Journal articles on the topic 'Pointe polymère'
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1
Pelletier, H., C. Gauthier, and R. Schirrer. "Analyses des sillons viscoélastiques lors d'un contact entre une pointe rigide et la surface d'un polymère." Matériaux & Techniques 96, no. 3 (2008): 111–20. http://dx.doi.org/10.1051/mattech:2008026.
2
Chen, Weifeng, Shaona Chen, Weimin Hu, Dejiang Li, and 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, no. 4 (October 31, 2017): 205–21. http://dx.doi.org/10.14447/jnmes.v20i4.356.
Abstract:
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.
3
Ma, Liang. "Comparing the Principles of Reversible Covalent Chemistry and Supramolecular Chemistry Points to New Directions in the Development of Polymers." Highlights in Science, Engineering and Technology 26 (December 30, 2022): 446–54. http://dx.doi.org/10.54097/hset.v26i.4025.
Abstract:
Polymers are some of the most widely used materials for human use and have greatly facilitated people's lives. However, with the use of polymer materials, traditional thermoplastic and thermoset materials are unable to meet the more diverse needs, and traditional processing methods are not able to significantly improve the performance of polymer materials. Some researchers have found that by applying the principles of reversible covalent and supramolecular chemistry in dynamic chemistry in the development of polymers, the properties and functions of polymers can be changed from the bottom up. Therefore, this paper analyses the similarities and differences between the principles of reversible covalent chemistry and supramolecular chemistry by collecting applications of reversible covalent chemistry and supramolecular chemistry in the field of polymer synthesis and comparing the two to provide assistance for future developments in the field of polymers.
4
Hu, Jin Lian, and Jing Lu. "Shape Memory Polymers in Textiles." Advances in Science and Technology 80 (September 2012): 30–38. http://dx.doi.org/10.4028/www.scientific.net/ast.80.30.
Abstract:
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.
5
Valenzuela, Loreto M., Doyle D. Knight, and Joachim Kohn. "Developing a Suitable Model for Water Uptake for Biodegradable Polymers Using Small Training Sets." International Journal of Biomaterials 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/6273414.
Abstract:
Prediction of the dynamic properties of water uptake across polymer libraries can accelerate polymer selection for a specific application. We first built semiempirical models using Artificial Neural Networks and all water uptake data, as individual input. These models give very good correlations (R2>0.78for test set) but very low accuracy on cross-validation sets (less than 19% of experimental points within experimental error). Instead, using consolidated parameters like equilibrium water uptake a good model is obtained (R2=0.78for test set), with accurate predictions for 50% of tested polymers. The semiempirical model was applied to the 56-polymer library of L-tyrosine-derived polyarylates, identifying groups of polymers that are likely to satisfy design criteria for water uptake. This research demonstrates that a surrogate modeling effort can reduce the number of polymers that must be synthesized and characterized to identify an appropriate polymer that meets certain performance criteria.
6
Zore, Ashish, Peng Geng, Yuwei Zhang, and Michael R. Van De Mark. "Defining the Collapse Point in Colloidal Unimolecular Polymer (CUP) Formation." Polymers 14, no. 9 (May 7, 2022): 1909. http://dx.doi.org/10.3390/polym14091909.
Abstract:
Colloidal unimolecular polymer (CUP) particles were made using polymers with different ratios of hydrophobic and hydrophilic monomers via a self-organization process known as water reduction. The water-reduction process and the collapse of the polymer chain to form a CUP were tracked using viscosity measurements as a function of composition. A vibration viscometer, which allowed for viscosity measurement as the water was being added during the water-reduction process, was utilized. The protocol was optimized and tested for factors such as temperature control, loss of material, measurement stability while stirring, and changes in the solution volume with the addition of water. The resulting viscosity curve provided the composition of Tetrahydrofuran (THF)/water mixture that triggers the collapse of a polymer chain into a particle. Hansen as well as dielectric parameters were related to the polymer composition and percentage v/v of THF/water mixture at the collapse point. It was observed that the collapse of the polymer chain occurred when the water/THF composition was at a water volume of between 53.8 to 59.3% in the solvent mixture.
7
Browne, Emer, Zelalem A. Worku, and Anne Marie Healy. "Physicochemical Properties of Poly-vinyl Polymers and Their Influence on Ketoprofen Amorphous Solid Dispersion Performance: A Polymer Selection Case Study." Pharmaceutics 12, no. 5 (May 8, 2020): 433. http://dx.doi.org/10.3390/pharmaceutics12050433.
Abstract:
When developing an amorphous solid dispersion (ASD), a prudent choice of polymer is critical to several aspects of ASD performance including: processability, solid state stability and dissolution rate. However, there is little guidance available to formulators to aid judicious polymer selection and a “trial and error” approach is often taken. This study aims to facilitate rational polymer selection and formulation design by generating ASDs using a range of poly-vinyl polymers and ketoprofen as a model active pharmaceutical ingredient (API) and evaluating several aspects of their performance. The molecular weight of the polymer and the ratio of vinyl pyrrolidone to vinyl acetate in the polymer were found to influence the relative humidity at which the relative humidity induced glass transition occurred, as well as the extent of ketoprofen supersaturation achieved during dynamic solubility testing. Interestingly, ASD tablets containing polymers with the vinyl pyrrolidone functional group exhibited higher tensile strengths than those without. This points towards the binder functionality of vinyl pyrrolidone. In conclusion, the physicochemical properties of poly-vinyl polymers greatly influence ketoprofen ASD performance and due regard should be paid to these properties in order to develop an ASD with the desired attributes.
8
Nizina, T. A., Dmitrii R. Nizin, N. S. Kanaeva, N. M. Kuznetsov, and D. A. Artamonov. "Applying the Fractal Analysis Methods for the Study of the Mechanisms of Deformation and Destruction of Polymeric Material Samples Affected by Tensile Stresses." Key Engineering Materials 799 (April 2019): 217–22. http://dx.doi.org/10.4028/www.scientific.net/kem.799.217.
Abstract:
The paper proposes an approach to study the mechanism of deformation of epoxy polymers based on the methods of fractal calculations. The advantages of the method for determining the fractality index of the deformation curves of polymer samples using the minimum coverage method are shown. An algorithm for the quantitative determination of the location of the "critical" points of the deformation curves of polymer samples under tension is proposed. It is shown that the use of the developed methodology for the fractal analysis of time series on the basis of a set of points of deformation curves of epoxy polymer samples under tension, provides valuable information about the processes occurring in the structure of composite materials affected by mechanical loads and various aggressive factors.
9
Peram, Shyamsundar Reddy, Madhava Rao Byraboina, Narendran Dama, Suryanarayana Murthy Kurivella, and Jagadish Mandava. "An Overview of Thermal Behavior of Polymers: Lead Acid Battery Applications." European Journal of Engineering and Technology Research 7, no. 1 (January 10, 2022): 12–17. http://dx.doi.org/10.24018/ej-eng.2022.7.1.2704.
Abstract:
Thermal analysis is the analysis of a change in a property of a material, which is related to the temperature difference. Polymer samples are typically in solid form and undergo various thermal transitions upon heating, including melting, phase transition, sublimation, and decomposition. The purpose of this study is to demonstrate how thermal techniques such as DSC and TGA may be used to evaluate polymer thermal stability through the examination of polymer characteristics such as glass transition temperatures, melting points, and mass changes. Different polymers have been investigated and used in lead-acid batteries for various applications based on their mechanical and thermal characteristics. Few lead-acid battery-related polymers like Polypropylene (PP), Polyethylene (PE) Separator, Polyethylene Terephthalate (PET), Polyvinyl Chloride (PVC) and Acrylonitrile butadiene styrene (ABS) were studied and explained.
10
Peram, Shyamsundar Reddy, Madhava Rao Byraboina, Narendran Dama, Suryanarayana Murthy Kurivella, and Jagadish Mandava. "An Overview of Thermal Behavior of Polymers: Lead Acid Battery Applications." European Journal of Engineering and Technology Research 7, no. 1 (January 10, 2022): 12–17. http://dx.doi.org/10.24018/ejeng.2022.7.1.2704.
Abstract:
Thermal analysis is the analysis of a change in a property of a material, which is related to the temperature difference. Polymer samples are typically in solid form and undergo various thermal transitions upon heating, including melting, phase transition, sublimation, and decomposition. The purpose of this study is to demonstrate how thermal techniques such as DSC and TGA may be used to evaluate polymer thermal stability through the examination of polymer characteristics such as glass transition temperatures, melting points, and mass changes. Different polymers have been investigated and used in lead-acid batteries for various applications based on their mechanical and thermal characteristics. Few lead-acid battery-related polymers like Polypropylene (PP), Polyethylene (PE) Separator, Polyethylene Terephthalate (PET), Polyvinyl Chloride (PVC) and Acrylonitrile butadiene styrene (ABS) were studied and explained.
11
Pan, Yi, Xianglong Cui, Hao Wang, Xu Lou, Shuangchun Yang, and Famuwagun Felix Oluwabusuyi. "Research Progress of Intelligent Polymer Plugging Materials." Molecules 28, no. 7 (March 27, 2023): 2975. http://dx.doi.org/10.3390/molecules28072975.
Abstract:
Intelligent polymers have become the focus of attention worldwide. Intelligent polymer materials through organic synthesis methods are used to make inanimate organic materials become “feeling” and “sentient”. Intelligent polymer materials have been applied in actual engineering production, and they are becoming a new research topic for scientists in various fields and countries, especially in the areas of drilling and plugging. The development of intelligent polymer materials can provide new solutions and technical means for drilling and plugging. Unlike traditional plugging materials, intelligent polymer plugging materials can cope with environmental changes. They have the characteristics of a strong target, good plugging effect, and no damage to the reservoir. However, there are currently no reviews on intelligent polymer plugging materials in the drilling field, so this paper fills that gap by reviewing the research progress of intelligent polymer plugging materials. In addition, this paper describes the mechanism and application status of intelligent polymer shape-memory polymers, intelligent polymer gels, intelligent polymer membranes, and intelligent polymer bionic materials in drilling and plugging. It is also pointed out that some intelligent polymer plugging materials still have problems, such as insufficient toughness and a poor resistance to salt and high temperature. At the same time, some suggestions for future research directions are also presented for reference.
12
Wall, B. G., J. L. Koenig, R. Bhargava, and C. M. Snively. "FTIR Imaging of Multiphase Polymer Systems." Microscopy and Microanalysis 5, S2 (August 1999): 992–93. http://dx.doi.org/10.1017/s1431927600018286.
Abstract:
Fourier Transform Infrared (FTIR) Microspectroscopy is a powerful method to examine and characterize domains down to areas of 10х10 μm2. Spatial concentration maps of chemical species were obtained using apertures to sequentially examine areas on a grid and obtain a map by plotting average spectral absorbance data obtained from each of the areas. New Focal Plane Array (FPA) detectors, composed of a large number (in our case, 64х64) of small detectors arranged in a grid pattern, allow simultaneous collection of infrared radiation at many points from a large spatial region (500х500 μm2 in our case). This allows for a rapid acquisition of chemically specific images from a given area and the examination of several real-time processes. This technique has found a wide variety of applications in multi-phase polymers including polymer laminates, phase separated polymer composites, semi-crystalline polymers and blends, and solvent diffusion into polymers have been the main areas of interest in non-biological IR studies using FPA detection. We present some of the recent work in our group on various multi-phase polymer systems using FPA based infrared spectroscopy.
13
Kryczka, T., P. Grieb, M. Bero, J. Kasperczyk, and P. Dobrzynski. "Kinetics of a nucleoside release from lactide-caprolactone and lactide-glycolide polymers in vitro." Acta Biochimica Polonica 47, no. 1 (March 31, 2000): 59–64. http://dx.doi.org/10.18388/abp.2000_4062.
Abstract:
We assessed the rate of release of a model nucleoside (adenosine, 5%, w/w) from nine different lactide-glycolide or lactide-caprolactone polymers. The polymer discs were eluted every second day with an artificial cerebrospinal fluid at the elution rate roughly approximating the brain extracellular fluid formation rate. Adenosine in eluate samples was assayed by HPLC. Three polymers exhibited a relatively constant release of adenosine for over four weeks, resulting in micromolar concentrations of nucleoside in the eluate. This points to the necessity of further development of polymers of this types as intracerebral nucleoside delivery systems for local treatment of brain tumors.
14
Guseva, M. A., L. A. Prokopova, and М. A. Khaskov. "Determination of the melting point of solid polymers by rheological method." Industrial laboratory. Diagnostics of materials 87, no. 7 (July 24, 2021): 38–43. http://dx.doi.org/10.26896/1028-6861-2021-87-7-38-43.
Abstract:
The rheological properties of polymer systems determine their deformation behavior and the relationship between stresses, strains and strain rates. We present the results of determining the melting points of solid polymer compounds by the rheological method. Tests were carried out using a rotary rheometer in an oscillating mode. Using the obtained thermomechanical dependences, the experimental data were compared with the values determined by standard analytical (capillary method) and thermal (differential scanning calorimetry) methods. The viscous and elastic behavior of the samples were analyzed using the dependence of the oscillating stress or strain on the angular velocity or frequency. It is shown that the temperature dependences of the storage and loss moduli, as well as the angle of mechanical losses, determine the physical and relaxation transitions in polymers upon their heating. The obtained results can be used in analysis of the effect of conditions of polymer processing on their properties, as well as in optimization of the technological processes of product manufacture and modeling the behavior of materials under operation conditions at the stage of development.
15
Kumar, Avishek, Ahmed Al-Jumaili, Kateryna Bazaka, Peter Mulvey, Jeffrey Warner, and Mohan V. Jacob. "In-Situ Surface Modification of Terpinen-4-ol Plasma Polymers for Increased Antibacterial Activity." Materials 13, no. 3 (January 27, 2020): 586. http://dx.doi.org/10.3390/ma13030586.
Abstract:
Surface modification of thin films is often performed to enhance their properties. In this work, in situ modification of Terpinen-4-ol (T4) plasma polymer is carried out via simultaneous surface functionalization and nanoparticle immobilization. Terpinen-4-ol plasma polymers surface were decorated with a layer of ZnO nanoparticles in an oxygen plasma environment immediately after polymer deposition. A combination of hydrophilic modification and ZnO nanoparticle functionalization of the T4 polymer surface led to an enhancement in antibacterial properties by factor of 3 (from 0.75 to 0.25 CFU.mm−2). In addition, ZnO nanoparticle-modified coatings demonstrated improved UV absorbing characteristics in the region of 300–400 nm by 60% relative to unmodified coatings. The ZnO modified coatings were transparent in the visible region of 400–700 nm. The finding points towards the potential use of ZnO nanoparticle-modified T4 plasma polymers as optically transparent UV absorbing coatings.
16
Zhao, Yaoli, Patatri Chakraborty, Nicholas Stavinski, Luis Velarde, Vaishali Maheshkar, Karthik Dantu, Arindam Phani, Seonghwan Kim, and Thomas Thundat. "Standoff and Point Detection of Thin Polymer Layers Using Microcantilever Photothermal Spectroscopy." Journal of The Electrochemical Society 169, no. 3 (March 1, 2022): 037501. http://dx.doi.org/10.1149/1945-7111/ac5657.
Abstract:
Standoff detection based on optical spectroscopy is an attractive method for identifying materials at a distance with very high molecular selectivity. Standoff spectroscopy can be exploited in demanding practical applications such as sorting plastics for recycling. Here, we demonstrate selective and sensitive standoff detection of polymer films using bi-material cantilever-based photothermal spectroscopy. We demonstrate that the selectivity of the technique is sufficient to discriminate various polymers. We also demonstrate in situ, point detection of thin layers of polymers deposited on bi-material cantilevers using photothermal spectroscopy. Comparison of the standoff spectra with those obtained by point detection, FTIR, and FTIR-ATR show relative broadening of peaks. Exposure of polymers to UV radiation (365 nm) reveal that the spectral peaks do not change with exposure time, but results in peak broadening with an overall increase in the background cantilever response. The sensitivity of the technique can be further improved by optimizing the thermal sensitivity of the bi-material cantilever and by increasing the number of photons impinging on the cantilever.
17
de França, Juliene Oliveira Campos, Deborah da Silva Valadares, Mateus Freitas Paiva, Sílvia Cláudia Loureiro Dias, and José Alves Dias. "Polymers Based on PLA from Synthesis Using D,L-Lactic Acid (or Racemic Lactide) and Some Biomedical Applications: A Short Review." Polymers 14, no. 12 (June 8, 2022): 2317. http://dx.doi.org/10.3390/polym14122317.
Abstract:
Poly(lactic acid) (PLA) is an important polymer that is based on renewable biomass resources. Because of environmental issues, more renewable sources for polymers synthesis have been sought for industrial purposes. In this sense, cheaper monomers should be used to facilitate better utilization of less valuable chemicals and therefore granting more sustainable processes. Some points are raised about the need to study the total degradability of any PLA, which may require specific composting conditions (e.g., temperature, type of microorganism, adequate humidity and aerobic environment). Polymerization processes to produce PLA are presented with an emphasis on D,L-lactic acid (or rac-lactide) as the reactant monomer. The syntheses involving homogeneous and heterogeneous catalytic processes to produce poly(D,L-Lactic acid) (PDLLA) are also addressed. Additionally, the production of blends, copolymers, and composites with PDLLA are also presented exemplifying different preparation methods. Some general applications of these materials mostly dedicated to the biomedical area over the last 10–15 years will be pointed out.
18
Lee, Yi-Chang, Ho Chang, Ching-Long Wei, Rahnfong Lee, Hua-Yi Hsu, and Cheng-Chung Chang. "Determination of deformation of a highly oriented polymer under three-point bending using finite element analysis." e-Polymers 17, no. 1 (January 1, 2017): 83–88. http://dx.doi.org/10.1515/epoly-2016-0248.
Abstract:
AbstractThe molecular chains of a highly oriented polymer lie in the same direction. A highly oriented polymer is an engineering material with a high strength-to-weight ratio and favorable mechanical properties. Such an orthotropic material has biaxially arranged molecular chains that resist stress in the tensile direction, giving it a high commercial value. In this investigation, finite element analysis (FEA) was utilized to elucidate the deformation and failure of a highly oriented polymer. Based on the principles of material mechanics and using the FEA software, Abaqus, a solid model of an I-beam was constructed, and the lengths of this beam were set based on their heights. Three-point bending tests were performed to simulate the properties of the orthotropic highly oriented polymer, yielding results that reveal both tension failure and shear failure. The aspect ratio that most favored the manufacture of an I-beam from highly oriented polymers was obtained; based on this ratio, a die drawing mold can be developed in the future.
19
Dullaert, Konraad, Gerard van Doremaele, Martin van Duin, and Herman Dikland. "QUANTITATIVE ASSESSMENT OF THE BRANCHING ARCHITECTURE OF EPDM WITH HIGH CONTENT OF 5-VINYL-2-NORBORNENE AS THIRD MONOMER." Rubber Chemistry and Technology 86, no. 4 (December 1, 2013): 503–20. http://dx.doi.org/10.5254/rct.13.87946.
Abstract:
ABSTRACT The branching architecture of high-molecular-weight EPDM polymers with high amounts of 5-vinyl-2-norbornene (VNB) as a third monomer, produced using recently developed Keltan ACE™ technology, was assessed by means of the dilution rheology method proposed by Crosby et al.1 and compared with conventional Ziegler–Natta EPDM grades. First, the dilution rheology results were converted into a single convenient parameter, called the dilution slope. Next, by combining the dilution rheology results with gel permeation chromatography data and assuming trifunctional branching points, we calculated the volume fraction of the branched polymer, the average molecular weight between branching points, and the branching density. It is shown that the high-VNB polymers studied contained a significantly higher amount of branch-on-branch structures.
20
Ahagon, Asahiro. "Molecular Weight Defined in Sol-Gel Analysis and Its Application to Evaluate Branching." Rubber Chemistry and Technology 68, no. 2 (May 1, 1995): 287–96. http://dx.doi.org/10.5254/1.3538743.
Abstract:
Abstract It is considered that many “linear” polymers are actually branched; however, it is difficult to show this with ordinary methods for an arbitrarily chosen polymer. Branching can be regarded as premature crosslinking below the gel point. Attention is then paid to the well-established Charlesby-Pinner Equation used for sol-gel analysis in crosslinking studies. It contains the number average degree of polymerization before crosslinking as a parameter. The molecular parameter is considered here to be that of the virtual linear polymer which would be obtained by unlinking any branch points contained in the polymer. Evidence is shown to support this. It is then possible to estimate the total number of linear components on an average molecule of a branched polymer by taking the ratio of the number average molecular weight measured by two methods, i.e., sol-gel analysis and an ordinary method like GPC. Further information about the branching structure can be obtained by additional measurements of effective crosslink density for a series of polymers obtained from similar polymerization processes.
21
Aldana, Maximino, Miguel Fuentes-Cabrera, and Martín Zumaya. "Self-Propulsion Enhances Polymerization." Entropy 22, no. 2 (February 22, 2020): 251. http://dx.doi.org/10.3390/e22020251.
Abstract:
Self-assembly is a spontaneous process through which macroscopic structures are formed from basic microscopic constituents (e.g., molecules or colloids). By contrast, the formation of large biological molecules inside the cell (such as proteins or nucleic acids) is a process more akin to self-organization than to self-assembly, as it requires a constant supply of external energy. Recent studies have tried to merge self-assembly with self-organization by analyzing the assembly of self-propelled (or active) colloid-like particles whose motion is driven by a permanent source of energy. Here we present evidence that points to the fact that self-propulsion considerably enhances the assembly of polymers: self-propelled molecules are found to assemble faster into polymer-like structures than non self-propelled ones. The average polymer length increases towards a maximum as the self-propulsion force increases. Beyond this maximum, the average polymer length decreases due to the competition between bonding energy and disruptive forces that result from collisions. The assembly of active molecules might have promoted the formation of large pre-biotic polymers that could be the precursors of the informational polymers we observe nowadays.
22
Rondinella, Alfredo, Francesco Andreatta, Daniele Turrin, and Lorenzo Fedrizzi. "Degradation Mechanisms Occurring in PTFE-Based Coatings Employed in Food-Processing Applications." Coatings 11, no. 11 (November 20, 2021): 1419. http://dx.doi.org/10.3390/coatings11111419.
Abstract:
The application of polytetrafluoroethylene (PTFE) coatings to metal surfaces is a well-known procedure carried out to avoid fouling phenomena on food-processing surfaces. Fluorine-based polymers are generally chemically and thermally stable, thus allowing them to be the preferred choice when designing anti-stick coatings in the food service industry. Their lifespan, however, depends on the environmental conditions. It is well known that thermal ageing can affect the properties of PTFE polymers and reduce their mechanical, thermal, and chemical properties causing failures and contaminating food. The main goal of the study is to identify the different failure mechanisms occurring in PTFE-based coatings, using both SEM/EDXS and ATR FT-IR data to reveal the starting point of degradation phenomena in food processing applications. The results from this research reveal that the preferential points for failures are mainly the polymer/substrate interfaces, the polymer/filler interfaces, or the polymer matrix itself.
23
Zheng, Jiaojiao, Jing Zhang, Fengniu Lu, Yi Du, Ding Cao, Shui Hu, Yang Yang, and Zhiqin Yuan. "Visualization of Polymer–Surfactant Interaction by Dual-Emissive Gold Nanocluster Labeling." Biosensors 12, no. 9 (August 26, 2022): 686. http://dx.doi.org/10.3390/bios12090686.
Abstract:
Polymer-surfactant interaction decides the performance of corresponding complexes, making its rapid and intuitionistic visualization important for enhancing the performance of products and/or processing in related fields. In this study, the fluorescence visualization of the interaction between cationic hyperbranched polyethyleneimine and anionic sodium dodecyl sulfonate surfactant was realized by dual-emissive gold nanocluster labeling. The sensing mechanism was due to the interaction-induced polymer conformation change, which regulated the molecular structure and subsequent photoradiation process of the gold nanoclusters. All three inflection points of the interactions between the polymers and the surfactants were obtained by the change in fluorescence emission ratio of the designed dual-emissive gold nanoclusters. Moreover, these inflection points are verified by the hydrodynamic diameter and zeta potential measurements.
24
Afio, Ayarema, Komlan Lolo, Kodjo Attipou, Komla Assogba Kassegne, and Sonnou Tiem. "DYNAMIC THREE-POINTS-BENDING TEST MODE OF TWO AMORPHOUS POLYMER MATERIALS (PMMA, PC) FOR THEIR VISCOELASTIC AND MECHANICAL CHARACTERIZATION." International Journal of Advanced Research 9, no. 08 (August 31, 2021): 448–53. http://dx.doi.org/10.21474/ijar01/13287.
Abstract:
This paper presents an approach to classifying amorphous polymer materials. Temperature is This classiï¬ÂÂcation involves the determination of mechanical and viscoelastic characteristics considered a descriptive variable to clarify the speciï¬ÂÂc ï¬ÂÂeld of practical applications of amorphous polymers. according to the reference temperature characterizing the behaviour of polymer materials. The mechanical and viscoelastic characteristics of amorphous polymers such as methyl poly-methacrylate (PMMA), polycarbonate (PC) and imide poly ether (PEI) are determined through the three-point dynamically embedded test carried out in an adiabatic close enclosure. The complex dissipative or conservative modules according to the temperature are represented. The results obtained show that the fluidity index of these materials is linked to their viscosity, which is a determining property which is decisive for the choice of the technique of the application of the material. Our method of measuring properties is therefore, in principle, comparable to the techniques used in industrial development.
25
Ali Kadhim Mohammed1 and Moayad N. Khalaf. "Synthesis And Characterization Of Copolymers As Pour Point Depressants And Viscosity Index Improvers For Lubricating Oil." Journal of Kufa for Chemical Sciences 2, no. 9 (August 28, 2023): 264–85. http://dx.doi.org/10.36329/jkcm/2022/v2.i9.13298.
Abstract:
poly (1-hexene-co-maleic anhydride) was prepared by free radical polymerization of maleic anhydride with 1-hexene. 1- tetradecanol and 1-hexadecanol were reacted with the poly(l-hexene-co-maleic anhydride)to produce poly (1-hexene-co-ditetraclecyl maleate) and poly (1-hexene-co-dihexadecyl maleate) respectively . Poly (methyl methacrylate-co-maleic anhydride) was prepared from the reaction maleic anhydride with methyl methacrylate by free radical polymerization, then the resulting polymer was reacted with 1-tetradecanol to give poly(methyl methacrylate-co-maleic anhydride). the three prepared polymers was characterized by FTIR and HNMR spectroscopy, while the thermal stability and molecular weight measured by Thermogravimetric analysis TGA and Gel permeation chromatography GPC. the prepared polymers was used to improves the pour point depressant and viscosity index for three base oils from Dura Refinery. the results show the efficiency of the three polymers to improve the pour point and Viscosity index of the base oil
26
Zhang, Xinyang, Xinyang Wang, Jian Li, Shuo Zhang, Qingxin Zhang, and Xiaoyan Yu. "Synthesis of Pyridine Heterocyclic Low-Melting-Point Phthalonitrile Monomer and the Effects of Different Curing Agents on Resin Properties." Polymers 14, no. 21 (November 3, 2022): 4700. http://dx.doi.org/10.3390/polym14214700.
Abstract:
A phthalonitrile monomer (DPTP) containing pyridine with sulfide bonds was prepared and cured into polymers using different curing agents under the same temperature-programmed process. We characterized and comprehensively evaluated the effects of different curing agents on the thermal and thermomechanical properties of phthalonitrile resin, showing that the DPTP monomer cured with naphthalene-containing curing agent exhibited the best performance among the three polymers. Differential scanning calorimetric (DSC) investigation manifested that the melting point of the DPTP monomer was 61 °C, with a processing window of about 170 °C, suggesting the presence of a wide processing range. Thermogravimetric analysis (TGA) demonstrated the outstanding heat resistance, T5%, of 460 °C in nitrogen, at the same time demonstrating superior long-term stability compared with other commonly used polymer materials, which proves the long-term usage under high temperatures of 300 °C. Dynamic mechanical analysis (DMA) revealed that the storage modulus at 50 °C was 3315 MPa, and the glass transition temperature (Tg) of the polymer was more than 350 °C. Therefore, DPTP resins have favorable thermal stability as well as prominent thermomechanical properties.
27
Arsenie, Laura, Franziska Hausig, Carolin Kellner, Johannes Brendel, Patrick Lacroix-Desmazes, Vincent Ladmiral, and Sylvain Catrouillet. "Stimuli-Responsive Thiomorpholine Oxide-Derived Polymers with Tailored Hydrophilicity and Hemocompatible Properties." Molecules 27, no. 13 (June 30, 2022): 4233. http://dx.doi.org/10.3390/molecules27134233.
Abstract:
Thermo-responsive hydrophilic polymers, including those showing tuneable lower critical solution temperature (LCST), represent a continuous subject of exploration for a variety of applications, but particularly in nanomedicine. Since biological pH changes can inform the organism about the presence of disequilibrium or diseases, the development of dual LCST/pH-responsive hydrophilic polymers with biological potential is an attractive subject in polymer science. Here, we present a novel polymer featuring LCST/pH double responsiveness. The monomer ethylthiomorpholine oxide methacrylate (THOXMA) can be polymerised via the RAFT process to obtain well-defined polymers. Copolymers with hydroxyethyl methacrylate (HEMA) were prepared, which allowed the tuning of the LCST behaviour of the polymers. Both, the LCST behaviour and pH responsiveness of hydrophilic PTHOXMA were tested by following the evolution of particle size by dynamic light scattering (DLS). In weak and strong alkaline conditions, cloud points ranged between 40–60 °C, while in acidic medium no LCST was found due to the protonation of the amine of the THOX moieties. Additional cytotoxicity assays confirmed a high biocompatibility of PTHOXMA and haemolysis and aggregation assays proved that the thiomorpholine oxide-derived polymers did not cause aggregation or lysis of red blood cells. These preliminary results bode well for the use of PTHOXMA as smart material in biological applications.
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Raimo, Maria. "Impact of Thermal Properties on Crystalline Structure, Polymorphism and Morphology of Polymer Matrices in Composites." Materials 14, no. 9 (April 22, 2021): 2136. http://dx.doi.org/10.3390/ma14092136.
Abstract:
Morphological analysis at different levels is fundamental to understand properties of materials, as these latter are dictated not only by the chemical composition but also by the shape. Solid structures arise from a balance between thermodynamic and kinetic factors, which, especially for polymer composites, depend also on interactions amongst components. In particular, morphology is strongly affected by the heat transfer pattern during crystallization and by the difference in thermal behavior between polymer matrix and filler. Polymers show a spherulitic structure, arising from the start of crystallization in several points of the liquid phase. Within a general rounded shape, spherulites show variability in growth patterns, morphology, and geometry of boundaries. The appearance and the number of spherulites, as well as their growth mechanism, may vary not only in dependence of the chemical composition and the crystalline structures but also, for a same polymer, in consequence of experimental conditions and incorporation of fillers. This article reviews the crystallization process of polymer matrices in the framework of crystal growth and heat transport theories, and explains microstructural differences between composites and neat matrices on the basis of the differences in thermal capacity and conductivity between polymers and additives.
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Sgambitterra, Emanuele, and Leonardo Pagnotta. "Permeability: The Driving Force That Influences the Mechanical Behavior of Polymers Used for Hydrogen Storage and Delivery." Energies 17, no. 9 (May 4, 2024): 2216. http://dx.doi.org/10.3390/en17092216.
Abstract:
This article explores the main mechanisms that can generate damage in polymers and polymer-based materials used for hydrogen storage and distribution infrastructures. All of these mechanisms are driven by the permeability process that is enhanced by the operating temperature and pressure conditions. Hydrogen storage and delivery systems typically work under high pressure and a relatively wide range of temperatures, especially during the filling and emptying processes. Therefore, it is of great interest to better understand how this phenomenon can influence the integrity of polymer-based hydrogen infrastructures in order to avoid catastrophic events and to better design/investigate new optimized solutions. The first part of this paper discusses the main storage and delivery solutions for gas and liquid hydrogen. Then, the physics of the permeability is investigated with a focus on the effect of pressure and temperature on the integrity of polymers working in a hydrogen environment. Finally, the main mechanisms that mostly induce damage in polymers operating in a hydrogen environment and that influence their mechanical properties are explored and discussed. Particular focus was placed on the rapid gas decompression and aging phenomena. In addition, some of the limits that still exist for a reliable design of polymer-based storage and delivery systems for hydrogen are pointed out.
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Bahrami, M., M. M. Yovanovich, and E. E. Marotta. "Thermal Joint Resistance of Polymer-Metal Rough Interfaces." Journal of Electronic Packaging 128, no. 1 (May 11, 2005): 23–29. http://dx.doi.org/10.1115/1.2159005.
Abstract:
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%.
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Hong, Shi, and Zhu Qing. "Microwave Technology Based Polymer Process." Applied Mechanics and Materials 484-485 (January 2014): 132–36. http://dx.doi.org/10.4028/www.scientific.net/amm.484-485.132.
Abstract:
In this paper the author summarizes the application of microwave techniques in the bulk polymerization, solution polymerization, emulsion polymerization and functional polymer. It is pointed out that the microwave technology can reduce the time and energy consumptions of the polymerization reaction, and improve the properties of polymeric reaction rate, yield and selectivity, which will play an important role in the green chemistry synthesis of polymers.
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JU, JUNG JIN, SEUNG KOO PARK, JUNG YUN DO, SUNTAK PARK, MIN-SU KIM, JONGBAE KIM, and MYUNG-HYUN LEE. "QUASI-PHASE-MATCHED SECOND-HARMONIC GENERATION IN NONLINEAR OPTICAL POLYMER WAVEGUIDE." Journal of Nonlinear Optical Physics & Materials 13, no. 03n04 (December 2004): 383–89. http://dx.doi.org/10.1142/s0218863504002328.
Abstract:
We address issues related to quasi-phase-matched (QPM) second-harmonic generation (SHG) in nonlinear polymer waveguide for applying at optical communication. This field of research is very challenging because the high nonlinearity of polymers leads the device to operate at low pump power levels. However, key problems to this approach include difficulty of phase matching, the high propagation losses of the guided waves, and low nonlinearity contrast in the +/0 type QPM geometry. By optimizing these points on material development, waveguide design, and device fabrication, we demonstrate a QPM SHG with the best efficiency in polymer waveguide.
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Smith, Stephanie A., Jillian Huyck, Sharon H. Choi, and James H. Morrissey. "The Various Procoagulant Effects of PolyP Require Different Minimal Polymer Lengths." Blood 110, no. 11 (November 16, 2007): 1761. http://dx.doi.org/10.1182/blood.v110.11.1761.1761.
Abstract:
Abstract Introduction: Polyphosphates (polyP) are negatively charged, linear phosphate polymers found throughout biology. PolyP in prokaryotes and unicellular eukaryotes is typically hundreds of phosphate units long, while polyP in dense granules of human platelets is ∼75 phosphates long. PolyP is secreted upon platelet activation, and we recently reported that it is a potent hemostatic regulator, acting at multiple points in the clotting cascade: PolyP triggers the contact pathway, accelerates factor V activation, and abrogates the anticoagulant function of tissue factor pathway inhibitor (TFPI). Our previous experiments utilized relatively heterodisperse polyP preparations. We have now isolated polyP fractions of defined polymer lengths and here report the size dependence of the various procoagulant effects of polyP. Methods: PolyP preparations were carefully size-fractionated by gel electrophoresis (Clark and Wood, Anal. Biochem. 1987, 161:280–290). Clotting assays were performed using pooled normal plasma with or without added recombinant TFPI or 40–50 μM polyP. Clotting was initiated by tissue factor (TF), factor Xa (FXa), or CaCl2 alone (contact pathway). Results: Of the polyP procoagulant activities tested, triggering the contact pathway required the longest polymers: We observed weak triggering of the contact pathway with ∼75mers and increasing procoagulant activity as polymer lengths increased, with maximal contact pathway activation requiring 450mers or longer. On the other hand, the downstream procoagulant effects of polyP required significantly shorter polyP polymers. (When clotting is triggered by either TF or FXa, further shortening of clotting times by polyP is attributed to accelerated factor V activation.) Minimum polymer lengths required to shorten TF or FXa clot times were ∼37mers, with maximal activity requiring 75mers or longer. Finally, the ability of polyP to abrogate TFPI anticoagulant function required the shortest minimum polymer lengths: Detectable anti-TFPI activity was observed with 11mers, with maximal activity requiring 49mers or longer. Conclusions: PolyP exhibited different minimum length requirements for its various procoagulant effects, consistent with the idea that polyP interacts with different proteins at various points in the clotting cascade. Contact pathway activation required very long polymers that were similar in size to those in infectious microorganisms. Therefore, triggering of the contact pathway by polyP may contribute to procoagulant/inflammatory responses to infection. In contrast, acceleration of factor V activation by polyP was maximal with polymers of the size released from human platelets. Even shorter polyP polymers abrogated TFPI function, suggesting that at least some of polyP’s anti-TFPI effect may be mediated by mechanisms other than (or in addition to) its ability to accelerate factor V activation.
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Cao, Jun Hui, Wen Zhi Fu, Ming Zhe Li, Chun Guo Liu, and He Li Peng. "Research of Polycarbonate Sheet Processing Based on Multi-Point Forming." Applied Mechanics and Materials 161 (March 2012): 77–81. http://dx.doi.org/10.4028/www.scientific.net/amm.161.77.
Abstract:
Although multi-point forming (MPF) is an advanced processing technique and has been investigated comprehensively as a metal working operation, there are few papers published to deal with MPF of polymers. The present paper reviews the features of MPF and evaluates the possibility of producing polymer components by means of MPF. The experimental research work makes use of PC sheets with a thickness of 3.82 mm. Numerical simulations were performed with the software ABAQUS, then spherical and saddle-shaped components were manufactured by MPF. The geometrical deviations between shaped components and their original CAD/CAM models were obtained to investigate the forming accuracy. The results confirm that MPF of PC sheet has potential for the manufacture of complex components.
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Sharifpanah, Fatemeh, Matthias Reinhardt, Johanna Schönleben, Claudia Meyer, Madeleine Richter, Matthias Schnabelrauch, Claudia Rode, et al. "Embryonic Stem Cells for Tissue Biocompatibility, Angiogenesis, and Inflammation Testing." Cells Tissues Organs 204, no. 1 (2017): 1–12. http://dx.doi.org/10.1159/000471794.
Abstract:
Aim: To introduce embryoid bodies derived from mouse embryonic stem (ES) cells, which differentiate blood vessel-like structures and leukocytes, as a novel in vitro model system for biocompatibility, inflammation, and angiogenesis studies. Methodology/Results: Punched spherical discs of bioabsorbable polymers (ε-caprolactone and L-lactide in different compositions) with a diameter of 2 mm and a thickness of 0.2 mm were inoculated with embryoid bodies for cocultivation. As reference material for biocompatible, nonbioabsorbable, and bioincompatible materials, polymer punched discs of petriPERM (PP) membrane (polytetrafluoroethylene) as well as polyvinylchloride (PVC) were used. Tissue outgrowth on the polymer discs decreased and cell toxicity increased upon confrontation on bioabsorbable biomaterials and PVC. Bioabsorbable polymers as well as PVC decreased the branching points and total tube length of CD31-positive vascular structures in embryoid bodies. With the exception of PP, all applied materials increased the differentiation of CD68-positive macrophages and the generation of reactive oxygen species, which is indicative of proinflammatory processes upon contact of tissue with biomaterials. Consequently, cocultivation with polymers increased secretion of the cytokines interleukin-6, monocyte chemotactic protein-1, and tumor necrosis factor-α. Conclusion: Three-dimensional tissues cultivated from ES cells are well-suited for testing the biocompatibility, the vascular response, and the inflammatory reaction towards bioabsorbable and nonbioabsorbable polymers.
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Contreras, L., L. M. Melgoza, A. Aguilar-de-Leyva, and I. Caraballo. "Collaboration between HPMC and NaCMC in order to Reach the Polymer Critical Point in Theophylline Hydrophilic Matrices." Scientific World Journal 2012 (2012): 1–8. http://dx.doi.org/10.1100/2012/171292.
Abstract:
Percolation theory has been applied in order to study the existence of critical points as well as the possibility to find a “combined percolation threshold” for ternary hydrophilic matrices prepared with HPMC, NaCMC, and theophylline. For this purpose, different batches of ternary as well as binary hydrophilic matrices have been prepared. Critical points have been found for binary hydrophilic matrices between 21.5 and 31.3% (v/v) of HPMC and between 39 and 54% (v/v) of NaCMC, respectively. In a previous work carried out with the same polymers but a much more soluble drug (KCl), it was demonstrated the existence of a partial collaboration between the polymers in order to establish the gel layer. In this work, it has been observed for the first time the need of a minimum concentration of one of the matrix-forming polymer (between 10 and 20% v/v, approximately) for establishing an effective collaboration.
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Magonov, Sergei, Marko Surtchev, John Alexander, Ivan Malovichko, and Sergey Belikov. "Mapping of Nanoscale Mechanical Properties of Polymers in Quasi-static and Oscillatory Atomic Force Microscopy Modes." MRS Advances 1, no. 40 (2016): 2763–68. http://dx.doi.org/10.1557/adv.2016.539.
Abstract:
ABSTRACTRecent advances in studies of local mechanical properties of polymers with different atomic force microscopy techniques (contact, Hybrid and amplitude modulation modes) are described in interplay between experiment and theory. Analysis of force curves and time dependencies of probe response to sample compliance, which were recorded on a number of polymer materials at various temperatures, leads to quantitative mapping of specific mechanical properties (elastic modulus, work of adhesion, etc). High spatial resolution of elastic modulus mapping (10-20 nm) is illustrated in measurements of lamellar structures of several polymers. Challenges of examination of viscoelastic properties are pointed out and a possible solution is presented.
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Kjalarsdóttir, Lilja, Arna Dýrfjörd, Atli Dagbjartsson, Elín H. Laxdal, Gissur Örlygsson, Jóhannes Gíslason, Jón M. Einarsson, Chuen-How Ng, and Halldór Jónsson. "Bone remodeling effect of a chitosan and calcium phosphate-based composite." Regenerative Biomaterials 6, no. 4 (March 18, 2019): 241–47. http://dx.doi.org/10.1093/rb/rbz009.
Abstract:
Abstract Chitosan is a biocompatible polymer that has been widely studied for tissue engineering purposes. The aim of this research was to assess bone regenerative properties of an injectable chitosan and calcium phosphate-based composite and identify optimal degree of deacetylation (%DDA) of the chitosan polymer. Drill holes were generated on the left side of a mandible in Sprague-Dawley rats, and the hole was either left empty or filled with the implant. The animals were sacrificed at several time points after surgery (7–22 days) and bone was investigated using micro-CT and histology. No significant new bone formation was observed in the implants themselves at any time points. However, substantial new bone formation was observed in the rat mandible further away from the drill hole. Morphological changes indicating bone formation were found in specimens explanted on Day 7 in animals that received implant. Similar bone formation pattern was seen in control animals with an empty drill hole at later time points but not to the same extent. A second experiment was performed to examine if the %DDA of the chitosan polymer influenced the bone remodeling response. The results suggest that chitosan polymers with %DDA between 50 and 70% enhance the natural bone remodeling mechanism.
39
Tarasova, N. P., E. G. Krivoborodov, and Y. O. Mezhuev. "CURRENT TRENDS IN THE SYNTHESIS OF INORGANIC AND ORGANOELEMENT PHOSPHORUS- AND SULFUR-CONTAINING POLYMERS. A REVIEW." Доклады Российской академии наук. Химия, науки о материалах 512, no. 1 (September 1, 2023): 5–20. http://dx.doi.org/10.31857/s2686953523600022.
Abstract:
The analysis of the literature data on the set of reactions for the production of macromolecules with a high content of phosphorus and sulfur is carried out, and the main approaches allowing to involve these elements in the composition of polymers and polymer materials, considering the fundamental principles of green chemistry, are considered. The methods leading to the formation of functional polymers under mild conditions with minimal energy consumption from external sources necessary for the synthesis, which can become new growth points of green industrial technologies, are considered. Particular attention is paid to the issues of synthesis of polyphosphazenes and polyphosphoesters for biomedical purposes, as well as the inverse vulcanization reaction with the formation of polymers that are used in sorption wastewater treatment, the creation of current sources and IR optics.
40
Qiu, Liangwei, Xiaoyang Chen, and Fakai Dong. "Effects of polymers concentration on EHL film-forming in point contacts." Industrial Lubrication and Tribology 73, no. 3 (February 17, 2021): 436–42. http://dx.doi.org/10.1108/ilt-07-2020-0263.
Abstract:
Purpose This paper aims to experimentally investigate the film-forming capability of base oils containing poly-methacrylate (PMA) and poly-isobutene (PIB), in a point contact under pure rolling. Design/methodology/approach By using the relative light intensity method, the film thickness is calculated from the interferometer images which are captured by multiple-contact optical elastohydrodynamic lubricated test rig. Findings The test results reveal that polymers, both PMA and PIB, have a significant contribution to the film-forming capability of base oils and the film thickness increases with concentration. The forming-film capabilities for PMA and PIB in base oils are similar at low concentration, while PIB gives a higher film thickness than PMA at high concentration. Shear-thinning phenomenon are observed in all polymer-based oils. Originality/value The polymer usually as an additive is added into the low viscosity base oils to improve the properties of lubricant oil. This paper reports the lubricated properties of PMA and PIB with different concentrations in base oils and to evaluate their functional mechanism in a point contact. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0263/
41
Cuthbertson, Leslie, Iain L. Mainprize, James H. Naismith, and Chris Whitfield. "Pivotal Roles of the Outer Membrane Polysaccharide Export and Polysaccharide Copolymerase Protein Families in Export of Extracellular Polysaccharides in Gram-Negative Bacteria." Microbiology and Molecular Biology Reviews 73, no. 1 (March 2009): 155–77. http://dx.doi.org/10.1128/mmbr.00024-08.
Abstract:
SUMMARY Many bacteria export extracellular polysaccharides (EPS) and capsular polysaccharides (CPS). These polymers exhibit remarkably diverse structures and play important roles in the biology of free-living, commensal, and pathogenic bacteria. EPS and CPS production represents a major challenge because these high-molecular-weight hydrophilic polymers must be assembled and exported in a process spanning the envelope, without compromising the essential barrier properties of the envelope. Emerging evidence points to the existence of molecular scaffolds that perform these critical polymer-trafficking functions. Two major pathways with different polymer biosynthesis strategies are involved in the assembly of most EPS/CPS: the Wzy-dependent and ATP-binding cassette (ABC) transporter-dependent pathways. They converge in an outer membrane export step mediated by a member of the outer membrane auxiliary (OMA) protein family. OMA proteins form outer membrane efflux channels for the polymers, and here we propose the revised name outer membrane polysaccharide export (OPX) proteins. Proteins in the polysaccharide copolymerase (PCP) family have been implicated in several aspects of polymer biogenesis, but there is unequivocal evidence for some systems that PCP and OPX proteins interact to form a trans-envelope scaffold for polymer export. Understanding of the precise functions of the OPX and PCP proteins has been advanced by recent findings from biochemistry and structural biology approaches and by parallel studies of other macromolecular trafficking events. Phylogenetic analyses reported here also contribute important new insight into the distribution, structural relationships, and function of the OPX and PCP proteins. This review is intended as an update on progress in this important area of microbial cell biology.
42
Toma, Flavia Roxana, Lavinia Cristina Moleriu, and Liliana Porojan. "Micro-CT Marginal and Internal Fit Evaluation of CAD/CAM High-Performance Polymer Onlay Restorations." Polymers 15, no. 7 (March 30, 2023): 1715. http://dx.doi.org/10.3390/polym15071715.
Abstract:
(1) Background: The use of high-performance polymers for fixed restorations requires additional studies regarding their adaptability and processing with CAD/CAM technology. This in vitro study aims to assess the marginal and internal fit of PEEK and PEKK materials using microcomputed tomography. (2) Methods: Twenty-four (n = 8) MOD onlays made of PEKK (Pekkton ivory), unmodified PEEK (Juvora medical), and modified PEEK (BioHPP) were investigated. A typodont mandibular left first molar was scanned to achieve 24 resin, 3D printed abutment teeth. The onlays were fabricated with a five-axis milling machine, and after cementation of the specimens, the marginal (MG) and internal gaps (IG) were evaluated at twelve points in the mesio-distal section and thirteen points in the bucco-lingual section using microcomputed tomography. For statistical data analysis, Wilcoxon signed-rank/paired Student t-Test, Mann–Whitney/unpaired Student t-Test, and one-way ANOVA test were applied. (3) Results: Significant differences (p < 0.05; α = 0.05) were reported between the MG and IG for each material for all three polymers and also among two materials in terms of the MG and IG (except Juvora-BioHPP). The highest IG values were recorded in angular areas (axio-gingival line angle) in the mesio-distal section for all the polymers. (4) Conclusions: For all the materials, MG < IG. The type of polymer influenced the adaptability; the lowest marginal and internal gap mean values were recorded for BioHPP. The analyzed polymer used for onlays are clinically acceptable in terms of adaptability.
43
Wang, Xudong, Binshan Ju, Yi Jin, and Yapeng Tian. "Iso-Permeability Point Trail Method to Determine the Relative Permeability Curve for a New Amphiphilic Polymer Flooding." Energies 16, no. 21 (October 31, 2023): 7362. http://dx.doi.org/10.3390/en16217362.
Abstract:
Amphiphilic-polymer flooding, which can increase water viscosity, decrease oil viscosity, and improve oil displacement efficiency, is a promising oil exploitation method for heavy oil. Due to oil–water emulsification, shear-thinning, and changes in oil viscosity when determining the relative permeability data of new amphiphilic polymers, the conventional J.B.N. method is not accurate. This paper presents a new method called the iso-permeability point trial method to determine the relative permeability curve by combining the J.B.N. method, the Corey model, and the relationship between water saturation and the relative permeability ratio. To avoid using polymer viscosity, a mathematical equation was derived based on the characteristics of the relative permeability curve. The results indicate that the new method is feasible and the obtained curve is more reasonable and smooth. The influence of concentration, permeability, and oil viscosity on amphiphilic-polymer displacement relative permeability was also analyzed, demonstrating that under the same water saturation, the water relative permeability is lower than that of water flooding but the oil relative permeability is bigger, which manifests as the iso-permeability point moves to the right and results in a lower residual oil saturation. In addition, the aforementioned trends are more obvious when the amphiphilic-polymer concentration is high, formation permeability is low, and oil viscosity is low.
44
Furukawa, Junju. "Transition points of polymers." Journal of Applied Polymer Science 57, no. 9 (August 29, 1995): 1085–93. http://dx.doi.org/10.1002/app.1995.070570907.
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Cheng, Xiaoxiao, Tengfei Miao, Yilin Qian, Zhengbiao Zhang, Wei Zhang, and Xiulin Zhu. "Supramolecular Chirality in Azobenzene-Containing Polymer System: Traditional Postpolymerization Self-Assembly Versus In Situ Supramolecular Self-Assembly Strategy." International Journal of Molecular Sciences 21, no. 17 (August 27, 2020): 6186. http://dx.doi.org/10.3390/ijms21176186.
Abstract:
Recently, the design of novel supramolecular chiral materials has received a great deal of attention due to rapid developments in the fields of supramolecular chemistry and molecular self-assembly. Supramolecular chirality has been widely introduced to polymers containing photoresponsive azobenzene groups. On the one hand, supramolecular chiral structures of azobenzene-containing polymers (Azo-polymers) can be produced by nonsymmetric arrangement of Azo units through noncovalent interactions. On the other hand, the reversibility of the photoisomerization also allows for the control of the supramolecular organization of the Azo moieties within polymer structures. The construction of supramolecular chirality in Azo-polymeric self-assembled system is highly important for further developments in this field from both academic and practical points of view. The postpolymerization self-assembly strategy is one of the traditional strategies for mainly constructing supramolecular chirality in Azo-polymers. The in situ supramolecular self-assembly mediated by polymerization-induced self-assembly (PISA) is a facile one-pot approach for the construction of well-defined supramolecular chirality during polymerization process. In this review, we focus on a discussion of supramolecular chirality of Azo-polymer systems constructed by traditional postpolymerization self-assembly and PISA-mediated in situ supramolecular self-assembly. Furthermore, we will also summarize the basic concepts, seminal studies, recent trends, and perspectives in the constructions and applications of supramolecular chirality based on Azo-polymers with the hope to advance the development of supramolecular chirality in chemistry.
46
Rothwell, S. W., W. A. Grasser, and D. B. Murphy. "End-to-end annealing of microtubules in vitro." Journal of Cell Biology 102, no. 2 (February 1, 1986): 619–27. http://dx.doi.org/10.1083/jcb.102.2.619.
Abstract:
Mixtures of pre-formed microtubules, polymerized from chicken erythrocyte and brain tubulin, rapidly anneal end-to-end in vitro in standard microtubule assembly buffer. The erythrocyte tubulin segments in annealed heteropolymers can be distinguished by an immunoelectron microscopic assay that uses an antibody specific for chicken erythrocyte beta-tubulin. An annealing process is consistent with the following observations: (a) Microtubule number decreases while the polymer mass remains constant. (b) As the total number of microtubules declines, the number of heteropolymers, and the number of segments contained in each heteropolymer, increases. (c) The size of the segments determined after annealing and antibody labeling is the same as the original microtubule polymers. (d) Points of discontinuity in the annealing heteropolymers can be observed directly by electron microscopy, and correspond to type-specific polymer domains. The junctions probably represent initial contact points during the annealing process. Microtubule annealing occurs rapidly in vitro and may be significant for determining properties of microtubule dynamics in vivo.
47
Xu, Xin, and Ying Jiang. "Applications of worm-like chain model in polymer physics." International Journal of Modern Physics B 32, no. 18 (July 15, 2018): 1840006. http://dx.doi.org/10.1142/s0217979218400064.
Abstract:
Saito, Takahashi and Yunoki developed the continuous version of worm-like chain (WLC) model that is very suitable for description of the polymer conformational properties affected by chain rigidity. By adjusting persistence length directly, the WLC model can depict the extensive range of chain conformations from flexible chains to rigid chains. It is widely accepted that more physical properties of real polymer can be obtained by utilizing coarse-grained model than Gaussian chain (GSC). This paper reviews the applications of the WLC model in the framework based on self-consistent field theory, which is an efficient method of theoretical exploration of phase separation in polymer system. It is noticed that the development of numerical schemes is in favor of solving modified diffusion equation that adjusts the probability distribution of polymers. In addition, we conclude the recent applications of the self-consistent field theory based on the WLC model as the following three points: phase transitions of liquid crystal polymer; the influences of surface curvature on polymer system that involves the chain orientation effects; self-assembly of worm-like block copolymer. These researches have been out of the range of the self-consistent field theory based on GSC model that has been used in a large number of theoretical studies. Finally, we present ideas of theoretical development in field theory simulations based on the WLC model in the future. It is universally acknowledged that chain rigidity is a key factor that influences the properties of structural stabilities in the meso-scale in articles. Theoretical researches determine the key physical mechanisms that play crucial roles in many experimental systems with attractively promising applications in practice, for systems such as liquid crystalline polymers and organic solar cell based on the conjugated polymers.
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Lin, Guo Min, Fang Yuan, and Yan Hua Li. "Current Situation and Latest Development of Intelligent Materials." Advanced Materials Research 989-994 (July 2014): 288–91. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.288.
Abstract:
The background and design idea of the intelligent materials is introduced. Three elements of intelligent materials are given. Then based on classifying of intelligent materials, the features and applications of intelligent materials are researched.Principle and the latest applications of typical intelligent materials such as optical fiber, shape memory alloys, shape memory polymers, piezoelectric, magnetostrictive materials, fluid material and polymer colloid are analyzed simplely. The research difficulties and the future research focuses of intelligent material are pointed out.
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Selyaev, Vladimir, Tatyana Nizina, Dmitry Nizin, and Nadezhda Kanaeva. "ANALYSIS OF THE MOISTURE CONTENT EFFECT ON THE SPECIFIC INDEX AND DAMAGE ACCUMULATION KINETICS IN THE STRUCTURE OF POLYMERIC MATERIALS DURING NATURAL CLIMATIC AGING." International Journal for Computational Civil and Structural Engineering 18, no. 1 (March 31, 2022): 99–108. http://dx.doi.org/10.22337/2587-9618-2022-18-1-99-108.
Abstract:
We present the results analyzing the climatic resistance of epoxy polymers obtained on the basis of a modified Etal-247 resin cured by Etal-45M under the effect of natural climatic factors in a temperate continental climate. The kinetics of damage accumulation in the structure of polymer samples under tensile loads was studied on the basis of the results obtained using the author's method. The essence of the technique was to determine the coordinates of the “critical” points of deformation curves based on the time series fractal analysis methods, recorded with a high readings frequency (0.01 s). To estimate the level of accumulated failures leading to the de-struction of samples under tensile loads, we used a parameter defined as the ratio of the number of points with a fractality index less than 0.5 to the total number of points on deformation curves (until reaching the level of “critical” tensile stresses). Time intervals of 0.16 seconds were studied with analyzed area shifted with a step of 0.01 sec. A specific index is proposed that characterizes the accumulated number of damages in the polymer sample structure per unit of its strength. Its achievement leads to the destruction of the composite under study. We have determined the moisture state effect and climatic aging duration on the damage accumulation kinetics in the polymer sample structure under tensile loads.
50
Ratner, Mark A., and D. F. Shriver. "Polymer Ionics." MRS Bulletin 14, no. 9 (September 1989): 39–51. http://dx.doi.org/10.1557/s0883769400061728.
Abstract:
The preparation, utilization, and understanding of high polymers represents one of the great triumphs of chemistry and materials science in the 20th century. Synthetic polymers have traditionally been used as structural materials and electrical insulators. Biopolymers often exhibit interesting electrical response phenomena. A recent article in the MRS BULLETIN, for example, discussed piezoelectric properties of both synthetic and biopolymer systems. The newer, synthetic electroactive polymeric materials, however, represent one of the most exciting current areas of polymer materials science.Many synthetic ionic polymer materials are known; perhaps the first were the polyelectrolytes and crosslinked ion exchange materials. These are materials whose backbone contains charges of one sign, balanced by small counter ions of the opposite sign. Such polyelectrolytes have found very important applications in analytical chemistry, water purification, and chemical processing.Complexes, in which salts are dissolved in neutral polymer hosts, have until recently received less attention. The area of polymer/salt complexes became extremely active following the work of P.V. Wright, who first clearly showed that polyethylene oxide (PEO) is an excellent polymer host for a number of salts, and that the resulting solid polymer/salt complexes are electrical conductors. M. Armand broadened the investigation of electrical properties of polymer/salt complexes and pointed out that these materials might be useful in electrochemical devices, especially batteries.This article will discuss the formation, properties, behavior, and applications of polymer electrolytes and mixed conductors—that is, polymeric materials in which charge is transported either by ions or by ionic and electronic charge motion. Our concentration will be on solvent-free materials—materials in which no small molecule solvents are present. There is substantial interest, and substantial progress, in the area of solvent-swollen polymer electrolytes.