and cover the existing polymer’s disadvantages. Polymers can release drugs using three diff erent mechanisms, i.e., diff usion, degradation, and expansion. These techniques are often chosen for the formulation of GRDDS because of their more fl exible system and fi t for almost all types of GRDDS. The polymer used in the GRDDS system is chosen from its physicochemical properties and the number of fl oating times, drug release rate, viscosity, fl oating lag times, bioavailability, and solubility.
32
Kumar, Naveen, Sonia Pahuja e Ranjit Sharma. "Pharmaceutical Polymers - A Review". International Journal of Drug Delivery Technology 9, n. 01 (9 gennaio 2019): 27–33. http://dx.doi.org/10.25258/ijddt.9.1.5.
Testo completoAbstract (sommario):
Humans have taken advantage of the adaptability of polymers for centuries in the form of resins, gums tars, and oils. However, it was not until the industrial revolution that the modern polymer industry began to develop. Polymers represent an important constituent of pharmaceutical dosage forms. Polymers have played vital roles in the formulation of pharmaceutical products. Polymers have been used as a major tool to manage the drug release rate from the formulations. Synthetic and natural-based polymers have found their way into the biomedical and pharmaceutical industries. Synthetic and Natural polymers can be produced with a broad range of strength, heat resistance, density, stiffness and even price. By constant research into the science and applications of polymers, they are playing an ever-increasing role in society. Diverse applications of polymers in the present pharmaceutical field are for controlled drug release. Based on solubility pharmaceutical polymers can be classified as water-soluble and water-insoluble. In general, the desirable polymer properties in pharmaceutical applications are film forming, adhesion, gelling, thickening, pH-dependent solubility and taste masking. General pharmaceutical applications of polymers in various pharmaceutical formulations are also discussed
33
Wu, Cai-Ying, e Walter A. Aue. "Protected porous polymers". Canadian Journal of Chemistry 67, n. 3 (1 marzo 1989): 389–401. http://dx.doi.org/10.1139/v89-062.
Testo completoAbstract (sommario):
This study was designed to answer the question whether the chromatographic performance of porous polymers — serving here as a model system for pressure-sensitive separation media of relatively large mass transfer resistance — could be improved (a) by imposing on them a chromatographically favorable, extrinsic macrostructure and (b) by protecting that macrostructure against physical deformation. Packed-column gas chromatography was used as the test system.Protected porous polymers (PPP's) were synthesized from pure divinylbenzene (DVB) inside conventional diatomaceous supports, using various amounts and types of porogens. The non-extractable polymer loads ranged from 10 to 40% and conformed to (i.e. formed layers on) the diatomaceous macrostructures. The best plate numbers were in excess of 4000/m on a 100/120 mesh Chromosorb W base. The mass transfer resistance of these materials was very low and permitted high flow rates. The PPP's could be used up to 280 °C and did not appear to suffer deformation; in fact, the polymer appeared to shield the diatom supports from abrasion. The data indicate that the porous polymer deposits had relatively high specific surface areas, and produced a relatively large value for the free energy of sorption per methylene group, as compared with conventional porous polymer beads. Otherwise, protected and unprotected types of porous polymers had similar chromatographic characteristics. Keywords: porous polymer, poly(divinylbenzene), gas chromatography, protected polymer, diatoms.
34
Bahrami, M., M. M. Yovanovich e E. E. Marotta. "Thermal Joint Resistance of Polymer-Metal Rough Interfaces". Journal of Electronic Packaging 128, n. 1 (11 maggio 2005): 23–29. http://dx.doi.org/10.1115/1.2159005.
Testo completoAbstract (sommario):
A compact analytical model is proposed for predicting thermal joint resistance of rough polymer-metal interfaces in a vacuum. The model assumes plastic deformation at microcontacts and joint temperatures less than the polymer’s glassy temperature. The joint resistance includes two components: (i) bulk resistance of the polymer, and (ii) microcontacts resistance, i.e., constriction∕spreading resistance of the microcontacts at the interface. Performing a deformation analysis, it is shown that the deformation mode of surface asperities is plastic for most polymers studied. It is observed that the thermophysical properties of the polymer control the thermal joint resistance and the metallic surface properties have a second order effect on the thermal joint resistance. A new nondimensional parameter, the ratio of microcontacts over bulk thermal resistances, is proposed as a criterion to specify the relative importance of the microcontacts thermal resistance. The present model is compared with more than 140 experimental data points collected for a selected number of polymers. The averaged rms relative difference between the model and data is approximately 12.7%.
35
Singh, Divya, B. Bhattacharya e Hardev Singh Virk. "Conductivity Modulation in Polymer Electrolytes and their Composites due to Ion-Beam Irradiation". Solid State Phenomena 239 (agosto 2015): 110–48. http://dx.doi.org/10.4028/www.scientific.net/ssp.239.110.
Testo completoAbstract (sommario):
Polymers are a class of materials widely used in different fields of applications. With imminent applications of polymers, the study of radiation induced changes in polymers has become an obvious scientific demand. The bombardment by ion beam radiations has become one of the most promising techniques in present day polymer research. When the polymers are irradiated, a variety of physical and chemical changes takes place due to energy deposition of the radiation in the polymer matrix. Scissoring, cross-linking, recombination, radical decomposition, etc. are some of the interesting changes that are obvious in polymers. The modification in polymer properties by irradiation depends mainly on the nature of radiation and the type of polymer used.Polymer electrolytes are obtained by modifying polymers by doping, complexing, or other chemical processes. In general, they suffer from low conductivity due to high crystallinity of the matrix. The effect of radiation on polymer electrolyte is expected to alter their crystalline nature vis-a-vis electrical properties. This review article shall elaborate modifications in the physical and chemical properties of polymer electrolytes and their composites. The variations in properties have been explored on PEO based polymer electrolyte and correlated with the parameters responsible for such changes. Also a comparison with different types of the polymers irradiated with a wide range of ion beams has been established.
36
Kim, Jinsang. "Assemblies of conjugated polymers: Intermolecular and intramolecular effects on the photophysical properties of conjugated polymers". Pure and Applied Chemistry 74, n. 11 (1 gennaio 2002): 2031–44. http://dx.doi.org/10.1351/pac200274112031.
Testo completoAbstract (sommario):
Conjugated polymers are emerging materials for electronic applications due to the tunability of their properties through variation of their chemical structure. Their applications, which currently include light-emitting diodes (LEDs), field effect transistors (FETs), plastic lasers, batteries, and sensors, are expanding to many new areas. The two critical parameters that determine the function of conjugated polymer-based devices are chemical structure and nanostructure of a conjugated polymer in the solid state. While the physical properties of isolated polymers are primarily controlled by their chemical structure, these properties are drastically altered in the solid state due to electronic coupling between polymer chains as determined by their interpolymer packing and conformation. However, the development of effective and precise methods for controlling the nanostructure of polymers in the solid state has been limited because polymers often fail to assemble into organized structures due to their amorphous character and large molecular weight.In this review, recent developments of organizing methods of conjugated polymers and the conformation and interpolymer interaction effects on the photophysical properties of conjugated polymers are summarized.
37
Shen, Yijun, e Kaiwen Wang. "Polymer applications in drug delivery". Journal of Physics: Conference Series 2608, n. 1 (1 ottobre 2023): 012036. http://dx.doi.org/10.1088/1742-6596/2608/1/012036.
Testo completoAbstract (sommario):
Abstract Polymers have been broadly used in consumer goods, drug delivery, formulation, semiconductor, and packaging applications. Generally, polymers would be divided into two categories. The first category is commodity polymers. For instance, many packages of polymers are used daily: LDPE, HDPE, PVC, PE, PS, and PP. Based on the properties of each polymer, applications were adjusted for specific uses. The second category is engineering polymers. For example, PC, PDMS, PET, PA, and POM. This article will discuss polymer applications that mainly focus on drug delivery. Specifically, this article review will conduct a details application of polymers when formulating polymers into drug delivery processes. This review will elaborate on polymer application in control release, oral delivery, transdermal delivery, protein modification, cancer therapy, RNA delivery, and application. This review would also provide a comprehensive review of drug delivery characteristics.
38
Puchnin, Kirill, Dmitriy Ryazantsev, Egor Latipov, Vitaliy Grudtsov e Alexander Kuznetsov. "Off-Stoichiometry Thiol–Ene Polymers: Inclusion of Anchor Groups Using Allylsilanes". Polymers 15, n. 6 (7 marzo 2023): 1329. http://dx.doi.org/10.3390/polym15061329.
Testo completoAbstract (sommario):
The use of polymers in silicon chips is of great importance for the development of microelectronic and biomedical industries. In this study, new silane-containing polymers, called OSTE-AS polymers, were developed based on off-stoichiometry thiol–ene polymers. These polymers can bond to silicon wafers without pretreatment of the surface by an adhesive. Silane groups were included in the polymer using allylsilanes, with the thiol monomer as the target of modification. The polymer composition was optimized to provide the maximum hardness, the maximum tensile strength, and good bonding with the silicon wafers. The Young’s modulus, wettability, dielectric constant, optical transparency, TGA and DSC curves, and the chemical resistance of the optimized OSTE-AS polymer were studied. Thin OSTE-AS polymer layers were obtained on silicon wafers via centrifugation. The possibility of creating microfluidic systems based on OSTE-AS polymers and silicon wafers was demonstrated.
39
Bechtel, Stephan, Rouven Schweitzer, Maximilian Frey, Ralf Busch e Hans-Georg Herrmann. "Material Extrusion of Structural Polymer–Aluminum Joints—Examining Shear Strength, Wetting, Polymer Melt Rheology and Aging". Materials 15, n. 9 (26 aprile 2022): 3120. http://dx.doi.org/10.3390/ma15093120.
Testo completoAbstract (sommario):
Generating polymer–metal structures by means of additive manufacturing offers huge potential for customized, sustainable and lightweight solutions. However, challenges exist, primarily with regard to reliability and reproducibility of the additively generated joints. In this study, the polymers ABS, PETG and PLA, which are common in material extrusion, were joined to grit-blasted aluminum substrates. Temperature dependence of polymer melt rheology, wetting and tensile single-lap-shear strength were examined in order to obtain appropriate thermal processing conditions. Joints with high adhesive strength in the fresh state were aged for up to 100 days in two different moderate environments. For the given conditions, PETG was most suitable for generating structural joints. Contrary to PETG, ABS–aluminum joints in the fresh state as well as PLA–aluminum joints in the aged state did not meet the demands of a structural joint. For the considered polymers and processing conditions, this study implies that the suitability of a polymer and a thermal processing condition to form a polymer–aluminum joint by material extrusion can be evaluated based on the polymer’s rheological properties. Moreover, wetting experiments improved estimation of the resulting tensile single-lap-shear strength.
40
Bechtel, Stephan, Rouven Schweitzer, Maximilian Frey, Ralf Busch e Hans-Georg Herrmann. "Material Extrusion of Structural Polymer–Aluminum Joints—Examining Shear Strength, Wetting, Polymer Melt Rheology and Aging". Materials 15, n. 9 (26 aprile 2022): 3120. http://dx.doi.org/10.3390/ma15093120.
Testo completoAbstract (sommario):
Generating polymer–metal structures by means of additive manufacturing offers huge potential for customized, sustainable and lightweight solutions. However, challenges exist, primarily with regard to reliability and reproducibility of the additively generated joints. In this study, the polymers ABS, PETG and PLA, which are common in material extrusion, were joined to grit-blasted aluminum substrates. Temperature dependence of polymer melt rheology, wetting and tensile single-lap-shear strength were examined in order to obtain appropriate thermal processing conditions. Joints with high adhesive strength in the fresh state were aged for up to 100 days in two different moderate environments. For the given conditions, PETG was most suitable for generating structural joints. Contrary to PETG, ABS–aluminum joints in the fresh state as well as PLA–aluminum joints in the aged state did not meet the demands of a structural joint. For the considered polymers and processing conditions, this study implies that the suitability of a polymer and a thermal processing condition to form a polymer–aluminum joint by material extrusion can be evaluated based on the polymer’s rheological properties. Moreover, wetting experiments improved estimation of the resulting tensile single-lap-shear strength.
41
Chen, Weifeng, Shaona Chen, Weimin Hu, Dejiang Li e Zhongxu Dai. "The Preparation Approaches of Polymer/graphene Nanocomposites and their Appilcation Research Progress as Electrochemical Sensors". Journal of New Materials for Electrochemical Systems 20, n. 4 (31 ottobre 2017): 205–21. http://dx.doi.org/10.14447/jnmes.v20i4.356.
Testo completoAbstract (sommario):
Graphene, a two-dimensional sheet of sp2-hybridized carbon atoms packed into a honeycomb lattice, can be combined with various polymers through different methods and techniques. Polymer/graphene nanocomposites are expected to not only preserve the fa-vorable properties of graphene and polymers, but also greatly enhance the intrinsic properties due to the synergetic effect between them. In this review, the preparation approaches of graphene/polymer nanocomposites, including melt blending, solution blending, in-situ polymeri-zation and in-situ synthesis, were presented comprehensively in order to study the relationship between these approaches and the final characteristics and performances. Each approach had different influences on the final properties of the nanocomposites. The advantages and disadvantages of the preparation methods were discussed respectively. Additionally, the application researches of the polymer/graphene nanocomposites as electrochemical sensors, were introduced in detail. With regard to some important or novel sensors, the mechanisms were proposed for reference. Finally, conclusions were given and the issues waiting to be settled for further development were pointed out. The current review demonstrates that polymer/graphene nanocomposites exhibit superior electrochemical performances and will be applied practically in the field of sensor devices.
42
Schmidt, Bernhard V. K. J. "Hydrophilic Polymers". Polymers 11, n. 4 (16 aprile 2019): 693. http://dx.doi.org/10.3390/polym11040693.
Testo completo
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Khan, Shahab, e Aroosa Iqbal. "Organic polymers revolution: Applications and formation strategies, and future perspectives". Journal of Polymer Science and Engineering 6, n. 1 (15 dicembre 2023): 3125. http://dx.doi.org/10.24294/jpse.v6i1.3125.
Testo completoAbstract (sommario):
The history of organic polymers is a remarkable journey from the discovery of natural materials like rubber and silk to the development of sophisticated synthetic polymers that have transformed industries and modern life. This comprehensive review article presents a detailed account of the evolution of organic polymers. It begins with the early uses of natural polymers and explores key breakthroughs, including the invention of Bakelite, nylon, and neoprene. The theoretical foundations of polymer science, laid by Hermann Staudinger, are discussed, and the post-war surge in polymer development is examined, including the introduction of polyethylene, polypropylene, and PVC. Notable advances in polymer chemistry, such as isotactic polypropylene and silicone polymers, are highlighted. The article also delves into the development of high-performance polymers like Kevlar and carbon-based materials, offering insights into their applications. Moreover, it discusses the current trends in polymer science, emphasizing sustainability and biodegradability. As the world continues to rely on polymers for numerous applications, this review provides a historical perspective and a glimpse into the future of organic polymers, where innovations are expected to shape various aspects of technology, healthcare, and environmental protection.
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Jones, Richard G., Tatsuki Kitayama, Karl-Heinz Hellwich, Michael Hess, Aubrey D. Jenkins, Jaroslav Kahovec, Pavel Kratochvíl et al. "Source-based nomenclature for single-strand homopolymers and copolymers (IUPAC Recommendations 2016)". Pure and Applied Chemistry 88, n. 10-11 (1 novembre 2016): 1073–100. http://dx.doi.org/10.1515/pac-2015-0702.
Testo completoAbstract (sommario):
AbstractIUPAC recommendations on source-based nomenclature for single-strand polymers have so far addressed its application mainly to copolymers, non-linear polymers and polymer assemblies, and within generic source-based nomenclature of polymers. In this document, rules are formulated for devising a satisfactory source-based name for a polymer, whether homopolymer or copolymer, which are as clear and rigorous as possible. Thus, the source-based system for naming polymers is presented in a totality that serves as a user-friendly alternative to the structure-based system of polymer nomenclature. In addition, because of their widespread and established use, recommendations for the use of traditional names of polymers are also elaborated.
45
Rahman, Mijanur, Aliaa Ali, Erica Sjöholm, Sebastian Soindinsalo, Carl-Eric Wilén, Kuldeep Kumar Bansal e Jessica M. Rosenholm. "Significance of Polymers with “Allyl” Functionality in Biomedicine: An Emerging Class of Functional Polymers". Pharmaceutics 14, n. 4 (6 aprile 2022): 798. http://dx.doi.org/10.3390/pharmaceutics14040798.
Testo completoAbstract (sommario):
In recent years, polymer-based advanced drug delivery and tissue engineering have grown and expanded steadily. At present, most of the polymeric research has focused on improving existing polymers or developing new biomaterials with tunable properties. Polymers with free functional groups offer the diverse characteristics needed for optimal tissue regeneration and controlled drug delivery. Allyl-terminated polymers, characterized by the presence of a double bond, are a unique class of polymers. These polymers allow the insertion of a broad diversity of architectures and functionalities via different chemical reactions. In this review article, we shed light on various synthesis methodologies utilized for generating allyl-terminated polymers, macromonomers, and polymer precursors, as well as their post-synthesis modifications. In addition, the biomedical applications of these polymers reported in the literature, such as targeted and controlled drug delivery, improvement i aqueous solubility and stability of drugs, tissue engineering, and antimicrobial coatings, are summarized.
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Butar-butar, Maria, e Anis Chaerunisaa. "Thermal Behavior of Polymers in Solid-State". Sciences of Pharmacy 1, n. 1 (24 giugno 2022): 8–19. http://dx.doi.org/10.58920/sciphar01010008.
Testo completoAbstract (sommario):
A variety of potential polymers with chemical and physical stability characteristics and abundant availability lead to the rapid application of polymers in various fields. One of the crucial things that are crucial to be discussed from such polymers is the characteristic of thermal behavior. Each type of polymer such as natural and synthetic has different thermal characteristics, including Tc, Tg, Tm, and Td which can be the determining factor of polymer selection of processing and application temperature. The thermal properties will also affect molecular interactions, physical stability in manufacturing, distribution, and storage. Therefore, in this article will appoint a study on the thermal characteristics of natural and synthetic polymers, the effect of modification on the thermal properties of polymers, efforts to increase the stability of thermal, and polymer applications in the field of pharmaceutical technology.
47
Miroznicenco, Ana, Gabriel Saracu, Vasile Bria, Mihaela-Claudia Gorovei e Adrian Circiumaru. "Mechanical Properties of PMMA and PLA Modified Epoxy Resins". Materiale Plastice 60, n. 4 (5 gennaio 2024): 167–80. http://dx.doi.org/10.37358/mp.23.4.5696.
Testo completoAbstract (sommario):
Last years research in polymers registered an increase of interest regarding polymer mixtures aiming to obtain materials with properties of the mixed polymers. In this respect many studies are pointing the mixtures between a thermoset polymer and a thermoplastic polymer. It is known the fact that thermoplastic polymers are much more malleable than the thermoset ones and the goal is to obtain a mixture with the general properties of the thermoset polymer and with a machining ability proper to the thermoset polymer. The vitrimers are this type of polymers and, some of them, can be obtained by mixing polymers form the two categories. This study is about using solutions of two thermoset polymers to modify the basic properties of three epoxy resins. The results show that the presence of PMMA, respectively, PLA inside the epoxy resin matrix determines changes of the mechanical properties of the formed materials. Without analysing the adhesive properties of new materials is hard to decide about their value from the composites applications point of view.
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MacDiarmid, Alan G., e Weigong Zheng. "Electrochemistry of Conjugated Polymers and Electrochemical Applications". MRS Bulletin 22, n. 6 (giugno 1997): 24–30. http://dx.doi.org/10.1557/s0883769400033595.
Testo completoAbstract (sommario):
The discovery in 1977–78 that trans-polyacetylene — (CH)x, the prototype conducting polymer (Figure 1)—could be chemically p-doped (partly oxidized) or n-doped (partly reduced) with a concomitant increase of its conductivity through the semiconducting to the metallic regime introduced new concepts of considerable theoretical and possible technological importance to condensed matter science. In 1979 it was discovered that p- or n-doping of trans-(CH)x could be accomplished electrochemically and that these processes were electrochemically reversible. Polyacetylene is the simplest example of a conjugated polymer, a polymer in which the “backbone” atoms are joined alternately by single and double bonds. All conducting polymers, “synthetic metals,” are conjugated polymers, at least in their doped forms. Other conducting polymers, including for example, poly(paraphenylene), polypyrrole, polythiophene, and polyaniline, have since been examined as electrochemically active materials. These findings have stimulated much industrial and academic interest in the electro-chemistry of conducting polymers and their possible technological applications in for example, energy storage, electrochromic displays, electrochemical drug-delivery systems, electromechanical devices, and light-emitting devices.This article will show the relationship between the doping of a conjugated polymer, the reduction potential of the polymer, and the role of “dopant” ions. These interrelationships have frequently caused considerable confusion in understanding electrochemical doping. Electrochemical synthesis of conjugated polymers and the role of cyclic voltammetry in elucidating the mechanism of electrochemical redox processes involving conjugated organic polymers will also be discussed. This article will also summarize a few selected applications involving electro-chemical properties of conjugated polymers. The coverage is intended to beexemplary rather than exhaustive. Furthermore since the electrochemistry of (CH), the “prototype” conducting polymer, has been extensively studied and comprises a relatively simple, reversible electrochemical system, it will be used to exemplify the basic concepts involved. These basic concepts can then be applied with appropriate modification as necessary to the electrochemistry of other conjugated polymers. Polyaniline will then be used to illustrate a more complex conjugated polymer electrochemical system.
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Hu, Jin Lian, e Jing Lu. "Shape Memory Polymers in Textiles". Advances in Science and Technology 80 (settembre 2012): 30–38. http://dx.doi.org/10.4028/www.scientific.net/ast.80.30.
Testo completoAbstract (sommario):
This paper highlight the most important areas and directions of shape memory polymers in textiles. The textiles of shape memory polymers involve fibre spinning (including wet-spinning, melt-spinning and electro-spinning), fabric, smart apparel, actively finishing technology and WVP investigation. Based on the molecular structure of shape memory polymer, the shape memory transformation from polymer to textiles and application theory are illustrated and stated. Additionally, the challenges of shape memory polymers in textiles are pointed out and some research directions are also suggested in this paper.
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Rayung, Marwah, Min Min Aung, Shah Christirani Azhar, Luqman Chuah Abdullah, Mohd Sukor Su’ait, Azizan Ahmad e Siti Nurul Ain Md Jamil. "Bio-Based Polymer Electrolytes for Electrochemical Devices: Insight into the Ionic Conductivity Performance". Materials 13, n. 4 (12 febbraio 2020): 838. http://dx.doi.org/10.3390/ma13040838.
Testo completoAbstract (sommario):
With the continuing efforts to explore alternatives to petrochemical-based polymers and the escalating demand to minimize environmental impact, bio-based polymers have gained a massive amount of attention over the last few decades. The potential uses of these bio-based polymers are varied, from household goods to high end and advanced applications. To some extent, they can solve the depletion and sustainability issues of conventional polymers. As such, this article reviews the trends and developments of bio-based polymers for the preparation of polymer electrolytes that are intended for use in electrochemical device applications. A range of bio-based polymers are presented by focusing on the source, the general method of preparation, and the properties of the polymer electrolyte system, specifically with reference to the ionic conductivity. Some major applications of bio-based polymer electrolytes are discussed. This review examines the past studies and future prospects of these materials in the polymer electrolyte field.