Chain Molecules Research Articles

Compaction and clustering of a heterogeneous polymer by biomolecular crowding.

Inspired by bacterial chromosome organization, we study the compaction and clustering of a heterogeneous ring polymer in a crowded medium using molecular dynamics simulations. The polymer consists of several large monomers interspersed along the backbone and small intervening monomers. In a crowded medium, the entropy of crowding particles or crowders favors the collapse of chain molecules, such as chromosomes. Our study shows that the compaction transition of heterogeneous polymers by crowders is well-correlated with the clustering of large monomers: when the large monomers are sufficiently large, both occur concomitantly in the same narrow (biologically relevant) range of the volume fraction of crowders. It also indicates that cylindrical confinement makes crowding effects more effective. The results presented here suggest that phase separation and clustering are essential features of bacterial chromosome organization.

High‐strength silicone polyurea/DOCIT coating with anti‐biofouling and self‐healing characteristics

AbstractA new organosilicon‐based polyurea/DOCIT composite coating with excellent mechanical, self‐healing characteristics has been successfully prepared in this paper. The optimal ratio of the two isocyanates has been explored to acquire the highest mechanical strength with 8.56 MPa and best tensile properties with 763%. The breaking strength and elongation remain 3.50 MPa and 915% with 1% antimicrobial agent DOCIT. The self‐healing characteristic comes from dense hydrogen and dynamic disulfide bonds between molecule chains. The composite coating exhibited ideal bacterial resistances for 98.02% and 96.75% against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively. The adhesion of chlorella was significantly reduced by approximately 86.48%. This work provides a promising avenue for the development of high‐performance silicone polyurea coatings for marine anti‐biofouling.

First Vesicular Self-Assembly of an Apocarotenoid Bixin in Aqueous Liquids and Its Antibacterial Activity.

Bixin 1 is the major constituent of the reddish carotenoids present in the seed-coat of Bixa orellana. The use of the extract of the seed-coat of Bixa orellana in food, cosmetics and garments is well known. The nano-sized long 24 C chain molecule has nine conjugated double bonds having extended conjugation with the '-COOH' and '-COOMe' groups present at the two ends of the molecule. Herein, we report the first self-assembly of bixin in several aqueous liquids. The molecule undergoes spontaneous self-assembly in several liquids yielding vesicular self-assembly. Characterizations of the self-assemblies of bixin were carried out by various microscopic techniques, X-ray diffraction and FTIR studies. The critical vesicular concentrations (CVCs) of the compound carried out in DMSO-water in three different solvent ratios as 2: 1 (v/v), 1: 1 (v/v) and 1: 4 (v/v) were determined to be 100 μM, 90 μM and 60 μM respectively indicating lower CVC values at higher proportion of water. Utilization of the vesicular self-assemblies of bixin have been demonstrated in the entrapment and release of fluorophores including the anticancer drugs doxorubicin and curcumin. Self-assembled bixin and curcumin loaded self-assembled bixin showed significant antibacterial activity with both Gram positive as well as Gram negative bacteria.

Synthesis, crystal structure and Hirshfeld surface analysis of 2-{4-[(2-chlorophenyl)methyl]-3-methyl-6-oxopyridazin-1-yl}-N-phenylacetamide

In the title molecule, C20H18ClN3O2, the 2-chlorophenyl group is disordered to a small extent [occupancies 0.875 (2)/0.125 (2)]. The phenylacetamide moiety is nearly planar due to a weak, intramolecular C—H...O hydrogen bond. In the crystal, N—H...O hydrogen bonds and π-stacking interactions between pyridazine and phenyl rings form helical chains of molecules in the b-axis direction, which are linked by C—H...O hydrogen bonds and C—H...π(ring) interactions. A Hirshfeld surface analysis was performed, which showed that H...H, C...H/H...C and O...H/H...O interactions to dominate the intermolecular contacts in the crystal.

Regulating V2O5 Layer Spacing by a Polyaniline Molecule Chain to Improve Electrochemical Performance in Salinity Gradient Energy Conversion.

Salinity gradient energy is a chemical potential energy between two solutions with different ionic concentrations, which is also an ocean energy at the junction of rivers and seas. In our original work, the device "activated carbon//(0.083 M Na2SO4, 0.5 M Na2SO4)//vanadium pentoxide" for the conversion of salinity gradient energy was designed, and the conversion value of 6.29 J g-1 was obtained. However, the low specific surface area of the original V2O5 inevitably resulted in limited active sites and slow ionic transport rates, and the inherent lower conductivity and narrower layer spacing of the original V2O5 also resulted in poor electrode kinetic performance and cycle stability, hindering its practical application. To solve the above problems, the present work provides a strategy of using polyaniline (PANI) molecule chain intercalation to regulate the layer spacing of the original V2O5, and through the expansion and traction of the layer spacing, the composite PANI/V2O5 (PVO) with high specific surface area is prepared and used as an anode material for electrochemical conversion of salinity gradient energy application. The significantly increased layer spacing of the crystal plane (001) corresponding to the original V2O5 was confirmed with the PANI by the hydrogen bonding and the van der Waals force. The high specific surface area of the composite provides more electrochemical active sites to realize a fast Na+ migration rate and high specific capacitance. Meanwhile, the inserted PANI molecule chain, which acts not only as a pillar enlarging the Na+ diffusion channel but also as an anchor locking the gap between V2O5 bilayers, improves the structural stability of the V2O5 electrode during the electrochemical conversion process. The proposed insertion strategy for the conductive polymer PANI has created a new way to improve the cycle stability performance of the salinity gradient energy conversion device.

Crystal structure and Hirshfeld surface analyses, crystal voids, intermolecular interaction energies and energy frameworks of 3-benzyl-1-(3-bromopropyl)-5,5-diphenylimidazolidine-2,4-dione

The title molecule, C25H23BrN2O2, adopts a cup shaped conformation with the distinctly ruffled imidazolidine ring as the base. In the crystal, weak C—H...O hydrogen bonds and C—H...π(ring) interactions form helical chains of molecules extending along the b-axis direction that are linked by additional weak C—H...π(ring) interactions across inversion centres. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H...H (51.0%), C...H/H...C (21.3%), Br...H/H...Br (12.8%) and O...H/H...O (12.4%) interactions. The volume of the crystal voids and the percentage of free space were calculated to be 251.24 Å3 and 11.71%, respectively, showing that there is no large cavity in the crystal packing. Evaluation of the electrostatic, dispersion and total energy frameworks indicate that the stabilization is dominated by the dispersion energy.

Lightweight and highly heat-resistant copolymerized polyimide foams for superior thermal insulation and acoustic absorption

The development of lightweight and highly heat-resistant polyimide foams (PIFs) remains a great challenge in areas of aerospace, military ships, transportation, and industries. Herein, a series of lightweight and highly thermal-resistant copolymerized PIFs are successfully fabricated by the “stepwise heating-holding” thermal foaming of the copolymerized polyester ammonium salts (C-PEAS), using 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA) and 2,3,3′,4′-biphenyl tetracarboxylic acid dianhydride (α-BPDA) as codianhydride, and p-phenylenediamine (PDA) as diamine. The introduction of α-BPDA increases the rigidity of PI molecule chains and foamability of C-PEAS, and significantly improves the heat resistance of PIFs. The resultant copolymerized PIFs exhibit ultra-low densities (<10 kg·m-3), excellent heat resistance (Tg ranging from 351.2°C to 405.6°C), and high thermal stability. Moreover, they possess high flame retardancies (LOI>44%) and low thermal conductivities (as low as 0.0463 W·m-1∙K-1 at 20°C and no more than 0.0825 W·m-1∙K-1 at 200°C), demonstrating their excellent thermal insulation properties in a wide temperature range. After the continuous heating at 200°C for 40 min, the upper surface of PIFs present low average temperatures less than 60°C. Additionally, the copolymerized PIFs exhibit remarkable acoustic properties with average acoustic absorption coefficients above 0.6 and noise reduction coefficients (NRC) above 0.3. Therefore, the lightweight and highly heat-resistant copolymerized PIFs show great application potentials in the extreme environments of aerospace, military ships, transportation, and industries.

Suitability of early indica rice for the preparation of rice noodles by its starch properties analysis

The research was conducted to explore the affiliation between the physicochemical properties of rice noodles and rice starch of early indica rice samples of varying amylose content. 3 various types of rice samples were analyzed to uncover how amylose content influences rice noodles' quality. Findings revealed that primarily sensory scores differ in palatability, while textural disparity lies in hardness and chewiness. The higher hardness and chewiness values were correlated with higher sensory scores. Rice with lower amylose content demonstrates elevated solubility, swelling power, and crystallinity along with poor retrogradation resulting in inferior-quality noodles. Sensory scores and textural properties were proved to be associated with the distribution of branched starch molecule chain lengths. Noodles of higher sensory scores had more stable gel structure and improved elasticity. These findings underscore the critical role of amylose content and starch molecular structure in determining the suitability of early indica rice for noodle preparation.

Enhancing emulsion stability and adsorption of Pickering emulsions using alkylated cellulose nanofibers

Cellulose nanofibers (CNFs) extracted from plant cell walls form a three-dimensional network in water and stabilize the dispersion of droplets, which are used as emulsion stabilizers. In this study, four types of alkyl-grafted CNFs (ACNFs) with different lengths of dialkyl chains (diC4, diC6, diC8, and diC10) were synthesized by the surface modification of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized CNF (TOCNF) to improve the stability of oil-in-water Pickering emulsions (PEs). The ACNF-stabilized emulsions with a 20/80 ratio of oil/water were prepared using two different oils (olive oil and eucalyptus oil) and the ACNF 1.0 % dispersion, and the changes over time were investigated at approximately 25 °C. Compared to TOCNF, the ACNFs provided more stable olive oil-PE (o-PE) and eucalyptus oil-PE (e-PE) although the stabilization behaviors of o-PE and e-PE differed. Olive oil, which contained rich long-chain fatty acids, was more likely to interact with the ACNFs, thereby promoting the interfacial adsorption of oil droplets. On the other hand, eucalyptus oil is mainly composed of 1,8-cineole and does not have alkyl chains, so the interaction with the ACNFs was weak and therefore, sufficient interfacial adsorption could not be obtained. The results of the particle size distribution and viscosity measurements also showed that the ACNFs contributed significantly to the stabilization of o-PE. Based on the overall experimental results, it was determined that the diC6-ACNF gave the most significant stability improvement. Therefore, we designed an alkylated CNF that mimics diC6-ACNF for MD simulations. MD simulations showed that hydrophobic modification created a hydrophobic interaction between the alkyl chain and dodecane molecules as the oil, leading to the enhancing adsorption of ACNF at the oil droplet interfaces.

Tailoring closed pore structure in phenolic resin derived hard carbon enables excellent sodium ion storage

The existed plenty of oxygen-containing species in phenolic resin easily inhibit the migration and rearrangement of carbon atoms during pyrolysis, which disfavors the formation of pseudo-graphite structure with larger lateral length (La) and hence leads to poor closed pores, accounting for a low capacity and initial Coulombic efficiency (ICE). Herein, hard carbon with rich closed pores and the most suitable pore size and volume is constructed via a two-step carbonization strategy. It is found that the pre-annealing step can effectively decrease oxygen content by changing the interconnection form of molecule chains, which promotes the growth of La during post-carbonization process, accelerating the formation of closed pores. Besides, with decreasing oxygen content, closed pore size gradually increases, while closed pore number and volume both first increase and then decrease, unveiling that an excessive high and too low oxygen content are unfavorable for the formation of ideal closed pores, resulting from an unsuitable La size. Therefore, the resulting sample, featured by the optimal balance between closed pore number, size (2.52 nm), and volume (0.215 cm3 g−1), delivers a high capacity of 351 mAh g−1 along with an excellent ICE of 83 %.

Unveiling the reaction mechanism of arginine decarboxylase in Aspergillus oryzae: Insights from crystal structure analysis

Agmatine, a natural polyamine also known as 4-aminobutyl-guanidine, is biosynthesized from arginine by decarboxylation. Aspergillus oryzae contains high amounts of agmatine, suggesting highly active arginine decarboxylase (ADC) in this organism. However, genome analysis revealed no ADC homolog in A. oryzae. A. oryzae strain RIB40 has six homologs of phosphatidylserine decarboxylase (PSD), an enzyme that synthesizes phosphatidyl ethanolamine from phosphatidylserine. We previously discovered that one of these homologs, AO090102000327, encodes arginine decarboxylase, which we named ADC1. In the present study, we determined the crystal structures of ligand-free, arginine-treated, and agmatine-treated ADC1 each at 1.9–2.15 Å resolution. Each structure contained four ADC1 molecules (chains A–D) in the asymmetric unit of the cell. Each ADC1 molecule is a heterodimer consisting of the N-terminal region (Asn60–Gly441) and C-terminal region (Ser442–Thr482). In the ligand-free ADC1, the N-terminus of Ser442 was modified to form a pyruvoyl group. In the arginine-treated ADC1, arginine was converted to agmatine, with the pyruvoyl group covalently bound to agmatine by forming a Schiff base. The same structure was observed in agmatine-treated ADC1. These results indicate that ADC1 is a pyruvoyl-dependent decarboxylase and unveils the reaction mechanism of ADC from A. oryzae.

Theoretical Insight into Fluorination on Low‐Cost A‐π‐D‐π‐A Type Donor Materials for All‐Small‐Molecule Organic Photovoltaic Cells

Low‐cost organic photovoltaic (OPV) devices have shown enormous potential in large‐scale industrial applications. And it has attracted widespread attention in the past few decades. However, the photophysical characteristics of these budget‐friendly materials haven't been explored much. Here, low‐cost small materials, including small molecule 1 (asm1) with ortho‐fluorinated side chain and small molecule 2 (asm2) with meta‐fluorinated side chain were selected to probe the fluorination effect on the absorption spectra, electrochemical energy levels, electrostatic potential (ESP), etc. The results show that the molecules asm1 and asm2 have good planarity of the backbone. And the meta‐fluorinated side chain of asm2 contributes more to the highest occupied molecular orbital and less to the lowest unoccupied molecular orbital than asm1. Moreover, differences in ESP are found between donor and acceptor materials. Furthermore, strong and broad light absorption in the visible region of these low‐cost molecules is observed, resulting in a better short‐circuit current density for the devices constructed by the donors asm1, asm2, and acceptor Y6. In addition, more charge transfer mechanisms are characterized for the asm1/Y6 system. The introduction of ortho‐fluorination in the conjugated side chain of the molecule is a favorable approach, which will provide theoretical guidance for further molecular design experiments.

Advanced Crosslinked Solid Polymer Electrolytes: Molecular Architecture, Strategies, and Future Perspectives

AbstractSolid‐state batteries (SSBs) have attracted much attention for high‐energy‐density and high‐safety energy storage devices. Solid polymer electrolytes (SPEs) have emerged as a critical component in the advancement of SSBs, owing to the compelling advantages of strong molecular structure‐designability, low cost, easy manufacturing, and no liquid leakage. However, linear SPEs usually have low room‐temperature ionic conductivity due to crystallization, and melting at high temperature. Thus, crosslinked SPEs have been proposed in that the chemical bonding between internal molecule chains can maintain solid state to expand operational temperature, disrupt regularity of segment, and diminish crystalline degree, leading to an enhancement of room‐temperature ionic conductivity. Furthermore, the integration of functional groups within crosslinked SPE network can significantly augment the electrochemical performance of SPEs. Herein, according to the network structure, crosslinked SPEs are categorized into four types: simple network, AB crosslinked polymers (ABCP), semi‐interpenetrating network (semi‐IPN), and interpenetrating network (IPN), then the structure features and advantages and disadvantages of commonly used polymers for these types of crosslinked SPEs are reviewed. In addition, crosslinked SPEs with self‐healing, flame‐retardant, degradable, and recyclability are introduced. Finally, challenges and prospects of crosslinked SPEs are summarized, hoping to provide guidance for the molecular design of SPEs in the future.

Heat-Excitation-Based Triboelectric Charge Promotion Strategy.

The surface charge decay is observed at high temperatures due to thermionic emission, which, however, may not be the only mechanism contributing to the surface charge variation. Here, a triboelectric charge promotion strategy due to the heat-excitation effect of hot electrons near the fermi level is demonstrated, while the final charge is determined by the balance between thermionic emission and the heat-excitation effect. It is demonstrated that metals with lower work function exhibit a better heat excitation capability, and polymers with lower fluorine content in molecule chains further boost the charge output, where metal/Kapton pairs demonstrated a charge promotion of over 2 times at the temperature of 383K with good durability during 90min measurement. The heat-excitation effect and charge durability in sliding freestanding-triboelectric-layer (SFT) mode triboelectric nanogenerator (TENG) is demonstrated as well, where the energy is promoted by over 3 times and the capacitor charging speed is doubled as well, with an energy promotion from 109.34 to 373µJ per cycle to successfully trigger a discharger. This work suggests a promising future of the heat-excitation effect as a new charge promotion strategy for TENG toward different applications in high-temperature environments.

Molecular Simulation Analysis of Polyurethane Molecular Structure under External Electric Field.

Polyurethane (PU) materials are extensively utilized in power equipment. This paper introduces a comprehensive evaluation method that combines electromagnetics and computational chemistry based on the Density Functional Theory (DFT) to elucidate the impact of external electric fields on the molecular structure of PU during electrical contact. The study focuses on the microstructural and molecular energy changes in the hard (HS) and soft (SS) segments of PU under the influence of an electric field of uniform intensity. Findings indicate that the total energy of HS molecules decreases markedly as the electric field intensity increases, accompanied by a significant rise in both the dipole moment and polarizability. Conversely, the total energy and polarizability of the SS molecules decrease, while the dipole moment experiences a slight increase. Under the influence of a strong electric field, HS molecules tend to stretch towards the extremities of the main chain, leading to structural instability and the cleavage of hydroxyl O-H bonds. Meanwhile, the carbon chain of the SS molecules twists towards the center under the electric field, with no chemical bond rupture observed. At an electric field intensity of 8.227 V/nm, the HOMO-LUMO gap of the HS molecule narrows sharply, signifying a rapid decline in the molecular structure stability, corroborated by infrared spectroscopy analysis. These findings offer theoretical insights and guidance for the modification of PU materials in power equipment applications.

Preparation and characterization of cardanol based vinyl ester resins as cross‐linker units

AbstractIn this study, two cardanol based epoxidized resins, NC514 with less than two epoxies per molecule and side chain epoxidized cardanol glycidyl ether (SCECGE) with approximately 2.45 epoxies (1.0 phenolic+1.45 aliphatic epoxies) per molecule were methacrylated. The methacrylated versions of cardanol based NC514 (NC514VE) and SCECGE (SCECGEVE) epoxy resins were used as cross‐linker units in vinyl ester formulations with methacrylated lauric acid (MFA) and styrene (ST) as bio‐based and synthetic based reactive diluents respectively, at various concentrations (10–40 wt%). The curing reactions of the resins were studied via FTIR and the extent of polymerization was determined for different cross‐linker units in the presence of ST and MFA. Our mechanical and thermomechanical characterizations showed that VER formulations prepared with cardanol based SCECGEVE cross‐linker unit have significantly improved properties than the samples prepared with commercially available counterpart NC514VE using either reactive diluent. These properties of SCECGEVE were also comparable with to that of methacrylated petroleum‐based diglycidyl ether of bisphenol A vinyl ester (DGEBAVE) formulations unlike NC514VE formulations due to more effective side chain functionalization and cross‐linking.

Electric field modulated configuration and orientation of aqueous molecule chains.

Understanding how external electric fields (EFs) impact the properties of aqueous molecules is crucial for various applications in chemistry, biology, and engineering. In this paper, we present a study utilizing molecular dynamics simulation to explore how direct-current (DC) and alternative-current (AC) EFs affect hydrophobic (n-triacontane) and hydrophilic (PEG-10) oligomer chains. Through a machine learning approach, we extract a 2-dimensional free energy (FE) landscape of these molecules, revealing that electric fields modulate the FE landscape to favor stretched configurations and enhance the alignment of the chain with the electric field. Our observations indicate that DC EFs have a more prominent impact on modulation compared to AC EFs and that EFs have a stronger effect on hydrophobic chains than on hydrophilic oligomers. We analyze the orientation of water dipole moments and hydrogen bonds, finding that EFs align water molecules and induce more directional hydrogen bond networks, forming 1D water structures. This favors the stretched configuration and alignment of the studied oligomers simultaneously, as it minimizes the disruption of 1D structures. This research deepens our understanding of the mechanisms by which electric fields modulate molecular properties and could guide the broader application of EFs to control other aqueous molecules, such as proteins or biomolecules.

Research Progress in Starch-based Dye Adsorbents

Abstract: Starch is a typical environment-friendly biomass material and there are considerable quantities of reactive hydroxyl groups in the starch molecule chain. Modifications could introduce a large number of functional groups, which can bind some dyeing contaminants, thereby removing the dyes. According to the different modification methods, starch-based adsorbents can be divided into three categories that are aminated-modified starch, ionic-modified starch, and composite-modified starch. The preparation method, structure properties, and adsorption capacity of modified starch dye adsorbents have been reviewed in this article. It can be concluded that the adsorption property of adsorbents depends on different adsorption conditions and modification methods. The adsorption properties of the adsorbents have been found to be influenced by temperature, initial concentration of dyes, and pH value of solution. Amination modification can introduce amino or amine groups into the starch skeleton to enhance the chelation or electrostatic effect of the adsorbents on dyes. Ion modification can improve the ion exchange and electrostatic interaction between the adsorbents and the dye. Composite modification can improve specific surface area, pore size, adsorption site, and structural stability of the adsorbents. Future studies are required to focus on producing dye adsorbents with high adsorption performance, stable structure, recyclability, and degradability.

Adsorption of Prochiral Solvent Molecules by Surface-Confined Chiral Supramolecular Assemblies: How Solvent Impacts on-Surface Chirality.

The understanding of supramolecular chirality in self-assembled molecular networks (SAMNs) on surfaces generates a lot of interest because of its relation to the production of chiral sensors, reactors, and catalysts. We herein report the adsorption of a prochiral solvent molecule in porous SAMNs formed by a chiral dehydrobenzo[12]annulene (cDBA) derivative. Through the prochirality recognition of a solvent molecule, the supramolecular chirality of the SAMN is switched: the cDBA exclusively forms a counter-clockwise pore through co-adsorption of the solvent molecule in prochiral 1,2,4-trichlorobenzene, while in 1-phenyloctane it produces the opposite chiral, clockwise pore. The prochirality recognition of the solvent molecule in the chiral SAMN pores is attributed to the adaptable conformational changes of the chiral chains of the cDBA molecule.

Quasi-one-dimensional hydrogen bonding in nanoconfined ice

The Bernal-Fowler ice rules stipulate that each water molecule in an ice crystal should form four hydrogen bonds. However, in extreme or constrained conditions, the arrangement of water molecules deviates from conventional ice rules, resulting in properties significantly different from bulk water. In this study, we employ machine learning-driven first-principles simulations to identify a new stabilization mechanism in nanoconfined ice phases. Instead of forming four hydrogen bonds, nanoconfined crystalline ice can form a quasi-one-dimensional hydrogen-bonded structure that exhibits only two hydrogen bonds per water molecule. These structures consist of strongly hydrogen-bonded linear chains of water molecules that zig-zag along one dimension, stabilized by van der Waals interactions that stack these chains along the other dimension. The unusual interplay of hydrogen bonding and van der Waals interactions in nanoconfined ice results in atypical proton behavior such as potential ferroelectric behavior, low dielectric response, and long-range proton dynamics.