Polymer Configurations Research Articles

Pushover Analysis of a Reinforced Cement Concrete (RCC) Structure Incorporating Fibre-Reinforced Polymers to Address Vertical Irregularities

India has had four of the world's most destructive earthquakes in the past ten years, and our country is often rocked by earthquakes of low to moderate intensity. Since many buildings were severely damaged or collapsed, it has sparked debate whether framed constructions are sufficiently sturdy to withstand significant vibrations. As a result, the strength or ability of existing reinforced concrete structures to withstand seismic loads can be evaluated. The performance level of earthquake-prone buildings is evaluated using a performance-based design. One seismic technique for assessing a building's performance level is push-over analysis. It is possible to determine whether damage occurs at the member or structure level using pushover analysis. The study employs pushover analysis by Applied Technology Council (ATC) – 4), a seismic assessment technique, to evaluate the ability of 20-story buildings in seismic Zone III (with hard soil characteristics) to resist earthquake-induced forces. The primary objective was to assess the performance of structures reinforced with different fiber-reinforced polymer (FRP) materials, including aramid, glass, and carbon fibers, known for their high flexibility and strength in seismically active regions. To determine the best fiber-reinforced polymer configuration, the study considers the following parameters: pushover curve, target displacement, story shear, time period, maximum story displacement, and story drift based on pushover analysis independently. Through the pushover analysis method, the research discovers that FRP wrapping can significantly improve the seismic performance of reinforced concrete buildings. The findings aim to improve building design practices by recommending fiber-reinforced polymer configurations for better earthquake resistance, ensuring that future constructions are better equipped to handle seismic activity.

Optimization of Carbon Fiber-Reinforced Polymer (CFRP) Configuration for Enhanced Flexural Performance in Strengthened Concrete Beams

Optimization of Carbon Fiber-Reinforced Polymer (CFRP) Configuration for Enhanced Flexural Performance in Strengthened Concrete Beams

Polymeric Lithium Battery using Membrane Electrode Assembly

Alternative configuration lithium cell exploits electrode and polymer electrolyte cast all‐in‐one to form a membrane electrode assembly (MEA), in analogy to fuel cell technology. The electrolyte is based on polyethylene oxide (PEO), lithium bis‐trifluoro sulfonyl imide (LiTFSI) conducting salt, LiNO3 sacrificial film‐forming agent to stabilize the lithium metal, and fumed silica (SiO2) to increase the polymer amorphous degree. The membrane has conductivity ranging from ~5×10−4 S cm‐1 at 90 °C to 1×10−4 S cm‐1 at 50 °C, lithium transference number of ~0.4, and relevant interphase stability. The MEA including LiFePO4 (LFP) cathode is cycled in polymer lithium cells operating at 3.4 V and 70 °C, with specific capacity of ~155 mAh g‐1 (1C = 170 mA gLFP‐1) for over 100 cycles, without signs of decay or dendrite formation. The cell exploiting the MEA shows enhanced electrochemical performance as compared with the one using simple polymeric membrane stacked between cathode and anode. Furthermore, the MEA reveals the key advantage of possible scalability and applicability in roll‐to‐roll systems for achieving high‐energy lithium metal battery, as demonstrated by pouch‐cell application. These data may trigger new interest on this challenging battery exploiting the polymer configuration for achieving environmentally/economically sustainable, and safe energy storage.

A Gram-Charlier Analysis of Scattering to Describe Nonideal Polymer Conformations.

Theories of interpreting polymer physics and rheology at the molecular level from experiments, including small-angle scattering, typically rely on the assumption that polymer chains possess a Gaussian configuration distribution. This assumption frequently fails to describe features of real polymer molecules both at equilibrium (when polymers have nonlinear topology or heterogeneous chemistry) and out of equilibrium (when they are subjected to nonlinear deformations). To better describe non-Gaussian polymer conformation distributions, we propose a moments analysis based on the Gram-Charlier expansion as a natural framework for describing structure and scattering from non-Gaussian polymers. The expansion describes the conformation distribution in terms of cumulants (equivalent to moments of the distribution) of the underlying segment density distribution function, providing low-dimensional descriptors that can be inferred directly from measured scattering in a way that is agnostic to a polymer's topology, chemistry, or state of deformation. We use this framework to show that cumulants can be used to "fingerprint" non-Gaussian conformation distributions of polymers either at equilibrium (applied to sequence-defined heteropolymers) or out of equilibrium (applied to polymers experiencing nonlinear deformation due to flow). We anticipate that this new analysis method will provide a general framework for examining nonideal polymer configurations and the properties that arise from them.

Self-Assembly of Three-Dimensional Hyperbranched Magnetic Composites and Application in High-Turbidity Water Treatment.

In order to improve dispersibility, polymerization characteristics, chemical stability, and magnetic flocculation performance, magnetic Fe3O4 is often assembled with multifarious polymers to realize a functionalization process. Herein, a typical three-dimensional configuration of hyperbranched amino acid polymer (HAAP) was employed to assemble it with Fe3O4, in which we obtained three-dimensional hyperbranched magnetic amino acid composites (Fe3O4@HAAP). The characterization of the Fe3O4@HAAP composites was analyzed, for instance, their size, morphology, structure, configuration, chemical composition, charged characteristics, and magnetic properties. The magnetic flocculation of kaolin suspensions was conducted under different Fe3O4@HAAP dosages, pHs, and kaolin concentrations. The embedded assembly of HAAP with Fe3O4 was constructed by the N-O bond according to an X-ray photoelectron energy spectrum (XPS) analysis. The characteristic peaks of -OH (3420 cm-1), C=O (1728 cm-1), Fe-O (563 cm-1), and N-H (1622 cm-1) were observed in the Fourier transform infrared spectrometer (FTIR) spectra of Fe3O4@HAAP successfully. In a field emission scanning electron microscope (FE-SEM) observation, Fe3O4@HAAP exhibited a lotus-leaf-like morphological structure. A vibrating sample magnetometer (VSM) showed that Fe3O4@HAAP had a relatively low magnetization (Ms) and magnetic induction (Mr); nevertheless, the ferromagnetic Fe3O4@HAAP could also quickly respond to an external magnetic field. The isoelectric point of Fe3O4@HAAP was at 8.5. Fe3O4@HAAP could not only achieve a 98.5% removal efficiency of kaolin suspensions, but could also overcome the obstacles induced by high-concentration suspensions (4500 NTU), high pHs, and low fields. The results showed that the magnetic flocculation of kaolin with Fe3O4@HAAP was a rapid process with a 91.96% removal efficiency at 0.25 h. In an interaction energy analysis, both the UDLVO and UEDLVO showed electrostatic repulsion between the kaolin particles in the condition of a flocculation distance of <30 nm, and this changed to electrostatic attraction when the separation distance was >30 nm. As Fe3O4@ HAAP was employed, kaolin particles could cross the energy barrier more easily; thus, the fine flocs and particles were destabilized and aggregated further. Rapid magnetic separation was realized under the action of an external magnetic field.

Mean-Field Ring Polymer Rates Using a Population Dividing Surface.

Mean-field ring polymer molecular dynamics offers a computationally efficient method for the simulation of reaction rates in multilevel systems. Previous work has established that, to model a nonadiabatic state-to-state reaction accurately, it is necessary to ensure reactive trajectories form kinked ring polymer configurations at the dividing surface. Building on this idea, we introduce a population difference coordinate and a reactive flux expression modified to only include contributions from kinked configurations. We test the accuracy of the resulting mean-field rate theory on a series of linear vibronic coupling model systems. We demonstrate that this new kMF-RP rate approach is efficient to implement and quantitatively accurate for models over a wide range of driving forces, coupling strengths, and temperatures.

Aqueous size exclusion chromatography applied to polymer analysis: experimental conditions and molecular weight calibration curves

Aqueous mode size exclusion chromatography (SEC) was employed for the analysis and construction of molecular weight (MW) calibration curves of three water-soluble polymers, namely, polyethylene glycol, polyethylene oxide, and polyacrylic acid sodium salt. Several calibration curves were obtained, varying chromatographic conditions such as columns arrangement, ionic strength, temperature and pH, in addition trends in polymeric chromatographic behavior were examined. The variation in SEC distribution coefficients at different temperatures was found to be below 10 %, indicating that the studied polymers follow an ideal SEC mechanism under the tested conditions. Thus, differences in chromatographic behavior were ascribed to changes in polymer configuration induced by media and/or temperature. These variations in morphology were consistent with the observed SEC behavior.Regarding MW calibration, polynomial regression models ranging from first to fifth order were applied, and the most adequate ones were selected based on their fit and prediction capabilities. Third order polynomials were the preferred models for polyethylene glycol and polyacrylic acid sodium salt, independently of chromatographic conditions. Meanwhile for polyethylene oxide, either third or fifth-order polynomial models were optimal depending on the chromatographic conditions. All the selected regression models presented coefficients of multiple determination (R2) above 0.990, while achieving relative errors of prediction (REP%) in MW ranging from 0.3 to 4 % for cross-validation.

Physics-Informed Deep Learning Approach for Reintroducing Atomic Detail in Coarse-Grained Configurations of Multiple Poly(lactic acid) Stereoisomers.

Multiscale modeling of complex molecular systems, such as macromolecules, encompasses methods that combine information from fine and coarse representations of molecules to capture material properties over a wide range of spatiotemporal scales. Being able to exchange information between different levels of resolution is essential for the effective transfer of this information. The inverse problem of reintroducing atomistic degrees of freedom in coarse-grained (CG) molecular configurations is particularly challenging as, from a mathematical point of view, it is an ill-posed problem; the forward mapping from the atomistic to the CG description is typically defined via a deterministic operator ("one-to-one" problem), whereas the reversed mapping from the CG to the atomistic model refers to creating one representative configuration out of many possible ones ("one-to-many" problem). Most of the backmapping methods proposed so far balance accuracy, efficiency, and general applicability. This is particularly important for macromolecular systems with different types of isomers, i.e., molecules that have the same molecular formula and sequence of bonded atoms (constitution) but differ in the three-dimensional configurations of their atoms in space. Here, we introduce a versatile deep learning approach for backmapping multicomponent CG macromolecules with chiral centers, trained to learn structural correlations between polymer configurations at the atomistic level and their corresponding CG descriptions. This method is intended to be simple and flexible while presenting a generic solution for resolution transformation. In addition, the method is aimed to respect the structural features of the molecule, such as local packing, capturing therefore the physical properties of the material. As an illustrative example, we apply the model on linear poly(lactic acid) (PLA) in melt, which is one of the most popular biodegradable polymers. The framework is tested on a number of model systems starting from homopolymer stereoisomers of PLA to copolymers with randomly placed chiral centers. The results demonstrate the efficiency and efficacy of the new approach.

Polymer configuration conversion mechanism in dynamically stable interface of silicon anodes

During the lithiation process, –CN– groups in the PHATN coordinate with Li+ to form –C–N–Li– bonds on PHATN molecule layer. The dynamic volume change of the PHATN molecule provides excellent protection against structural collapse.

Single-chain simulation of Ising density functional theory for weak polyelectrolytes.

Conventional theories of weak polyelectrolytes are either computationally prohibitive to account for the multidimensional inhomogeneity of polymer ionization in a liquid environment or oversimplistic in describing the coupling effects of ion-explicit electrostatic interactions and long-range intrachain correlations. To bridge this gap, we implement the Ising density functional theory (iDFT) for ionizable polymer systems using the single-chain-in-mean-field algorithm. The single-chain-in-iDFT (sc-iDFT) shows significant improvements over conventional mean-field methods in describing segment-level dissociation equilibrium, specific ion effects, and long-range intrachain correlations. With an explicit consideration of the fluctuations of polymer configurations and the position-dependent ionization of individual polymer segments, sc-iDFT provides a faithful description of the structure and thermodynamic properties of inhomogeneous weak polyelectrolyte systems across multiple length scales.

Nonlinear finite element modeling of reinforced concrete beam–column joints retrofitted using various plates configurations of carbon fiber-reinforced polymers

Nonlinear finite element modeling of reinforced concrete beam–column joints retrofitted using various plates configurations of carbon fiber-reinforced polymers

Molecular dynamics simulations of several linear homopolymers: Assessment and comparison of shock properties

Understanding the behavior of polymers under shock loading is essential for their applications in car equipment, aircraft, space structure and plastic bonded explosives. Despite much effort, both experimentally and numerically over the last twenty years, there are specificities of the shock behavior of polymers that are still unclear. These include the relation of the shocked state to the dynamic glass transition and the deviation of the Hugoniot locus from the usual linear relation us=c+Sup, with us the shock velocity, c, the bulk sound velocity, up the particle velocity and S an empirical fitting parameter. To address these questions this work studies direct shock simulations in molecular dynamics (MD) of three different polymers, cis-1,4-polybutadiene, polystyrene and phenoxy resin. After thoroughly assessing that the polymer configurations created in this work are correct with respect to mass density, structure factor, chain dimensions and Hugoniot locus, this work focuses on two aspects of the behavior under shock loading. (i) The deviation of the Hugoniot locus from the linear relation us=c+Sup is related to a change in the relative contribution to the shock energy of the bonding and non-bonding potential energies as the shock strength increases. (ii) The shear stress relaxations behind the shock front are compared for the three polymers. It is found that the polymers with the highest glass transition temperature have the most slowly relaxing shear stress behind the shock front.

Dextran of Diverse Molecular-Configurations Used as a Blood-Plasma Substitute, Drug-Delivery Vehicle and Food Additive Biosynthesized by Leuconostoc, Lactobacillus and Weissella

Dextran, a microbial metabolite of diverse molecular configurations, can be biosynthesized employing selected strains of characterized species of bacteria. Dextran molecules are secreted as an extracellular polysaccharide in the culture medium of the bacterial fermentation system. This microbially produced polymer of glucose possesses multi-faceted characteristics such as its solubility in different solvents and formation of dextran solutions of needed viscosity. Several preparations can be formulated for the desired thermal and rheological properties. Due to such multifunctional characteristics, dextran with different structural specifications is a desired polysaccharide for clinical, pharmaceutical, and food industry commercial applications. Dextran and its derivative products with various molecular weights, in a range of high and low, have established their uses in drug delivery and in analytical devices using columns packed with polysaccharide gel. Therefore, being a neutral raw material, the resourcefulness of dextran preparations of different molecular weights and linkages in their polymer configuration is important. For this purpose, several studies have been performed to produce this commercially important polysaccharide under optimized bacterial cultivation processes. This article aims to overview recently published research reports on some significant applications of dextran in the pharmaceutical and food industries. Studies conducted under optimized conditions in fermentation processes for the biosynthesis of dextran of diverse molecular configurations, which are responsible for its multifunctional properties, have been summarized. Concise information has been presented in three separate tables for each group of specific bacterial species employed to obtain this extracellular microbial polysaccharide.

Designing Multimodal ON-OFF Nanoswitches of DNA-Functionalized Nanoparticles by Stimuli-Responsive Polymers.

It is a challenging task to realize highly reversible ON-OFF nanoswitches over a wide range of temperatures, which emerge as a versatile toolbox for use in nanobiotechnology. Herein, nanoparticles (NPs) bifunctionalized by DNA strands and stimuli-responsive polymers are proposed to construct multimodal ON-OFF nanoswitches by the coarse-grained model. The successful achievement of multimodal ON-OFF nanoswitches for bifunctionalized NPs at lower temperatures is attributed to the synergistic effects of the contraction and expansion configurations of stimuli-responsive polymers, combined with the hybridization-dehybridization event of DNA strands. Importantly, our simulations isolate the conditions of programmable self-assembly of bifunctionalized NPs to realize the multimodal ON-OFF nanoswitches by the changes of temperature and chain rigidity. In addition, it is found that the bifunctionalized NPs in the ON state display anisotropic and patchy features due to an introduction of stimuli-responsive polymers. Our simulation results provide fundamental insights on qualitative predictions of ON/OFF states of DNA-based NPs, which can aid in realizing a set of ON-OFF nanoswitches by the rational design of functionalization molecules.

Marginal Distributions at the Tip of a Grafted Stiff Polymer: Analytical and Monte Carlo Investigations

AbstractThis study investigates the marginal distributions of grafted stiff polymer tips in a 2D embedding space using both analytical methods and Monte Carlo simulations. By mapping active Brownian particle (ABP) trajectories in the short‐time regime, analytical expressions for the elongation of the free end of the polymer under horizontal and vertical forces are derived and these expressions are validated using Monte Carlo simulations. These results indicate that the theoretical predictions match well with the simulation results when the chain length is short or the force is large. However, a slight discrepancy is observed between the theoretical and simulation results when the chain is extremely long, although the qualitative asymptotic results remain valid. Additionally, expressions are provided for the horizontal and vertical force versus displacement for the wormlike chain under the weakly bending approximation. This research provides insights into how the trajectories of an ABP correspond to the equilibrium configuration of a semiflexible polymer. These findings have potential applications in various fields, including biophysics and materials science, where understanding the behavior of grafted polymers is crucial.

Leveraging polymer modeling to reconstruct chromatin connectivity from live images

Chromosomal dynamics plays a central role in a number of critical biological processes, such as transcriptional regulation, genetic recombination, and DNA replication. However, visualization of chromatin is generally limited to live imaging of a few fluorescently labeled chromosomal loci or high-resolution reconstruction of multiple loci from a single time frame. To aid in mapping the underlying chromosomal structure based on parsimonious experimental measurements, we present an exact analytical expression for the evolution of the polymer configuration based on a flexible-polymer model, and we propose an algorithm that tracks the polymer configuration from live images of chromatin marked with several fluorescent marks. Our theory identifies the resolution of microscopy needed to achieve high-accuracy tracking for a given spacing of markers, establishing the statistical confidence in the assignment of genome identity to the visualized marks. We then leverage experimental data of locus-tracking measurements to demonstrate the validity of our modeling approach and to establish a basis for the design of experiments with a desired resolution. Altogether, this work provides a computational approach founded on polymer physics that vastly improves the interpretation of in vivo measurements of biopolymer dynamics.

Bifunctional clay based sorbent for 'Ochratoxin A' removal and wine fining.

The treatment of Ochratoxin A (OTA), present in many agricultural commodities including wine, is unsatisfying even by adsorption to fining agents, such as the commercial clay montmorillonite (MMT), bentonite. We developed, characterized and tested new clay-polymer nanocomposites (CPNs) to optimize OTA treatment, adsorption and OTA-CPN removal by sedimentation, while maintaining product quality. OTA adsorption to the CPNs was optimized, fast and high, by varying polymer chemistry and configuration. OTA adsorption from grape juice was nearly 3 times higher by the CPN than by the MMT despite the larger particle size of the CPN, 125 vs. 3µm, explained by diverse OTA-CPN interactions. The CPN outperformed MMT in terms of sedimentation rate (2-4 orders of magnitude faster), grape juice quality and volume loss (an order of magnitude less), highlighting the potential of applying composites for the removal of target molecules form beverages.

Effect of Structural Changes at Various Length Scales in SiVOC Ceramic Nanocomposites on Electrocatalytic Performance for the Oxygen Reduction Reaction.

Polymer-derived processing of ceramics (PDC) is an efficient technique to prepare porous nanocomposites with precise control over their phase composition and in relation to the Si-based ceramic matrix containing free carbon. The microstructure of these nanocomposites can be fine-tuned at the molecular scale for obtaining necessary properties by tailoring the chemical configuration of the preceramic polymer. In the present work, vanadium-based nanocomposites were synthesized as oxygen reduction reaction (ORR) catalysts with the objective of elucidating the effect of microstructure changes on catalytic efficiency. For this purpose, a single-source precursor (SSP) was synthesized by crosslinking phenyl- and hydrido-substituted polysiloxane and vanadium acetylacetonate followed by pyrolysis at 1100 °C. The resulting solid was composed of sparsely distributed nanodomains of vanadium carbide (VC) crystals precipitated within an amorphous silicon oxycarbide (-Si-O-C-) matrix. High-temperature treatment of the pyrolyzed samples beyond 1300 °C induced the crystallization of β-SiC as well as VC. Furthermore, Raman spectroscopy confirmed the segregation of sp2-hybridized, turbostratic free carbon. The samples exposed to 1300 °C revealed a specific surface area of 239 m2/g. The electrocatalytic activity of the sample heat-treated at 1300 °C showed the best performance with respect to the ORR performance with onset potential (Eo) and half-wave potential (E1/2) values of 0.81 and 0.72 V, respectively. In addition, improved kinetics with a Tafel slope of 57 mV/dec and enhanced current density in the diffusion-controlled region (Id) of 3.7 mA/cm2 were observed for this sample. The increase in Eo was attributed to the optimal interfacial characteristics between the VC and SiOC matrix with better embedment of VC with free carbon through V-C bonds. The higher E1/2 and faster kinetics are because of the higher electronic conductivity caused by the free carbon effectively connecting metallic VC crystallites. Besides, the higher specific surface area of this sample enhanced Id.

Temperature-Responsive Nanoporous Membranes from Self-Assembly of Poly(N-isopropylacrylamide) Hairy Nanoparticles.

Nanoporous membranes play a critical role in numerous separations on laboratory and industrial scales, ranging from water treatment to biotechnology. However, few strategies exist that allow for the preparation of mechanically robust nanoporous membranes whose separation properties can be easily tuned. Here, we introduce a new family of tunable nanoporous membranes based on nanoparticles decorated with temperature-responsive polymer brushes. We prepared mechanically robust membranes from hairy nanoparticles (HNPs) carrying PNIPAM polymer brushes. We assembled the HNPs into thin films through pressure-driven deposition of nanoparticle suspensions and measured the permeability and filtration cutoff of these membranes at different temperatures. The membrane pore diameter at room temperature varied between 10 and 30 nm depending on the polymer length. The water permeability of these membranes could be controlled by temperature, with the effective pore diameter increasing by a factor of 3-6 (up to 100 nm) when the temperature was increased to 60 °C. The size selectivity of these membranes in the filtration of nanoparticles could also be attenuated by temperature. Molecular dynamics computer simulations of a coarse-grained HNP model show that temperature-sensitive pores sizes are consistent with our experimental results and reveal the polymer configurations responsible for the observed filtration membrane permeability. We expect that these membranes will be useful for separations and in the preparation of responsive microfluidic devices.

Translocation of an active polymer into a two dimensional circular nano-container

Translocation dynamics of an active semi-flexible polymer through a nano-pore into a rigid two dimensional circular nano-container has been studied by using Langevin dynamics simulations. The results show that the force exponent β, for regime of small nano-container radius, i.e. , where R g is the gyration radius of the passive semi-flexible polymer in two dimensional free space, is , while for large values of the asymptotic value of the force exponent is . The force exponent is defined by the scaling form of the average translocation time , where F sp is the self-propelling force. Moreover, using the definition of the turning number (number of net turns of the polymer configuration) for the polymer inside the cavity, it has been found that at the end of translocation process for small value of R and in the strong force limit the polymer configuration is more regular than the case in which the value of R is large or the force is weak.