Condensed State Structure Research Articles

Co/C Nanocomposites with Tunable Condensed States Induced by Conformation-Mediated Strategy for Electromagnetic Wave Absorption.

The strategic regulation of condensed state structures in multicomponent nanomaterials has emerged as an effective approach for achieving controllable electromagnetic (EM) properties. Herein, a novel conformation-mediated strategy is proposed to manipulate the condensed states of Co and C, as well as their interaction. The conformation of polyvinylpyrrolidone molecules is adjusted using a gradient methanol/water ratio, whereby the coordination dynamic equilibrium effectively governs the deposition of metal-organic framework precursors. This process ultimately influences the combined impact of derived Co and C in the resulting Co/C nanocomposites post-pyrolysis. The experimental results show that the condensed state structure of Co/C nanocomposites transitions from agglomerate state → to biphasic compact state → to loose packing state. Benefiting from the tunable collaboration between interfacial polarization and defects polarization, and the appropriate electrical conductivity, the diphasic compact state of Co/C nanocomposites achieves an effective absorbing bandwidth of 7.12GHz (2.1mm) and minimum reflection loss of -32.8dB. This study highlights the significance of condensed state manipulation in comprehensively regulating the EM wave absorption characteristics of carbon-based magnetic metal nanocomposites, encompassing factors such as conductivity loss, magnetic loss, defect polarization, and interface polarization.

Liquefied Polysaccharides-Based Polymer with Tunable Condensed State Structure for Antimicrobial Shield by Multiple Processing Methods.

The phase behavior of biomolecules containing persistent molecular entities is generally limited due to their characteristic size that exceeds the intermolecular force field. Consequently, favorable properties normally associated with the liquid phase of a substance, such as fluidity or processability, are not relevant for the processing of biomolecules, thus hindering the optimal processing of biomolecules. The implied problem that arises is how to convert folded biomolecules to display a richer phase behavior. To alleviate this dilemma, a generic approach to liquefied polysaccharides-based polymers is proposed, resulting in a polysaccharide fluid with a tunable condensed state structure (solid-gel-liquid). Polysaccharide biobased fluids materials transcend the limits of the physical state of the biobased material itself and can even create completely new properties (different processing methods as well as functions) in a variety of polymeric structures. Considering the solvent incompatible high and low-temperature applications, this method will have a great influence on the design of nanostructures of biomolecular derivatives and is expected to transform biomass materials such as polysaccharide biopolymers from traditional use to resource use, ultimately leading to the efficient use of biomass materials and their sustainability.

Based on the Second Virial Coefficient (A2) to Study Effect of the Synergistic Action of Solvent and External Electric Field on the Solution Behavior and Film’s Condensed State Structure

Based on the Second Virial Coefficient (A2) to Study Effect of the Synergistic Action of Solvent and External Electric Field on the Solution Behavior and Film’s Condensed State Structure

Study of the Chain Condensation Process from a Dilute to a Concentrated Solution and the Transformation of the Chain Conformation from a Solution to a Film for the Conjugated Polymer PFO.

The chain behavior in a precursor solution and its condensation process are still key issues that have been paid close attention to but have not been solved yet for semirigid conjugated polymers. In this research, the chain condensation process from a dilute to a concentrated solution and the transformation of the chain conformation from a solution to a film for the conjugated polymer poly(9,9′-dioctylfluorene) (PFO) were investigated by a scaling law method obtained from rheological measurements. By establishing a scaling relationship between specific viscosity and concentration, it was found that the motion of molecular chains conformed to the Zimm model in dilute solution, and the motion of molecular chains conformed to the Rouse model in semidilute unentangled solution as well as conformed to the Edwards tube model in semidilute entangled solution. Furthermore, it was also found that toluene is a θ solvent for PFO at 25 °C. Some important physical parameters in connection with PFO intrinsic properties were also obtained here, such as intrinsic viscosity [η] = 136.84 mL g–1, root-mean-square end-to-end distance R = 41.4 nm, and Kuhn segment length b = 6.28 nm. In particular, this was the first time that the effect of the film-forming process of spin coating on the transformation proces of the PFO chain conformation from the precursor solution to a film was studied, and the spin-coating time (t) was found to be several orders of magnitude longer than the PFO chain relaxation time (τZ(τR)). This research enriches knowledge and understanding of the chain behavior in the precursor solution for semirigid conjugated polymers and reveals the correlation of chain behaviors in solution with the film’s condensed state structure in the process of chain dynamic evolution from a solution to a film.

Influence of molecular weight and the change of solvent solubility on β conformation and chains condensed state structure for poly (9,9-dioctylfluorene) (PFO) in solution

Molecular weight has a significant influence on the performance of conjugated polymer photoelectronic devices. However, so far, few detailed researches have focused on solution-related properties such as chain conformation and condensed state structure. In this work, the influence of molecular weight and the change of solvent solubility on the single-chain conformation, aggregation state structure and ordered β conformation of Poly (9,9-dioctylfluorene) (PFO) was investigated. We found that the formation of PFO β conformation had a direct relationship with chain length. Among the six samples with different molecular weights, the size of aggregations and the content of β conformation increased with the increase of molecular weight after adding the poor solvent acetone into toluene solution directly. There was almost no β conformation in aggregation or precipitation of the lowest molecular weight. We speculated that the β conformation was mainly formed by the folding of single-chain, because polymer chain of higher molecular weight was longer and more flexible for conformational and orientational transformation. Meanwhile, we found an interesting phenomenon that the β conformation formation was strongly affected by the changing rate of solvent solubility. The possible mechanism of the related phenomenon was revealed. This research provides not only a profound understanding of the formation process and mechanism of the ordered structures of semi-rigid conjugated polymer in solution, but also a theoretical basis for manipulating the condensed state structure of films in the application of photoelectronic devices from the perspective of conjugated polymer physics.

Effect and Mechanism of Solvent Properties on Solution Behavior and Films Condensed State Structure for the Semi-rigid Conjugated Polymers

Solvents have an essential association with polymer solution behavior. However, few researches have been deeply done on this respect. In recent years, our research group focus on the study on effect of solvent properties on solution behavior and film condensed state structure for semi-rigid conjugated polymer up till to apply for optoelectronic device. Herein, influence of solvent properties including solubility of solvent, aromaticity, polarity and hydrogen bonds on semi-rigid polymer chain solution behavior, i.e., single chain conformation, chain shape, size and chains aggregated density were studied by means of static/dynamic laser light scattering (DLS/SLS) and exponential law etc. Effect of solvent properties on condensed state structure of the semi-rigid conjugated polymer film was studied by UV absorption spectroscopy, PL spectroscopy and electron microscopy etc. The essential reasons for the influence were discovered and the mechanism was revealed. It was found that solution behavior with different solvent properties had an essential physical relationship with chains condensed state structure of the semi-rigid conjugated polymers. More importantly, there was a quantitative structure-activity relationship between solution and film. The key to this relationship depended on the interaction between solvent molecules and the semi-rigid conjugated polymer chains. This interaction could also affect optoelectronic devices performance. This study is of great significance to effectively control the condensed state structure of the semirigid conjugated polymers in the process of dynamic evolution from solutions to films. It not only enriches the knowledge and understanding of both semi-rigid conjugated polymer solution behaviors and film condensed state physics based on polymer physics, but also is meaningful to practical application for conjugated polymer and other traditional polymer systems.

Probing into the microstructural evolution of isotactic polypropylene during photo-oxidation degradation

Photo-oxidation degradation behavior of isotactic polypropylene (iPP) has been extensively investigated, however, there are still some ambiguous points, e.g., the origin of improved crystallinity at the early stage of photo-oxidation, the evolution of condensed state structure during the process of UV light irradiation, etc. In the present work, iPP film samples, unstabilized and stabilized with a specific reactive hindered amine light stabilizer (RHALS), were exposed to UV irradiation for accelerated aging tests. The microstructural evolution of the samples was systematically investigated by combination of Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). The results show that chemi-crystallization exists both in unstabilized and stabilized iPP, but the chemi-crystallization extent is much lower in the stabilized iPP. In addition to chemi-crystallization, the loss of amorphous region induced by “UV light etching” is another probable factor contributing to the increase of crystallinity at the early stage of photo-oxidation. AFM results provide direct evidence that with the progress of photo-oxidation, the degradation gradually propagates from amorphous region to crystalline region, thus inducing the destruction of lamellar structure. On the basis of above results, a comprehensive model is summarized for the structure evolution of iPP film during photo-oxidation and will be of meaningful reference to the degradation investigation of other semi-crystalline polymeric materials.

WITHDRAWN: Green Fabrication Method of Layered and Open-Cell Polylactide Foams for Oil-Sorption via Pre-Crystallization and Supercritical CO2-Induced Melting

Abstract This paper investigated the condensed state structure evolution of pre-crystallized polylactide (PLA) under supercritical CO2 (scCO2) and its influence on the foaming behavior of PLA. An interesting phenomenon was found, in which the pre-crystallized PLA can form a layered condensed state structure with a molten skin layer and a crystalline core at low temperatures under scCO2, and as the temperature increases, the width of the molten skin layer and the melting degree of the core gradually increases until a uniform non-layered molten state structure is formed. On this basis, layered and non-layered PLA foams were prepared at low and high temperatures, respectively. For the non-layered PLA foam, the skin layer and the core show similar closed or opened cell structure, where the open-cell PLA foams exhibit excellent oil-sorption properties. This paper provides a solvent-free idea for the green fabrication of bio-based and biodegradable oil-sorption foam.

Green fabrication method of layered and open-cell polylactide foams for oil-sorption via pre-crystallization and supercritical CO2-induced melting

This paper investigated the condensed state structure evolution of pre-crystallized polylactide (PLA) under supercritical CO2 (scCO2) and its influence on the foaming behavior of PLA. An interesting phenomenon was found, in which the pre-crystallized PLA can form a layered condensed state structure with a molten skin layer and a crystalline core at low temperatures under scCO2, and as the temperature increases, the width of the molten skin layer and the melting degree of the core gradually increases until a uniform non-layered molten state structure is formed. On this basis, layered and non-layered PLA foams were prepared at low and high temperatures, respectively. For the non-layered PLA foam, the skin layer and the core show similar closed or opened cell structure, where the open-cell PLA foams exhibit excellent oil-sorption properties. This paper provides a solvent-free idea for the green fabrication of bio-based and biodegradable oil-sorption foam.

Controlling condensed state structures of different polar conjugated polymer polyfluorenes (PFs) by applying an external electric field across a solution with polar solvent THF

In this work, controlling condensed state structures of different polar conjugated polymer polyfluorenes (PFs) by applying an external electric field across a solution with polar solvent THF, was investigated.

Effect of solvent aromaticity on poly(9,9-dioctylfluorene) (PFO) chain solution behavior and film condensed state structure

Solvent media is crucial to the dynamic evolution process of conjugated polymer condensed state structures from solution state to film. Especially, aromatic solvent can arouse strong π-π interaction with conjugated polymer backbone. Poly(9,9-dioctylfluorene) (PFO) is a classic hairy-rod conjugated polymer. Chlorobenzene (CB) and toluene (Tol) were used as aromatic solvents, while tetrahydrofuran (THF) and chloroform (CF) were used as non-aromatic solvents. It was firstly found that PFO chain solution behaviors were closely connected to solvent aromaticity with broad concentration range from 0.005 mg/mL to 5 mg/mL. Owing to the bigger chain exclude volume in CB and Tol solvents, in dilute solution with PFO concentration ≤ 0.7 mg/mL, PFO single chains adopted more extended and rigid chain conformation than those in THF and CF solvents, thus, needed conjugated length of β conformation could be easily achieved, and β conformation could be firstly formed; PFO solution concentration increased to ≥ 1 mg/mL, chain aggregation began formation, but aggregation sizes were larger meanwhile chain packing density decreased according to the fractal dimension parameter df; Until PFO solution concentration increased to ≥ 3 mg/mL, only β conformation characteristic peaks began appearance in the all PL spectra. The different solution state behaviors directly affect film condensed structures. A fiber and ordered structure formed in films from CB and Tol solvents, meanwhile circular sheet and short rod-like morphology formed in films from THF and CF solvents, respectively. Solvent effect is significant not only to deeply understand the physical essence both condensed state structure formation and photoelectric performance enhancement but also to well control conjugated polymer condensed state structure to achieve photoelectric devices with high efficiency and stability.

Effect of Solvents on the Solution State and Film Condensed State Structures of a Polyfluorene Conjugated Polymer in the Dynamic Evolution Process from Solution to Film

Although much progress has been made in basic research on conjugated polymers and their practical applications in optoelectronic devices, so far research on the solution state, especially on the effect of solvent on conjugated polymers solution state and films condensed state structure in the dynamic evolution process from solution to film, is scarce. In this research, we focused on a special polyfluorene conjugated polymer, poly(9-(4-(octyloxy)phenyl)-2,7-fluoren-9-ol) (PPFOH), hydrogen bonding with supramolecular conjugated polymers in which intermolecular hydrogen bonds could be formed with different solvents, to explore the effect of solvents on PPFOH’s solution state and the film’s condensed state structure in the dynamic evolution process from solution to film. Dynamic/static light scattering, giving shape parameters and fractal dimension, UV–vis absorption spectra, photoluminescence spectra, fluorescence lifetime measurements, and transmission electron microscopy were used for this research. It was...

Dynamic Evolution from Chain Disorder to Order of PTB7 Condensed State Structures under External Fields.

In this research, the effect of external fields (solvent, temperature, solution concentration, and external force) on dynamic evolution from chain disorder to order of poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2- b:4,5- b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4- b]thiophenediyl]] (PTB7) condensed state structures was explored by UV-vis absorption spectra, atomic force microscope, and transmission electron microscopy (TEM). It was found that PTB7 main chains presented amorphous conformations induced by the poor solvent 1,2-dichloroethane. However, the local ordered aggregation appeared in amorphous conformations when the solubility of the poor solvent was again lowered by reducing temperature. It is worth noting that the size of ordered aggregation was further increased with the decrease of solution concentration or increase of external force. It was found that there were two main PTB7 absorption peaks in the UV-vis absorption spectra; we denoted A0-0 for the intensity of the lower energy absorption peak and A0-1 for the intensity of the higher energy absorption peak. The ratio R = A0-0/ A0-1 was used to characterize the dynamic evolution from disorder to order of the PTB7 condensed state structures in absorption spectra. It increased from 0.94 for PTB7 amorphous state to 1.25 for PTB7 large-size ordered aggregation. The dynamic evolution from chain disorder to order could also be distinctly observed by TEM. It was inferred that PTB7 condensed state structures (amorphous state, local ordered aggregation, and large-scale ordered aggregation) might exist simultaneously because of the complexity of copolymer conformations. This research is meaningful to establish physical basis for the molecule design and the synthesis of materials to enhance photoelectronic device efficiency based on condensed matter physics of conjugated polymer.

Photophysical properties of poly(phenylene-co-fluorene) synthesized via solid-state oxidative coupling polymerization

A series of benzene-co-fluorene copolymers were synthesized via solid-state oxidative coupling polymerization using FeCl3 as the oxidation catalyst. The structural characterization results confirm that the products are random copolymers composed of 1,4-linked phenylene units and 2,7-linked fluorene units. All the copolymers exhibited good thermal stability. The DSC and XRD results showed that the crystallization of copolymers increased with the increasing fluorene units in the backbones. The relationships among molecular structure, condensed-state structure, and photophysical properties of these polymers were investigated by UV–vis absorption spectroscopy and photoluminescence spectroscopy. The optical properties could be adjusted by using different ratios of fluorene and dibutoxybenzene. Moreover, the polymer concentrations and states affected the emission properties of copolymers. This can be attributed to the change in the effective conjugation length of single polymer and the formation of polymer aggregates and excimers. These unique properties endow the benzene-co-fluorene copolymers with potential applications in optoelectronics.

Fluxible poly(p-phenyleneterephthalamide)-based polymer with tunable condensed state structure and controllable rheology behaviors

The non-flow property for rigid-rod polymers remains a serious problem that limits their application on a massive scale. Based on a water-in-oil microemulsion method and one pot in situ “grafting to” strategy, a series of novel poly(p-phenylene terephthalamide)-based materials containing controllable graft density of long-chain tertiary amine are prepared. Consequently, the materials’ rheology behaviors are controllable at the level of an order of magnitude and are well-matched with the tunable condensed state structures. Several significant micro-structures of such liquid-like poly(p-phenylene terephthalamide)-based materials are obtained. Additionally, the excellent solubility conforms to the liquid crystal states, solving the key problem of only dissolving concentrated sulfur acid. Additionally, we further investigated the liquid crystal states in different solvents, mass ratios and temperature. This state-of-the-art material with its established property-structure relationship, especially regarding how the structure determines the rheology behavior and solubility, can be treated as a prototype for guiding future research on ionic liquids and in the field related to functional polymer science and technology. Furthermore, the dielectric properties of f-PPTA/PVDF composite membranes have been investigated and show great potential for use in capacitor applications.

Study on the forming condition and mechanism of the β conformation in poly (9,9-dioctylfluorene) solution

In this work, the forming condition and mechanism of the β conformation in poly (9,9-dioctylfluorene) (PFO) solution are studied. We find the forming condition of β conformation is strongly associated with the proportion of the poor solvent (ethanol) in mixed solution (toluene/ethanol). When the proportion of poor solvent is less than 40% (volume ratio), there is no β conformation in solution; but if the proportion of poor solvent increases to 40%, the β conformation starts to appear. Static and Dynamic Light Scattering research reveal that the molecular chains become collapsed; meanwhile the degree of aggregation is also enhanced when the ethanol proportion increases and proved by TEM. By changing the PFO concentration, we find the concentrations have great influence on the chains aggregation but little influence on the content of β conformation. So we infer the β conformation was formed not in solution but in aggregation, the forming reason was proved to be both intrachain interaction in single chain itself as well as interchain intraction with neighbors in aggregation, which were all enhanced by adding ethanol proportion. The study has a potential meaning to make optoelectronic films whose the condensed state structure was mostly decided by the precursor solution with high charge carrier mobility and devices efficiency by controlling the content of β conformation in PFO precursor solution.

Effects of chain entanglement on liquid-liquid phase separation behavior of LCST-type polymer blends: Cloud point and decomposition rate

By preparing homogenous blend samples with different degrees of chain entanglement, we report an anomalous contribution of chain entanglement to phase separation temperature and rate of poly(methyl methacrylate)/poly(styrene-co-maleic anhydride) (PMMA/SMA) blends presenting a typical lower critical solution temperature (LCST) behavior. The meltmixed PMMA/SMA blends with a higher chain entanglement density present a lower cloud point (Tc) and shorter delay time, but lower phase separation rate at the given temperature than solution-cast ones, suggesting that for the polymer blends with different condensed state structure, thermodynamically more facilitation to phase separation (lower Tc) is not necessarily equivalent to faster kinetics (decomposition rate). The experimental results indicate that the lower Tc of melt-mixed sample is ascribed to smaller concentration fluctuation wavelength (Λm) induced by higher entanglement degree, while higher entanglement degree in melt-mixed sample leads to a confined segmental dynamics and consequently a slower kinetics (decomposition rate) dominated by macromolecular diffusion at a comparable quench depth. These results reveal that the chain packing in polymer blends can remarkably influence the liquid-liquid phase separation behavior, which is a significant difference from decomposition of small molecular mixtures.

Critical formation conditions for β-form hybrid shish-kebab and its structural analysis

Critical formation conditions for β-form hybrid shish kebab and its unique condensed state structure.

Model Analysis of Rheological Properties of Special Self-Compacting Concrete Paste for High-Speed Railway

The rheological properties of special self-compacting concrete paste played a major role on its performance. The Brookfield R/S SST2000 soft solid tester and TAM AIR 8 channel isothermal calorimeter were used to test the rheological properties and hydration heat effect of special self-compacting concrete paste. The initial cement hydration-rheological model was proposed through the systematical experiments with different water-cement ratio and the chemical admixture, combined with the heat of hydration model of Portland cement. The results showed that the hydration-rheological model of cement paste acted as N, according to the two mutation points on the stress-time curve, which could be divided into three stages, i.e. suspension with no structure, flocculation state structure, condensed state structure. To extend structure mutation values corresponding to the point in time, it can improve the rheological properties of loses with time. With the increasing of water content, heat of hydration effect shows positive effect, but the mechanical effect is weakened. The adding of the superplasticizer delayed the hydration exothermic rate and initial hydration shear stress mutation process.

Interactions between Planar Grafted Neurofilament Side-Arms

The side-arms of neurofilaments (NFs) have been proposed to be highly disordered, leading to an entropically and electrostatically based repulsion that modulates interfilament spacing. To characterize the behavior of two interacting polymer brushes in a system of this type, we performed molecular dynamics simulations of neurofilament brushes using a four bead reduced amino acid set coarse-grained model. In these simulations, we examined components of the neurofilament brush, NF-L, NF-M, and phosphorylated NF-H (NF-HP), individually. Each protein type was grafted to planar surfaces and simulations were performed for a range of separations of two apposed grafted surfaces. The calculated force-separation curves show the force increases as the reciprocal separation as predicted for polyelectrolyte brushes at high salt. All three systems can be overlapped on a single force-separation curve, which is not expected given the variation in amino acid sequence and charges on the polymers. Examination of structural properties shows scaling behavior in the average brush height, end-to-end distance, and the density interpenetration. Some of this scaling can be understood in terms of treating the NF proteins as effective polyelectrolytes, but some cannot suggesting a distinct polyampholyte behavior. Correlations are found between oppositely charged residues in opposite brushes. However, these correlations are weak in comparison to the strong correlations within each brush. In comparison with recent experimental data that observes condensed and expanded gel states, our results suggest that the condensed state structure involves significant interdigitation of the side-arms.