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Molecular dynamics simulations of a small redox-active protein plastocyanin address two questions. (i) Do protein electrostatics equilibrate to the Gibbsian ensemble? (ii) Do the electrostatic potential and electric field inside proteins follow the Gaussian distribution? The statistics of electrostatic potential and electric field are probed by applying small charge and dipole perturbations to different sites within the protein. Nonergodic (non-Gibbsian) sampling is detectable through violations of exact statistical rules constraining the first and second statistical moments (fluctuation–dissipation relations) and the linear relation between free-energy surfaces of the collective coordinate representing the Hamiltonian electrostatic perturbation. We find weakly nonergodic statistics of the electrostatic potential (simulation time of 0.4–1.0 μs) and non-Gibbsian and non-Gaussian statistics of the electric field. A small dipolar perturbation of the protein results in structural instabilities of the protein–water interface and multi-modal distributions of the Hamiltonian energy gap. The variance of the electrostatic potential passes through a crossover at the glass transition temperature Ttr ≃ 170 K. The dipolar susceptibility, reflecting the variance of the electric field inside the protein, strongly increases, with lowering temperature, followed by a sharp drop at Ttr. The linear relation between free-energy surfaces can be directly tested by combining absorption and emission spectra of optical dyes. It was found that the statistics of the electrostatic potential perturbation are nearly Gibbsian/Gaussian, with little deviations from the prescribed statistical rules. On the contrary, the (nonergodic) statistics of dipolar perturbations are strongly non-Gibbsian/non-Gaussian due to structural instabilities of the protein hydration shell. [ABSTRACT FROM AUTHOR]

Lithium-ion conducting borate glasses are suitable for solid-state batteries as an interfacial material between a crystalline electrolyte and an electrode, thanks to their superior formability. Chlorine has been known to improve the electron conductivity of borate glasses as a secondary anion. To examine the impact of chlorine on lithium dynamics, molecular dynamics (MD) simulations were performed with a machine-learning interatomic potential (MLIP). The accuracy of the MLIP in modeling chlorine-doped lithium borate (LBCl) and borosilicate (LBSCl) glasses was verified by comparing with available experimental data on density, neutron diffraction S(q), and glass transition temperatures (Tg). While the MLIP-MD simulations underestimated the density when an isobaric–isothermal (NPT) ensemble was used, the glass models relaxed using the NPT ensemble after a melt-quench simulation employing a canonical (NVT) ensemble possessed reasonable density. The LBCl and LBSCl glass models exhibited increased lithium ion diffusion, and the ions were found to travel longer distances with an increase in the chlorine content. According to the structural analyses, it was observed that chlorine ions primarily interacted with lithium ions rather than the network formers. Consequently, lithium ions that interacted with a higher amount of chlorine showed a moderate increase in mobility. In summary, the MLIP demonstrated reasonable accuracy in modeling chlorine-containing borate glasses and enabled the investigation of the effect of chlorine on electron conductivity. In contrast, the first sharp diffraction peaks in S(q) deviated from the experimental diffractions, suggesting that additional efforts are required to accurately model the middle-range structure of the glasses. [ABSTRACT FROM AUTHOR]

Rolling friction is of great importance for many applications, such as tires and conveyor belts. We study the rolling friction for hard cylinders rolling on flat rubber sheets. The rolling friction depends on the number of rolling cycles, the rolling speed, and the temperature. We show that when the rubber is cooled down below the glass transition temperature, the deformations of the rubber surface are frozen-in, resulting in a non-flat rolling track where uphill and downhill rolling movements strongly affect the rolling force. The experimental data are analyzed using the Persson rolling friction theory; good agreement with the experiments is obtained when the non-linear (strain-softening) properties of the viscoelastic modulus are taken into account. [ABSTRACT FROM AUTHOR]

This work studies the influence of the adsorbed layer on the glass transition of thin films of polysulfone. Therefore, the growth kinetics of the irreversibly adsorbed layer of polysulfone on silicon substrates was first investigated using the solvent leaching approach, and the thickness of the remaining layer was measured with atomic force microscopy. Annealing conditions before leaching were varied in temperature and time (0–336 h). The growth kinetics showed three distinct regions: a pre-growth step where it was assumed that phenyl rings align parallel to the substrate at the shortest annealing times, a linear growth region, and a crossover from linear to logarithmic growth observed at higher temperatures for the longest annealing times. No signs of desorption were observed, pointing to the formation of a strongly adsorbed layer. Second, the glass transition of thin polysulfone films was studied in dependence on the film thickness using spectroscopic ellipsometry. Three annealing conditions were compared: two with only a tightly bound layer formed in the linear growth regime and one with both tightly bound and loosely adsorbed layers formed in the logarithmic growth regime. The onset thickness and increase in the glass transition temperature increases with annealing time and temperature. These differences were attributed to the distinct conformations of the formed adsorbed layers. [ABSTRACT FROM AUTHOR]

Strong changes in bulk properties, such as modulus and viscosity, are observed near the glass transition temperature, Tg, of amorphous materials. For more than a century, intense efforts have been made to define a microscopic origin for these macroscopic changes in properties. Using transition state theory (TST), we delve into the atomic/molecular level picture of how microscopic localized unit relaxations, or "cage rattles," evolve to macroscopic structural relaxations above Tg. Unit motion is broken down into two populations: (1) simultaneous rearrangement occurs among a critical number of units, nα, which ranges from 1 to 4, allowing a systematic classification of glass formers, GFs, that is compared to fragility; and (2) near Tg, adjacent units provide additional free volume for rearrangement, not simultaneously, but within the "primitive" lifetime, τ1, of one unit rattling in its cage. Relaxation maps illustrate how Johari–Goldstein β-relaxations stem from the rattle of nα units. We analyzed a wide variety of glassy materials and materials with a glassy response using literature data. Our four-parameter equation fits "strong" and "weak" GFs over the entire range of temperatures and also extends to other glassy systems, such as ion-transporting polymers and ferroelectric relaxors. The role of activation entropy in boosting preexponential factors to high "unphysical" apparent frequencies is discussed. Enthalpy–entropy compensation is clearly illustrated using the TST approach. [ABSTRACT FROM AUTHOR]

In many fields, from semiconductors for opto-electronic applications to ionic liquids (ILs) for separations, the glass transition temperature (Tg) of a material is a useful gauge for its potential use in practical settings. As a result, there is a great deal of interest in predicting Tg using molecular simulations. However, the uncertainty and variation in the trend shift method, a common approach in simulations to predict Tg, can be high. This is due to the need for human intervention in defining a fitting range for linear fits of density with temperature assumed for the liquid and glass phases across the simulated cooling. The definition of such fitting ranges then defines the estimate for the Tg as the intersection of linear fits. We eliminate this need for human intervention by leveraging the Shapiro–Wilk normality test and proposing an algorithm to define the fitting ranges and, consequently, Tg. Through this integration, we incorporate into our automated methodology that residuals must be normally distributed around zero for any fit, a requirement that must be met for any regression problem. Consequently, fitting ranges for realizing linear fits for each phase are statistically defined rather than visually inferred, obtaining an estimate for Tg without any human intervention. The method is also capable of finding multiple linear regimes across density vs temperature curves. We compare the predictions of our proposed method across multiple IL and semiconductor molecular dynamics simulation results from the literature and compare other proposed methods for automatically detecting Tg from density–temperature data. We believe that our proposed method would allow for more consistent predictions of Tg. We make this methodology available and open source through GitHub. [ABSTRACT FROM AUTHOR]

In experimental and theoretical studies of glass transition phenomena, one often finds a sharp crossover in dynamical properties at a temperature Tcr. A bifurcation of a relaxation spectrum is also observed at a temperature TB ≈ Tcr; both lie significantly above the glass transition temperature. In order to better understand these phenomena, we introduce a new model of glass-forming liquids, a binary mixture of prolate and oblate ellipsoids. This model system exhibits sharp thermodynamic and dynamic anomalies, such as the specific heat jump during heating and a sharp variation in the thermal expansion coefficient around a temperature identified as the glass transition temperature, Tg. The same temperature is obtained from the fit of the calculated relaxation times to the Vogel–Fulcher–Tammann (VFT) form. As the temperature is lowered, the calculated single peak rotational relaxation spectrum splits into two peaks at TB above the estimated Tg. Similar bifurcation is also observed in the distribution of short-to-intermediate time translational diffusion. Interrogation of the two peaks reveals a lower extent of dynamic heterogeneity in the population of the faster mode. We observe an unexpected appearance of a sharp peak in the product of rotational relaxation time τ2 and diffusion constant D at a temperature Tcr, close to TB, but above the glass transition temperature. Additionally, we coarse-grain the system into cubic boxes, each containing, on average, ∼62 particles, to study the average dynamical properties. Clear evidence of large-scale sudden changes in the diffusion coefficient and rotational correlation time signals first-order transitions between low and high-mobility domains. [ABSTRACT FROM AUTHOR]

It is highly demanded to understand the confinement effect on nanoconfined polymers. Recent studies reported a strong perturbation of local dynamics and substantial alteration of glass transition temperature Tg at nanoscale. However, how confinement affects the mechanical properties of polymers is not fully understood. Here, we show that the modulus of thin polymer films could be remarkedly altered through a polymer–polymer interface. The modulus of a thin polystyrene (PS) film next to a polydimethylsiloxane (PDMS) was determined from the PS–PDMS bilayer bulging test. A series of experiments show that the modulus of PS can be increased up to 37%, when the modulus of the neighboring PDMS varies from 1.04 to 4.88 MPa. The results demonstrate a strong sensitivity of mechanical properties of thin polymers to the hard/soft environment, which we attribute to the change of high-mobility layer by the polymer–polymer interface. [ABSTRACT FROM AUTHOR]

Metallic glasses (MGs) are of high strength but limited plasticity at room temperature (RT) due to localized shear in the intrinsically heterogeneous structure. Here, we investigate the variation of structural heterogeneity and plasticity of a Zr-based MG after high-temperature (T) tension under different stresses (σ) at 579 K (0.9Tg, where Tg is the glass transition temperature). The correlation length (ξ) of the heterogeneous structure and the average Young's modulus ( E ¯ ) increase with σ when σ is below 160 MPa; when σ exceeds 160 MPa, both ξ and E ¯ decrease with σ, leading to the improvement of the plasticity. This research could be enlightening for improving the plasticity of MGs at RT through tuning their structural heterogeneity with high-T deformation. [ABSTRACT FROM AUTHOR]

This study investigated the segmental dynamics of polymers near polymer–polymer interfaces by probing the rotation of polymer-tethered fluorescent molecules using imaging rotational fluorescence correlation microscopy. Multilayered films were utilized to provide spatial selectivity relative to different polymer–polymer interfaces. In the experimental setup, for the overlayer polymer, polystyrene (PS) was employed and a 15 nm-thick probe-containing layer was placed ≈25 nm apart from different underlayer polymers with glass transition temperatures (Tg) either lower or higher than that of PS. The underlayer of poly-n-butyl methacrylate had 72 K lower Tg than that of PS, whereas polymethyl methacrylate and polysulfone had 22 and 81 K higher Tg, respectively, than that of PS. Two key dynamic features of the glass transition, the non-Arrhenius temperature dependence and stretched relaxation, were examined to study the influence of soft and hard confinements on the segmental dynamics of the overlayer polymer near the polymer–polymer interfaces. Although complications exist in the probing location owing to the diffusion of the polymer-tethered probe during the annealing protocol to consolidate the multilayers, the results suggest that either the segmental dynamics of the polymer near the polymer–polymer interface do not change owing to the soft and hard confinements or the interfacial perturbation is very short ranged. [ABSTRACT FROM AUTHOR]

In order to prepare highly heat-resistant packaging insulation materials, in this paper, bismaleimide/epoxy resin (BMI/EP55) composites with different contents of BMI were prepared by melt blending BMI into amino tetrafunctional and phenolic epoxy resin (at a ratio of 5:5). The microstructures and thermal and electrical properties of the composites were tested. The electrostatic potential distribution, energy level distribution, and molecular orbitals of BMI were calculated using Gaussian. The results showed that the carbonyl group in BMI is highly electronegative, implying that the carbonyl group has a strong electron trapping ability. The thermal decomposition temperature of the composites gradually increased with the increase of BMI content, and the 20% BMI/EP55 composites had the highest heat-resistance index, along with a glass transition temperature (Tg) of >250 °C. At different test temperatures, with increase in the BMI content, the conductivity of epoxy resin composites showed a tendency to first decrease and then increase, the breakdown field strength showed a tendency to first increase and then decrease, and the dielectric constant was gradually decreased. Two trap centers were present simultaneously in the composites, where the shallow trap energy level is the deepest in 20% BMI/EP composites and the deep trap energy level is the deepest in 10% BMI/EP55 composites. Correspondingly, the 10% BMI/EP55 composite had a slower charge decay rate, while the 20% BMI/EP55 had a faster charge decay rate. In summary, the BMI/EP55 composites with high heat resistance and insulating properties were prepared in this study, which provided ideas for preparing high-temperature packaging insulating materials. [ABSTRACT FROM AUTHOR]

To develop special insulating paper is of great significance to promote the service life of transformers. Using molecular simulation to guide the development of special insulating paper can greatly reduce the trial-and-error rate and waste of resources in traditional experiments. The effect of different types of polysilsesquioxane (POSS) on cellulose insulating paper was investigated by using molecular simulation. This paper investigated the thermal stability and mechanical properties and electrical characteristics of caged POSS, semi-caged POSS, and ladder-like POSS doped cellulose insulating paper. The results show that POSS with all types can enhance the performance of cellulose insulating paper, and ladder-like POSS possess the best modification effect. The glass transition temperature was increased by 58 K, and the bulk modulus, shear modulus, and elastic modulus of cellulose insulating paper doped with ladder-like POSS can improve up to 27.07%, 45.67%, and 41.28%, respectively. Meanwhile, the dielectric properties of ladder-like POSS modified insulating paper are also significantly improved. The findings of this paper propose a method for the preparation of ladder-like POSS modified insulating paper, which provides theoretical guidance for the experimental preparation of special insulating paper. [ABSTRACT FROM AUTHOR]

The present work describes the preparation of a new series of chalcogenide glasses in an As14Sb26S(60−x) (AgI)x system intending to explore its thermal, structural, optical, mechanical, and electrical properties. The differential scanning calorimetry results of the studied glasses show the sharp decrease in glass transition temperature (Tg) with the successive incremental inclusion of AgI in the composition, implying the structural changes in the glass network. A thorough Raman analysis corroborates the occurrence of changes in the glass network due to the formation of AsI3 units and Ag–S–As bonds with increasing AgI content. Also, structural changes can be reflected with the change in the optical bandgap (Eg) that was calculated using Tauc equations where it was found that Eg is in harmony with the observed structural variations of glasses. The studied glasses possess a transmittance window (∼0.68–12 μm) with transmittance above 60% in the mid-infrared region. These structural changes are closely related to the significant enhancement of conductivity of the present glasses from 10−8 to 10−6 S/cm at 373 K with a decrease in activation energies. Impedance spectra for the glass with highest AgI revealed the presence of two different relaxation processes. AC conductivity data followed an Arrhenius behavior as well as Jonscher's power law. The present work provides insights into glass network modifications due to silver iodide inclusion and its role in the enhancement of conductivity. [ABSTRACT FROM AUTHOR]

The impact of successive replacement of K+ by Na+ on the megahertz–gigahertz polarization response of 0.25[fKSCN + (1 − f)NaSCN] + 0.75CH3CONH2 deep eutectic solvents (DESs) was explored via temperature-dependent (303 ≤ T/K ≤ 343) dielectric relaxation (DR) measurements and computer simulations. Both the DR measurements (0.2 ≤ ν/GHz ≤ 50) and the simulations revealed multi-Debye relaxations accompanied by a decrease in the solution static dielectric constant (ɛs) upon the replacement of K+ by Na+. Accurate measurements of the DR response of DESs below 100 MHz were limited by the well-known one-over-frequency divergence for conducting solutions. This problem was tackled in simulations by removing the zero frequency contributions arising from the ion current to the total simulated DR response. The temperature-dependent measurements revealed a much stronger viscosity decoupling of DR times for Na+-containing DES than for the corresponding K+ system. The differential scanning calorimetry measurements indicated a higher glass transition temperature for Na+-DES (∼220 K) than K+-DES (∼200 K), implying more fragility and cooperativity for the former (Na+-DES) than the latter. The computer simulations revealed a gradual decrease in the average number of H bonds (⟨nHB⟩) per acetamide molecule and increased frustrations in the average orientational order upon the replacement of K+ by Na+. Both the measured and simulated ɛs values were found to decrease linearly with ⟨nHB⟩. Decompositions of the simulated DR spectra revealed that the cation-dependent cross interaction (dipole-ion) term contributes negligibly to ɛs and appears in the terahertz regime. Finally, the simulated collective single-particle reorientational relaxations and the structural H-bond fluctuation dynamics revealed the microscopic origin of the cation identity dependence shown by the measured DR relaxation times. [ABSTRACT FROM AUTHOR]

Glutaronitrile (GN) doped with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) at concentrations below and above the room-temperature conductivity optimum near 1M of Li salt is investigated using dielectric spectroscopy and shear rheology. The experiments are carried out from ambient down to the glass transition temperature Tg, which increases considerably as LiTFSI is admixed to GN. As the temperature is lowered, the conductivity optimum shifts to lower salt concentrations, while the power-law exponents connecting resistivity and molecular reorientation time remain smallest for the 1M composition. By contrast, the rheologically detected time constants, as well as those obtained using dielectric spectroscopy, increase monotonically with increasing Li salt concentration for all temperatures. It is demonstrated that the shear mechanical measurements are, nevertheless, sensitive to the 1M conductivity optimum, thus elucidating the interplay of the dinitrile matrix with the mobile species. The data for the Li doped GN and other nitrile solvents all follow about the same Walden line, in harmony with their highly conductive character. The composition dependent relation between the ionic and the reorientational dynamics is also elucidated. [ABSTRACT FROM AUTHOR]

We extend the force-level elastically collective nonlinear Langevin equation theory to treat the spatial gradients of the alpha relaxation time and glass transition temperature, and the corresponding film-averaged quantities, to the geometrically asymmetric case of finite thickness supported films with variable fluid–substrate coupling. The latter typically nonuniversally slows down motion near the solid–liquid interface as modeled via modification of the surface dynamic free energy caging constraints that are spatially transferred into the film and which compete with the accelerated relaxation gradient induced by the vapor interface. Quantitative applications to the foundational hard sphere fluid and a polymer melt are presented. The strength of the effective fluid–substrate coupling has very large consequences for the dynamical gradients and film-averaged quantities in a film thickness and thermodynamic state dependent manner. The interference of the dynamical gradients of opposite nature emanating from the vapor and solid interfaces is determined, including the conditions for the disappearance of a bulk-like region in the film center. The relative importance of surface-induced modification of local caging vs the generic truncation of the long range collective elastic component of the activation barrier is studied. The conditions for the accuracy and failure of a simple superposition approximation for dynamical gradients in thin films are also determined. The emergence of near substrate dead layers, large gradient effects on film-averaged response functions, and a weak non-monotonic evolution of dynamic gradients in thick and cold films are briefly discussed. The connection of our theoretical results to simulations and experiments is briefly discussed, as is the extension to treat more complex glass-forming systems under nanoconfinement. [ABSTRACT FROM AUTHOR]

The glass formation and the dipolar reorientational motions in deep eutectic solvents (DESs) are frequently overlooked, despite their crucial role in defining the room-temperature physiochemical properties. To understand the effects of these dynamics on the ionic conductivity and their relation to the mechanical properties of the DES, we conducted broadband dielectric and rheological spectroscopy over a wide temperature range on three well-established carboxylic acid-based natural DESs. These are the eutectic mixtures of choline chloride with oxalic acid (oxaline), malonic acid (maline), and phenylacetic acid (phenylaceline). In all three DESs, we observe signs of a glass transition in the temperature dependence of their dipolar reorientational and structural dynamics, as well as varying degrees of motional decoupling between the different observed dynamics. Maline and oxaline display a breaking of the Walden rule near the glass-transition temperature, while the relation between the dc conductivity and dipolar relaxation time in both maline and phenylaceline is best described by a power law. The glass-forming properties of the investigated systems not only govern the orientational dipolar motions and rheological properties, which are of interest from a fundamental point of view, but they also affect the dc conductivity, even at room temperature, which is of high technical relevance. [ABSTRACT FROM AUTHOR]

In this work, we propose a linear machine learning force matching approach that can directly extract pair atomic interactions from ab initio calculations in amorphous structures. The local feature representation is specifically chosen to make the linear weights a force field as a force/potential function of the atom pair distance. Consequently, this set of functions is the closest representation of the ab initio forces, given the two-body approximation and finite scanning in the configurational space. We validate this approach in amorphous silica. Potentials in the new force field (consisting of tabulated Si–Si, Si–O, and O–O potentials) are significantly different than existing potentials that are commonly used for silica, even though all of them produce the tetrahedral network structure and roughly similar glass properties. This suggests that the commonly used classical force fields do not offer fundamentally accurate representations of the atomic interaction in silica. The new force field furthermore produces a lower glass transition temperature (Tg ∼ 1800 K) and a positive liquid thermal expansion coefficient, suggesting the extraordinarily high Tg and negative liquid thermal expansion of simulated silica could be artifacts of previously developed classical potentials. Overall, the proposed approach provides a fundamental yet intuitive way to evaluate two-body potentials against ab initio calculations, thereby offering an efficient way to guide the development of classical force fields. [ABSTRACT FROM AUTHOR]

Nanoconfined poly(4-methylstyrene) [P(4-MS)] films exhibit reductions in glass transition temperature (Tg) relative to bulk Tg (Tg,bulk). Ellipsometry reveals that 15-nm-thick P(4-MS) films supported on silicon exhibit Tg − Tg,bulk = − 15 °C. P(4-MS) films also exhibit fragility-confinement effects; fragility decreases ∼60% in going from bulk to a 20-nm-thick film. Previous research found that incorporating 2–6 mol % 2-ethylhexyl acrylate (EHA) comonomer in styrene-based random copolymers eliminates Tg- and fragility-confinement effects in polystyrene. Here, we demonstrate that incorporating 3 mol % EHA in a 4-MS-based random copolymer, 97/3 P(4-MS/EHA), eliminates the Tg- and fragility-confinement effects. The invariance of fragility with nanoconfinement of 97/3 P(4-MS/EHA) films, hypothesized to originate from the interdigitation of ethylhexyl groups, indicates that the presence of EHA prevents the free surface from perturbing chain packing and the cooperative mobility associated with Tg. This method of eliminating confinement effects is advantageous as it relies on the simplest of polymerization methods and neat copolymer only slightly altered in composition from homopolymer. We also investigated whether we could eliminate the Tg-confinement effect with low levels of 2-ethylhexyl methacrylate (EHMA) in 4-MS-based or styrene-based copolymers. Although EHMA is structurally nearly identical to EHA, 4-MS-based and styrene-based copolymers incorporating 4 mol % EHMA exhibit Tg-confinement effects similar to P(4-MS) and polystyrene. These results support the special character of EHA in eliminating confinement effects originating at free surfaces. [ABSTRACT FROM AUTHOR]

The slow Arrhenius process (SAP) is a dielectric mode connected to thermally activated equilibration mechanisms, allowing for a fast reduction in free energy in liquids and glasses. The SAP, however, is still poorly understood, and so far, this process has mainly been investigated at temperatures above the glass transition. By employing a combination of methods to analyze dielectric measurements under both isochronal and isothermal conditions, we were able to quantitatively reproduce the dielectric response of the SAP of different polymers and to expand the experimental regime over which this process can be observed down to lower temperatures, up to 70 K below the glass transition. Employing thin films of thicknesses varying between 10 and 800 nm, we further verified that the peak shape and activation energy of the SAP of poly(4-bromostyrene) are not sensitive to temperature, nor do they vary upon confinement at the nanoscale level. These observations confirm the preliminary trends reported for other polymers. We find that one single set of parameters—meaning the activation barrier and the pre-exponential factor, respectively, linked to the enthalpic and entropic components of the process—can describe the dynamics of the SAP in both the supercooled liquid and glassy states, in bulk and thin films. These results are discussed in terms of possible molecular origins of the slow Arrhenius process in polymers. [ABSTRACT FROM AUTHOR]

To elucidate the atomistic origin of volume relaxation in soda-lime silicate glass annealed below the glass transition temperature (Tg), the experimental and calculated Raman spectra were compared. By decomposing the calculated Raman spectra into specific groups of atoms, the Raman peaks at 800, 950, 1050, 1100, and 1150 cm−1 were attributed to oxygen and silicon in Si–O–Si, non-bridging oxygen in the Q2 unit, bridging oxygen in low-angle Si–O–Si, non-bridging oxygen in the Q4 unit, and bridging oxygen in high-angle Si–O–Si, respectively. Based on these attributions, we found that by decreasing the fictive temperature by annealing below Tg − 70 K, a homogenization reaction Q2 + Q4 → 2Q3 and an increase in average Si–O–Si angle occurred simultaneously. By molecular dynamics simulation, we clarified how the experimentally demonstrated increase in average Si–O–Si angle contributes to volume shrinkage; increasing Si–O–Si angles can expand the space inside the rings, and Na can be inserted into the ring center. [ABSTRACT FROM AUTHOR]

Polyrotaxanes, which consist of mechanically interlocked bonds with rings threaded onto soft polymer chains, exhibit unique mechanical properties and find applications in diverse fields. In this study, we investigate the anomalous segmental dynamics of supercooled polyrotaxane melts using coarse-grained molecular dynamics simulations. Our simulations reveal that the presence of rings effectively reduces the packing efficiency, resulting in well-contained local motion even below the glass transition temperature. We also observe variations in dynamical free volume, characterized by the Debye–Waller factor, which shows a minimum at a ring coverage of 0.1 on threading chains. Such a non-monotonic dependence on coverage shows great consistency in structural relaxation time and dynamic heterogeneity. Specifically, the high segmental mobility of threading linear chains at large coverage can be attributed to the increased dynamical free volume due to supported rigid rings. However, such anomalous segmental dynamics is limited to length scales smaller than one ring size. Beyond this characteristic length scale, the diffusion is dominated by topological constraints, which significantly reduce the mobility of polyrotaxanes and enhance the dynamic heterogeneity. These findings offer microscopic insights into the unique packing structures and anomalous segmental dynamics of supercooled polyrotaxane melts, facilitating the design of advanced materials based on mechanical interlocking polymers for various applications. [ABSTRACT FROM AUTHOR]

The fragility of glass describes how rapidly its molecules slow down as it is cooled near its glass transition temperature. In nanoscale films, polymer glasses with higher fragility experience larger reductions in their Tg compared to those with lower fragility. We investigated whether this is due to the free surface of the polymers, which can cause the surface Tg (Tgsurf) to decrease relative to the bulk Tg. By measuring Tgsurf of various polymers, we found that the shift in Tgsurf relative to the bulk Tg increased with fragility. This suggests that more fragile polymers are more susceptible to the free surface effect. We explain this using the concept of energy landscape, as it is used to explain the different slowdown rates between strong and fragile glass formers at Tg. [ABSTRACT FROM AUTHOR]

Using phase-field simulations, we investigate the bulk coarsening dynamics of ternary polymer solutions undergoing a glass transition for two models of phase separation: diffusion only and with hydrodynamics. The glass transition is incorporated in both models by imposing mobility and viscosity contrasts between the polymer-rich and polymer-poor phases of the evolving microstructure. For microstructures composed of polymer-poor clusters in a polymer-rich matrix, the mobility and viscosity contrasts significantly hinder coarsening, effectively leading to structural arrest. For microstructures composed of polymer-rich clusters in a polymer-poor matrix, the mobility and viscosity contrasts do not impede domain growth; rather, they change the transient concentration of the polymer-rich phase, altering the shape of the discrete domains. This effect introduces several complexities to the coarsening process, including percolation inversion of the polymer-rich and polymer-poor phases—a phenomenon normally attributed to viscoelastic phase separation. [ABSTRACT FROM AUTHOR]

Physical vapor deposition (PVD) provides a route to prepare highly stable and anisotropic organic glasses that are utilized in multi-layer structures such as organic light-emitting devices. While previous work has demonstrated that anisotropic glasses with uniaxial symmetry can be prepared by PVD, here, we prepare biaxially aligned glasses in which molecular orientation has a preferred in-plane direction. With the collective effect of the surface equilibration mechanism and template growth on an aligned substrate, macroscopic biaxial alignment is achieved in depositions as much as 180 K below the clearing point TLC−iso (and 50 K below the glass transition temperature Tg) with single-component disk-like (phenanthroperylene ester) and rod-like (itraconazole) mesogens. The preparation of biaxially aligned organic semiconductors adds a new dimension of structural control for vapor-deposited glasses and may enable polarized emission and in-plane control of charge mobility. [ABSTRACT FROM AUTHOR]

Glass-forming liquids exhibit long-lived, spatially correlated dynamical heterogeneity, in which some nm-scale regions in the fluid relax more slowly than others. In the nanoscale vicinity of an interface, glass-formers also exhibit the emergence of massive interfacial gradients in glass transition temperature Tg and relaxation time τ. Both of these forms of heterogeneity have a major impact on material properties. Nevertheless, their interplay has remained poorly understood. Here, we employ molecular dynamics simulations of polymer thin films in the isoconfigurational ensemble in order to probe how bulk dynamic heterogeneity alters and is altered by the large gradient in dynamics at the surface of a glass-forming liquid. Results indicate that the τ spectrum at the surface is broader than in the bulk despite being shifted to shorter times, and yet it is less spatially correlated. This is distinct from the bulk, where the τ distribution becomes broader and more spatially organized as the mean τ increases. We also find that surface gradients in slow dynamics extend further into the film than those in fast dynamics—a result with implications for how distinct properties are perturbed near an interface. None of these features track locally with changes in the heterogeneity of caging scale, emphasizing the local disconnect between these quantities near interfaces. These results are at odds with conceptions of the surface as reflecting simply a higher "rheological temperature" than the bulk, instead pointing to a complex interplay between bulk dynamic heterogeneity and spatially organized dynamical gradients at interfaces in glass-forming liquids. [ABSTRACT FROM AUTHOR]

Sr2CoRuO6 in its bulk form shows spin glass behavior with a transition temperature of 95 K, and in its epitaxial thin film, it shows similar behavior with a transition temperature of 135 K. We have studied the structural, electronic, and magnetic properties of a polycrystalline thin film of oxygen-deficient Sr2CoRuO6−δ (SCRO), which shows ferrimagnetic or glassy behavior up to room temperature. The presence of oxygen deficiency causes multivalent cations Co3+ and Co2+ and Ru4+ and Ru5+, which introduces various kinds of magnetic interactions between Co3+–O–Co2+, Co3+–O–Ru4+, Co2+–O–Ru4+, Co3+–O–Ru5+, and Co2+–O–Ru5+ exchange paths, producing unusual exchange bias effects in the single layer thin film of SCRO. The interionic charge transfer between Co and Ru ions as a result of the negative charge transfer energy of the system helps in visualizing the unconventional exchange bias effect in the system. [ABSTRACT FROM AUTHOR]

Physical aging is the process of a system evolving toward a new equilibrium, and thus the response to a change in external parameters such as temperature T, pressure p, or static electric field E. Using a static electric field has been shown to access physical aging above the glass transition temperature Tg, in the regime of milliseconds or faster, but the relation to its temperature jump counterpart has not been investigated to date. This work compares temperature and field induced physical aging in the limit of small perturbations for supercooled tributyl phosphate. It is found that both structural recovery dynamics are very similar, and that they match the collective reorientational dynamics as observed by dielectric relaxation. The results facilitate expanding the range of aging experiments to well above Tg, where a comparison with structural relaxation in equilibrium is straightforward, thus improving models of structural recovery and physical aging. [ABSTRACT FROM AUTHOR]

This study presents a detailed investigation into the structural, thermal, and radiation shielding properties of a new glass composition, labeled as (50-x)B 2 O 3 + 30TeO 2 + 10Bi 2 O 3 + 10CdO + x Tm 2 O 3 (where x = 0, 1, 2, 3, 4, 5 mol %). Various radiation shielding parameters such as mass attenuation coefficient, linear attenuation coefficient, half-value layer, mean free path, effective atomic number, and absorbed equivalent dose rates for neutrons were determined through experimental measurements. The study also employed theoretical calculations to assess the exposure buildup factor and effective removal cross-section for neutrons. Additionally, the SRIM program was utilized to investigate mass stopping power and projected range for proton and alpha particles. The structural characteristics of the glasses were analyzed using XRD and FT-IR, while thermal properties were examined through Differential Thermal Analysis (DTA). FTIR analysis revealed distinctive bands corresponding to Bi—O, B—O—B, and Te—O bonds. Glass transition temperatures (T g) increased with Tm 2 O 3 content, ranging from 422 °C to 444 °C. The radiation shielding properties of bismuth boro-tellurite glasses showed that a dose of 1.2025 μSv/h emitted from a fast neutron source was absorbed by 35.1574 % in pure glass and 40.0391 % in glass doped with 5 mol% Tm 2 O 3. Incorporating Tm 2 O 3 into the glass matrix significantly improved the shielding and thermal properties, thus enhancing their potential for advanced high-energy radiation absorption. This investigation contributes to a deeper understanding of how Tm 2 O 3 enhances the structural and thermal attributes of these glasses, positioning them as promising materials for radiation shielding applications. [ABSTRACT FROM AUTHOR]

A series of 14R 2 O/MO-5ZnO-3Al 2 O 3 -40TiO 2 -38P 2 O 5 (R=Li, Na, K; M = Mg, Ca, Sr) glasses were synthesized using the traditional melt-quenching method, and controlled crystallization was used to produce glass-ceramics. The results indicate that the glass transition temperature and crystallization temperature increase when the ion radius increases within the same main group. The hardness of titanium phosphate glass shows a non-linear dependence on the cation field strength, and the highest value is obtained in the glass containing Li+ and Sr2+. The major crystalline phase of the glass-ceramics is RTi 2 (PO 4) 3 /M 0.5 Ti 2 (PO 4) 3 with NASICON structure. The crystal size and cell parameters are positively correlated with the radius of cations. The glass-ceramic containing the major crystalline phase Mg 0.5 Ti 2 (PO 4) 3 crystalline phase exhibits the lowest band gap and the best photocatalytic activity, with a dye degradation rate of 68 % at 120 min, and a reaction rate of 9.24 × 10−3 min−1 is about 5 times higher than that of the same series of low-activity samples. [ABSTRACT FROM AUTHOR]

The use of graded-index (GRIN) lenses in infrared imaging systems is an effective way to reduce system volume. Chalcogenide glass has been considered an ideal matrix material to produce infrared GRIN lenes because of its excellent rheological property and large refractive index (RI) tunability. Herein, an axial GRIN Ge-As-Se-Te chalcogenide glass with large RI contrast (Δn) was designed and prepared. The GRIN glass was obtained by hot-pressing 11 stacked glass disks with gradually changing RIs and thermally treating them. The glass compositions of the disks were designed according to (1-x) (Ge 20 As 20 Se 20 Te 40)-xGe 12 As 22 Se 66 , where x = 0–1. It was found that these glasses had similar glass transition temperatures of 194∼199 °C, and excellent anti-crystallization performance. The RI (at 10 μm) of the glass dropped approximately linearly from 3.050 to 2.566 as x increased from 0 to 1. More than 1.2 mm diffusion depth was observed on hot-pressed two-layer glass preforms after only 24-h heat treatment. A GRIN glass with a thickness of ∼4.3 mm and linear RI profile was achieved by treating a hot-pressed eleven-layer glass preform for 24 h. The obtained GRIN glass showed good transmittance in the 3–12 μm wavelength range. These results indicate good prospects of the GRIN Ge-As-Se-Te glass for infrared imaging. [ABSTRACT FROM AUTHOR]

A bio‐based benzoxazine monomer, diphenolic methyl ester hexafluoro diamino benzoxazine (DPME‐HFBz), was successfully synthesized from diphenolic acid (DPA), and the chemical structure was successfully verified. The curing kinetics were studied via non‐isothermal differential scanning calorimetry (DSC). The activation energies of DPME‐HFBz were calculated by Kissinger and Ozawa methods to be 136.15 and 139.92 kJ/mol, respectively, and the reaction order was calculated to be first order. Owing to the large number of hydrogen bonds after polymerization, poly(DPME‐HFBz) presented an ultra‐high glass transition temperature of 312 °C and a high initial decomposition temperature (350 °C under air and 345 °C under nitrogen). Because of the excellent charring ability (50.2% residue under nitrogen), the LOI value of poly(DPME‐HFBz) was as high as 38%. Poly(DPME‐HFBz) also exhibited a very low heat release capacity (HRC) of 90 J/(g·K). In addition, poly(DPME‐HFBz) had a dielectric constant (Dk) of 1.88 at 1.5 MHz, which was much lower than the Dk of the reported low‐dielectric polymers. This work provides an efficient and sustainable strategy for the synthesis of benzoxazine thermosetting materials with excellent comprehensive properties. [ABSTRACT FROM AUTHOR]

The copolymerization of two or more monomers produces polymeric materials with unique properties that cannot be achieved with homopolymers. However, precise control over the polymer sequence remains challenging because the sequence is determined by the inherent reactivity of comonomers. Therefore, only limited methods using modified monomers or supramolecular interactions are reported. In this study, the sequence control of acrylate‐styrene copolymerization using multinuclear zinc complexes is reported. The copolymerization of the zinc acrylate complex with a polymeric sheet‐like structure and styrene in benzene affords a copolymer with a higher content of acrylate triad than calculated for the statistical random model, whereas tetranuclear zinc acrylate (TZA) affords a copolymer with fewer adjacent acrylate sequences. The copolymer with a higher content of acrylate triad exhibits a lower glass transition temperature because of the higher mobility of the longer polystyrene segments. These results highlight the promise of multinuclear zinc acrylate complexes as monomers for sequence‐controlled copolymerization. [ABSTRACT FROM AUTHOR]

Vat photopolymerization (VPP) of highly aromatic polyurethanes (PUs) expands the library of additive manufacturing (AM) materials and enables a vast array of ductile thermoplastics, rigid and flexible thermosets, and elastomers. Aromatic diisocyanates and various diols enable printing of rigid, highly aromatic cross‐linked parts, which offer high glass transition temperatures and tunable thermomechanical performance. The judicious control of molecular weight of the photo‐reactive telechelic oligomers allows for a fundamental study of the influence of cross‐link density in highly aromatic 3D PU printed objects. VPP AM produces objects with high resolution, smooth surface finish, and isotropic mechanical properties. Thermal post‐processing is critical in maintaining excellent thermomechanical properties with semi‐crystallinity as a function of cross‐link density. Due to the presence of two ester carbonyls in the bis(2‐hydroxyethyl) terephthalate chain extender, the printed parts are readily amenable to depolymerization with methanolysis to produce difunctional dimethyl dicarbamates under modest reaction conditions. Dimethyl dicarbamates serve as suitable monomers for subsequent polycondensation. [ABSTRACT FROM AUTHOR]

Highlights To predict the coefficient of thermal expansion (CTE) of carbon fiber/epoxy resin composites with void defects comprehensively and accurately, a comprehensive study is carried out by integrating experiment, analytical model (ANM), and finite element model (FEM). The experiments on composites are conducted combining with Micro‐CT to provide geometric parameters and verification for ANM and FEM. An ANM considering void defects is established based on the Chamis model to investigate the influence of porosity, temperature and the ratio of modulus of the constituents of composites. A FEM is established to verify the ANM and reveal the mechanisms of the influence of void defects. The results show that the proposed ANM has high agreement with FEM and experiment. The longitudinal CTE decreases by 61.94% as the porosity increases from 0% to 20% at 60°C, and the same change of porosity results in a 15.62% decrease at 180°C. The transverse CTE is less susceptible to changes in porosity, showing reductions of 2.32% at 60°C and 3.33% at 180°C. An innovative model is proposed to predict CTE considering void defects. The glass transition temperature Tg of the resin has a significant effect on CTE. Void defects change the homogeneity of the original stress field of the matrix. The reduction of the longitudinal CTE caused by void defects is more significant. [ABSTRACT FROM AUTHOR]

This paper investigated the effect of elevated temperature on the impact‐induced deformation and damage behavior of 3D angle‐interlock woven composites. The transverse impacts were carried out at high temperatures of 90°C and 130°C using Split Hopkinson Pressure Bar matched with controlled environmental device. A meso‐scale finite element model considering the thermal‐mechanical coupling has been developed, and the numerical results were compared with the experimental data and high‐speed photography to study the effect of temperature and reinforcement architecture on the dynamic behaviors of the composites. The damage mechanisms at elevated temperatures were studied. Results show that the impact resistance of the 3D angle‐interlock woven composites degraded at the glassy region of the epoxy resin, then enhanced at the glass transition temperature (Tg), this phenomenon became more pronounced in the warp direction. Such behavior should be ascribed to the improved toughness and ductility of the resin matrix. The local plastic deformation of resin before damage slowed down matrix cracking and composites failure. Further, the reinforcement play a key role in the adiabatic heating and plastic deformation of the composites at high temperature. Highlights: The impact test of 3D woven composites was conducted at elevated temperatures.The high temperature significantly affects the dynamic properties of composites.The increased toughness and plasticization of resin diminished impact damage.A mesoscale thermo‐mechanical coupled finite element model was developed.The reinforcement plays a key role in the damage process and adiabatic heating. [ABSTRACT FROM AUTHOR]

ABSTRACT This study investigated the survival dynamics of Lactobacillus plantarum BG24, a probiotic strain, within reconstituted skim milk (RSM) and yeast extract (YE) matrices during the spray–drying (SD) process, encompassing of inlet/outlet air temperatures. Notably, optimum SD parameters were found to be an inlet air temperature of 150°C and outlet air temperature of 83°C, that achieving high viability (92.23%), and reducing both moisture content (MC) (3.57%) and water activity (aw) (0.266). The use of soy protein isolate (SPI), gum Arabic (GA), RSM, maltodextrin (MD), sucrose (SUC), and lactose in binary mixtures or alone was investigated in terms of the best survival rate of probiotic bacteria, and RSM alone and RSM + GA and SPI alone were found to be the best drying carriers giving higher viability during SD. SD at optimum process temperatures and freeze drying (FD) were compared in the survival rate of probiotic bacteria in the carrier of RSM with YE, and FD samples showed a higher survival rate (97.69%) than SD samples. It was determined that the storage temperature (4°C and 20°C) had an impact on the glass transition temperature, MC, aw, and cell viability. Increased storage temperature led to a greater decrease in cell viability, especially for SD probiotic powders. These findings furnish critical insights into the intricate interplay among process parameters, carrier agents, drying techniques, and storage conditions, thereby elucidating avenues for refining probiotic preservation strategies within the ambit of SD, and by extension, in the domains of food and pharmaceutical sciences. [ABSTRACT FROM AUTHOR]

There is a high demand for highly biobased photocurable coatings for a wide range of applications. In this work, a photocurable coating formulation is developed based on isobornyl acrylate (IBOA) and a biobased polyester diacrylate. Besides, a phosphorous‐containing biobased dimethacrylate resin having imine groups (VDDM) is synthesized. Different ratios of VDDM are added to the biobased base formulation. VDDM is characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopies. The formulations are coated on aluminum substrates and photocured under UV light. The biobased contents of the prepared networks are in the range of ≈68–79%. Coatings display a good adhesion on the aluminum substrates. The incorporation of VDDM into the formulations slightly increases the glass transition temperature values. Moreover, VDDM enhances the hydrophilicity of the coatings. VDDM‐free coatings are found to be resistant to degradation under basic and acidic media, but the presence of imine bonds in VDDM leads to the partial degradation of the prepared networks under acidic aqueous conditions. Finally, it is demonstrated that the coatings prepared herein are resistant to corrosion. The prepared highly biobased networks in this study have the potential to be used as photocurable coil coatings. [ABSTRACT FROM AUTHOR]

Highlights Glass fiber‐reinforced polymer composites are widely used in marine applications, including renewable energy devices and submarines, due to their strength‐to‐weight ratios and corrosion resistance. As sustainability becomes more important, recyclable thermoplastic composites are gaining attention in marine energy applications. These materials face harsh conditions such as high chloride water, UV radiation, pressurization, and thermal cycling, which can affect their durability and recyclability. This study examines the impact of hygrothermal aging on the recyclability of an Elium glass fiber (GF) composite. Samples were mechanically ground for recycling, and mechanical and thermal properties were compared between aged and unaged samples. After seawater aging, the tensile strength and modulus of the unaged composite dropped by 25% and 13% respectively, due to water ingress along the fiber‐matrix interface. The recycled composite showed reduced flexural strength as the long fiber composite was converted into short fibers during the process. Differential scanning calorimetry (DSC) revealed no change in glass transition temperature after aging. Weight loss (25%) was attributed to the thermal stability of the glass fibers. Dynamic mechanical analysis (DMA) showed that the storage modulus increased with aging, and fracture analysis confirmed a mixed mode of failure for aged composites. Hygrothermal aging lowers mechanical performance of Elium® GF composites. Failure mechanism tends to be matrix cracking and interface bonding. Glass transition temperature is not reduced by hygrothermal aging. Fractured composite was successfully recycled via thermoforming. Flexural strength of the recycled composite is lower. [ABSTRACT FROM AUTHOR]

Highlights Thermoplastic PMMA was rarely exploited in continuous fiber‐reinforced composites due to its viscous high‐temperature molten fluid as well as pessimistic wettability into fiber fabric. Redox‐active polymerization is a green route to develop a new liquid PMMA resin at room temperature to provide an in situ curing with the advantages of energy saving and consumption reduction. In this paper, BPO/DMA was adopted as a redox initiator pair, and the effect of MMA:BPO:DMA ratio on curing time, Mn, Tg, and mechanical properties of PMMA were systematically studied. When the ratio of MMA:BPO:DMA is 200:1.2:1, PMMA‐200 achieved optimistic mechanical properties at 20°C (tensile strength, 64.7 MPa; tensile modulus, 3352 MPa; bending strength, 125.3 MPa; bending modulus, 3023 MPa). Moreover, the mechanical properties were further improved at low temperatures. The maximum tensile strength and tensile modulus were up to 97.43 and 4297 MPa (−40°C) respectively. The tensile strength (0°, 1103 MPa; 90°, 52.3 MPa) and tensile modulus (0°, 47.5 GPa; 90°, 14.2 GPa) of glass‐fiber‐reinforced PMMA composite at 20°C were found to be comparable with epoxy resin‐based composites and even higher at lower temperature. In summary, redox‐initiated PMMA and its fiber‐reinforced composites are promising thermoplastic materials as new lightweight alternatives. Preparation method of PMMA resin and glass fiber composite. Research on the mechanical properties, molecular weight, glass transition temperature, curing time, etc. of PMMA resin. Testing of mechanical properties of PMMA glass fiber composites at room temperature and low temperature. Current applications and prospects of PMMA glass fiber composites. [ABSTRACT FROM AUTHOR]

Highlights Hot compression molding was used to produce biocomposites from ramie plain‐woven fabric‐reinforced polylactic acid (PLA). Prior to composite fabrication, alkali and dipodal silane (bis(3‐trimethoxysilylpropyl) amine) (BAS) were applied to improve fiber‐matrix adhesion. Mechanical tests revealed improvements in tensile and flexural strength due to interfacial adhesion. The flexural strength of ramie PLA composite samples treated only with silane (SR‐PLA) was the highest, at 136.35 MPa. Young's modulus was 7.51 GPa. BAS treatment was crucial for ensuring strong adhesion between the fabric and the PLA matrix. In combined alkali‐BAS‐treated composites (ASR‐PLA), the glass transition and crystallization temperatures disappeared completely, affecting PLA morphology. The maximum heat of absorption (373°C) was found in SR‐PLA composites, suggesting electrostatic interactions created a three‐dimensional network. In conclusion, the initial incorporation of dipodal silane resulted in the formation of six silanol linkages with ramie fabric, leading to enhancements in the mechanical and thermal characteristics of ramie–PLA composites. Alkali and BAS treated Fabrics ironed to remove treatment‐induced wrinkles. Carded PLA fiber with consistent density and weighted in four equal portions. Fabric and PLA lay alternatively in warp direction before compression molding. SR‐PLA composites exhibited improved thermal and mechanical properties. [ABSTRACT FROM AUTHOR]

In the present study, low molecular weight cyclic polyglycidol is used as a macroinitiator for hypergrafting glycidol and producing cyclic graft hyperbranched polyglycerol (cPG‐g‐hbPG) in the molecular weight range of 103–106 g mol−1. Linear graft hyperbranched polyglycerol (linPG‐g‐hbPG) and hyperbranched polyglycerol (hbPG) are prepared as reference samples. This creates a family of hbPG structures with cyclic, linear, and star cores, allowing to evaluate their properties in solution and in bulk. The morphology study of the high molecular weight structures using atomic force microscopy revealed a spherical shape for cPG‐g‐hbPG and hbPG, and a cylindrical shape for linPG‐g‐hbPG in the nanometric range. Small angle X‐ray scattering confirmed the compact particle‐like structure of this family of hbPG architectures. Interestingly, the glass transition temperature showed a structure dependence, with cPG‐g‐hbPG having the highest values and hbPG having the lowest values for the same molecular weight. This study is a step forward in the generation of water‐soluble polymers with tailored structure and functionality for advanced applications. [ABSTRACT FROM AUTHOR]

Natural lignocellulosic fibers (NLFs) have shown a great potential as reinforcements in composites in recent decades. Among other reasons, environmental concerns and the depletion of oil reserves justify research on natural composites as they offer an environmentally friendly alternative and align with the principles of sustainable development. Among the plethora of NLFs available in nature, the ubim fiber (Geonoma baculifera) has not yet been investigated as a reinforcement for composites in potential engineering applications. Therefore, this study evaluates, for the first time, the mechanical properties of epoxy composites with 10, 20, and 30 vol% of ubim fibers. These properties were assessed through Izod impact, tensile and flexural tests as well as dynamic mechanical analysis (DMA). The data were statistically analyzed using the ANOVA method. Scanning electron microscopy (SEM) analysis indicated a transition from a purely brittle fracture mechanism to a ductile-brittle combination as the fiber volume in the composite increased. Tensile tests of the composites demonstrated an increasing trend in strength and elastic modulus with fiber volume. The results of the flexural tests also displayed a similar trend in strength and elasticity modulus for the composites. The results of DMA tests showed that composite materials with a 30 vol% of ubim fibers exhibited a high glass transition temperature and a low tan δ value, suggesting higher stiffness of this composite compared to others. Overall, the results indicated that the incorporation of 30 vol% ubim fibers into the composites significantly improved their mechanical properties compared to other tested fiber fractions. Additionally, their functional characteristics, such as simplicity in the manufacturing process, low cost, and excellent strength-to-weight ratio, make these composites particularly suitable for applications in sectors such as the automotive industry, construction panels, and packaging. These factors contribute to the development of an efficient, sustainable, recyclable and environmentally friendly composite. [ABSTRACT FROM AUTHOR]

Water-based coating has gained much attention globally due to environmental issues. This work aims to develop a waterborne epoxy coating incorporated with modified natural rubber (NR) latex for improved performance. For this purpose, the NR latex was modified into three types of low molecular weight epoxidized natural rubber (LENR) latex. The waterborne epoxy resin was prepared by simply mixing the epoxy resin with an amine curing agent in water and various LENR latex contents (10 to 50 wt%). The waterborne epoxy/LENR blend was coated on a tin substrate and the cured coating demonstrated better adhesion and bending properties than the neat epoxy. Phase morphological properties displayed a rough surface with a heterogeneous surface structure of the dispersed rubber and epoxy matrix. Two glass transition temperatures were observed, corresponding to the rubber modifier and the epoxy matrix. The mechanical properties of the thermosetting epoxy/LENR blends were assessed, revealing a maximum increment in elongation ability by approximately 370% for adding 50 wt% LENR, compared to the neat epoxy. These results hold the potential avenue for utilizing NR-based material in the waterborne epoxy-based resin for coating applications. Furthermore, it contributes to the NR, a renewable and eco-friendly material, in the coating technology, embracing a sustainable future. [ABSTRACT FROM AUTHOR]

Type V linerless hydrogen storage vessels made of all-composite face the challenges of cryogenic mechanical failure and hydrogen leakage of composites. The cryogenic mechanical performance and gas-barrier property of the carbon fiber reinforced polymer for Type V vessels are largely determined by the epoxy matrix. Carbon nanotubes are widely used as polymer reinforcement material to enhance the cryogenic mechanical performance and gas-barrier property of epoxy resins. In this work, multi-walled carbon nanotubes (MWCNTs) were dispersed into epoxy resins to prepare MWCNTs-modified epoxy resins. The cryogenic mechanical performance, gas-barrier and thermal properties of the modified resin were then investigated. The experimental findings revealed a 34.34% reduction in the gas permeability coefficient for the nanocomposites containing 0.9 wt% MWCNTs compared with the epoxy matrix. The tensile strength and failure strain at cryogenic temperature (77 K) experienced enhancements of 26.99% and 41.53%, respectively. In addition, the thermal stability and glass transition temperature of the modified resin were improved. As a result, the MWCNTs-modified epoxy resin exhibits improved gas-barrier property in addition to excellent cryogenic mechanical performance, making it ideal for manufacturing Type V linerless hydrogen storage vessels. • The thermal stability and glass transition temperature of the modified resin are improved. • The tensile strength and failure strain at 77 K improved by 26.99% and 41.53%, respectively. • The gas permeability coefficient of MWCNTs-modified resin decreases by 34.34%. • The mechanism of MWCNTs enhancing resin's gas-barrier and mechanical properties is explained. [ABSTRACT FROM AUTHOR]

Ion exchange typically involves replacing smaller ions with larger ions below the glass transition temperature. This study introduces an innovative computational approach for the inverse design of ion-exchangeable glasses. It aims to simultaneously achieve high depth of layer (DOL) and surface compressive stress (CS), a task complicated by the inherent trade-offs between these properties. Traditional ion exchange experimental methods are not only time-consuming and expensive, but they also involve complex practical difficulties. Addressing these challenges, this paper introduces a novel computational approach that synergistically combines a multi-objective genetic algorithm with machine learning models. The approach involves training models on a diverse set of glass compositions to predict DOL and CS, which then guide an evolutionary algorithm to optimize these properties concurrently. Physics-informed parameters further refine the search, enabling a flexible design framework in glass manufacturing. Comprehensive experimentation and subsequent analysis affirm the proposed method's capacity to efficiently and effectively traverse the intricate design landscape of glass materials. The findings elucidated the influence of distinct compositional and process parameters on DOL and CS, facilitating the manual design process. Additionally, the study identified sixteen glass composition candidates within the SiO 2 –B 2 O 3 –Al 2 O 3 –MgO–Na 2 O system, exhibiting remarkable properties. Specifically, some compositions achieved a DOL of up to 95 μm with a corresponding CS of 890 MPa, while others attained a CS of up to 1654 MPa with a DOL of 14.72 μm. [ABSTRACT FROM AUTHOR]

Corn starch‐based direct expanded products incorporated with 2% and 10% (w/w) sugar (fructose, glucose, sucrose, and xylose) were produced using a 20 mm co‐rotating twin‐screw extruder. The pasting and thermal properties of raw corn starch‐sugar mixes were analyzed before extrusion processing. The independent variables for extrusion processing included two sugar inclusion levels (2% and 10% w/w) and two screw speeds (150 and 250 rpm). The extrudates were characterized by their initial expansion ratio (IER), expansion ratio (ER), and shrinkage. ER values were high for fructose at 2% and 150 rpm and 10% glucose and sucrose extrudates at 250 rpm. The extrudates with 2% sucrose inclusion shrunk significantly higher than the control. Fourier transform infrared (FTIR) spectroscopy of the extruded blends did not indicate the presence of any new covalent bond formed between starch and sugar post‐extrusion. The interactions between sugar concentration and screw speed significantly influenced extrudate expansion characteristics. Due to their thermal and plasticizing properties, sugar inclusion (glucose, fructose, sucrose, and xylose) enhanced the extrudate expansion by altering their melt viscosity. Practical Application: The findings of this study can improve the expansion characteristics of high‐fiber‐based extruded snacks. Ingredients high in fiber generally hinder the starch transformation during extrusion and negatively impact the expansion properties. The presence of sugar at low concentrations can improve melt properties during extrusion processing and, in turn, significantly improve the textural properties of snacks. [ABSTRACT FROM AUTHOR]

Fluorinated polyurethaneimide (PUI) electro-optic waveguide polymer with polyurethane and polyimide chain segment structures was synthesized by stepwise polymerization using the synthesized amino ester oligomer pu and imide oligomer pi as monomers. Since the main chain structure of the synthesized PUI had the functionality of both polyurethane and polyimide chain segment structures, it combines the excellent thermal and film-forming properties of polyurethanes and polyimides, as well as lower optical transmission loss in the near-infrared wavelength band. The glass transition temperature (Tg) of PUI was 182 °C, and the 5% heat loss decomposition temperature was 325 °C. The PUI had good optical properties with an optical propagation loss of 1.10 dB/cm and an electro-optic (EO) coefficient (γ33) of 86 pm/V at a wavelength of 1550 nm. A Mach-Zehnder interferometric polymer waveguide EO modulator had been designed and fabricated by using the PUI as a waveguide electro-optic core layer. The prepared polymer waveguide EO modulator showed a good electro-optic modulation response at a wavelength of 1550 nm under an applied 1 kHz sinusoidal modulation signal. The results showed that the synthesized PUI met the performance requirements for the preparation of polymer optical waveguide devices and was a polymer electro-optic waveguide material with good overall performance. [ABSTRACT FROM AUTHOR]

Oligomeric poly(α-methyl-β-alanine)with vinyl end-group (PmBA) was synthesized via base-catalyzed hydrogen-transfer polymerization (HTP) of molten methacrylamide (MAm) in the presence of sodium tert-butoxide (t-BuONa). The PmBA was used as a comonomer in the synthesis of amphiphilic poly(2-hydroxyethyl acrylate-g-α-methyl-β-alanine) (PHEA-g-PmBA)via nitroxide-mediated polymerization (NMP)and "grafting through" approach.The graft copolymer formation was confirmed byproton nuclear magnetic resonancespectroscopy (1H-NMR), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and static light scattering (SLS)measurements. Thermogravimetric analysis of the amphiphilicPHEA-g-PmBAexhibited a multi-step decomposition curve corresponding to the α-methyl-β-alanine and the 2-hydroxyethyl acrylate blocks at about 306, 369, and 403 °C.DSC curve of the copolymer has a baseline shift at −12.87 °C attributed to the glass transition temperature. SLS analysis of the final product resulted in a weight average molecular weight of 83.6 kDa. The spectroscopic and thermal analyses proved that amphiphilicPHEA-g-PmBA was successfully synthesized through HTP and NMP. [ABSTRACT FROM AUTHOR]

Silicon-containing arylacetylene (PSA) resins have broad application prospects because of their excellent heat resistance. However, improving their mechanical properties and interfacial bonding with reinforcement fibers while maintaining heat resistance is a challenge in engineering applications. Here, poly(diethynylbenzene-methylsilyl-3-benzonitrile) (DEB-CN) and poly(diethynylbenzene-methylsilyl-3,6-diethynylcarbazole-3-benzonitrile) (DEC-CN) were synthesized via an isopropylmagnesium chloride lithium-chloride complex (i-PrMgCl·LiCl), overcoming the compatibility problem between cyano groups and Grignard reagents. The cyano and alkyne groups in the resin underwent cyclization to form pyridine, catalyzed by the -NH- moiety in DEC-CN, resulting in extremely high thermal stability (5% weight loss temperature: 669.3 °C, glass transition temperature >650 °C). The combination of cyano dipole-dipole pairing and hydrogen bonding greatly enhanced the resin-fiber interface properties, while the generated pyridine promoted stress relief in the crosslinked network, substantially improving the mechanical properties of the cyano-silicon-containing arylacetylene resin composites. The flexural strength of quartz fiber cloth/DEC-CN composites was 298.2 MPa at room temperature and 145.9 MPa at 500 °C, corresponding to 84.0% and 127.6% enhancements, respectively, over the cyano-free counterpart. These cyano-silicon-containing arylacetylene resins exhibited a dual reinforcement mechanism involving physical interfacial interactions and chemical crosslinking, achieving a good balance between thermal stability and mechanical properties. [ABSTRACT FROM AUTHOR]