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The dynamics of polymer nanocomposites varies depending on the physics and chemistry at the polymer–nanoparticle interface. The physical aging of the nanocomposites is accelerated or retarded based on interfacial interactions and the state of polymer adsorption at the interfaces. In this study, we investigated the aging kinetics of silica–polystyrene nanocomposites using differential scanning calorimetry, focusing on the effect of local conformations of chains adsorbed on the nanofiller surface. The results show that the temperature dependence of the aging rate follows a Vogel–Fulcher–Tammann relationship at high temperatures, whereas it exhibits an Arrhenius-like behavior below a characteristic temperature (Tc). Notably, at T < Tc, the aging rate decreases with increasing loop height of the chains adsorbed on the filler surface, but the activation energy remains unchanged. We proposed that the suppression of the aging rate at T < Tc is likely related to an increase in the length scale over which the slow interfacial dynamics can propagate due to the increased topological interactions between the chain loops of a larger size and the free chains in the matrix. The increased packing frustration occurring at the filler surface occupied by the larger loops might also contribute to the decreased aging rate. [ABSTRACT FROM AUTHOR]

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The introduction of soft organic nanoparticles (NPs) into polymer melts has recently expanded the material design space for polymer nanocomposites, compared to traditional nanocomposites that utilize rigid NPs, such as silica, metallic NPs, and other inorganic NPs. Despite advances in the fabrication and characterization of this new class of materials, the effect of NP stiffness on the polymer structure and dynamics has not been systematically investigated. Here, we use molecular dynamics to investigate the segmental dynamics of the polymer interfacial region of isolated NPs of variable stiffness in a polymer matrix. When the NP–polymer interactions are stronger than the polymer–polymer interactions, we find that the slowing of segmental dynamics in the interfacial region is more pronounced for stiff NPs. In contrast, when the NP–polymer interaction strength is smaller than the matrix interaction, the NP stiffness has relatively little impact on the changes in the polymer interfacial dynamics. We also find that the segmental relaxation time τα of segments in the NP interfacial region changes from values lower than to higher than the bulk material when the NP–polymer interaction strength is increased beyond a "critical" strength, reminiscent of a binding–unbinding transition. Both the NP stiffness and the polymer–surface interaction strength can thus greatly influence the relative segmental relaxation and interfacial mobility in comparison to the bulk material. [ABSTRACT FROM AUTHOR]

X linked hypophosphataemia (XLH) is a systemic, chronic condition that significantly impairs quality of life. In XLH, a phosphate regulating endopeptidase homologue X-linked (PHEX) gene mutation leads to excess fibroblast growth factor 23 (FGF23), causing hypophosphataemia and subsequent rickets, lower limb deformity, pain and other sequelae, however there are likely other non-FGF23 mediated mechanisms contributing to disease. Burosumab is an FGF23 inhibiting monoclonal antibody that has been shown to be significantly more effective in treating X linked hypophosphataemia than previously available treatment ("conventional therapy" with oral phosphate and active vitamin D). Clinical trials and real-world studies have shown that burosumab can improve lower limb deformity, growth, pain, exercise capacity, biochemistry, rickets, and quality of life. However, the full effect of burosumab on the lives of individuals with X linked hypophosphataemia is yet to be determined. How burosumab may impact some of the lesser understood clinical features, including dental abscesses, craniosynostosis, enthesopathy, and osteoarthritis, is unclear. Whether burosumab mitigates the risk of complications associated with conventional therapy (nephrocalcinosis and hyperparathyroidism) has also not been established. There are conflicting recommendations on who should receive burosumab, when they should start it, and for how long they should continue taking it. This review summarises what is known, and more importantly what is unknown, about burosumab use in X linked hypophosphataemia. We highlight important areas for future research to better understand the impact of burosumab in XLH, improve management of XLH, assess cost benefit of, and advocate for fair and equitable access to burosumab., (© 2025 The Author(s). Journal of Paediatrics and Child Health published by John Wiley & Sons Australia, Ltd on behalf of Paediatrics and Child Health Division (The Royal Australasian College of Physicians).)

Salivary duct carcinoma (SDC) is a relatively rare, highly aggressive tumor with a poor prognosis that can be challenging to distinguish on cytology specimens. Awareness of the cytomorphologic and immunocytochemical findings is essential in arriving at a definitive diagnosis. This case report describes the primary diagnosis of a metastatic SDC on effusion fluid cytology., (© 2024 Wiley Periodicals LLC.)

A gradient in refractive index that is linear in magnitude with depth into the film is used to fit ellipsometric data for thin polymer films of poly(methyl methacrylate) (PMMA), polystyrene (PS), and poly(2-vinyl pyridine) (P2VP). We find that the linear gradient model fits provide more physically realistic refractive index values for thin films compared with the commonly used homogeneous Cauchy layer model, addressing recent reports of physically unrealistic density increases. Counter to common expectations of a simple free volume correlation between density and dynamics, we find that the direction of refractive index (density) gradient indicates a higher density near the free surface, which we rationalize based on the observed faster free surface dynamics needed to create vapor deposited stable glasses with optimized denser molecular packings. The magnitude of refractive index gradient is observed to be three times larger for PMMA than for PS films, while P2VP films exhibit a more muted response possibly reflective of a decoupling in free surface and substrate dynamics in systems with strong interfacial interactions. [ABSTRACT FROM AUTHOR]

Fibroblast growth factor 23 (FGF23) has been casually linked to numerous hypophosphatemic bone diseases, however connection with bone loss or fragility fractures is still a matter of debate. The purpose of this review is to explore and summarise the known actions of FGF23 in various pathological bone conditions. Besides implication in bone mineralisation, elevated FGF23 showed a pathological effecton bone remodelling, primarily by inhibiting osteoblast function. Unlike the weak association with bone mineral density, high values of FGF23 have been connected with fragility fracture prevalence. This review shows that its effects on bone are concomitantly present on multiple levels, affecting both qualitative and quantitative part of bone strength, eventually leading to impaired bone strength and increased tendency of fractures. Recognising FGF23 as a risk factor for the development of bone diseases and correcting its levels could lead to the reduction of morbidity and mortality in specific groups of patients. [ABSTRACT FROM AUTHOR]

The fragility of silica-based aerogels limits their potential use in various applications. These exceptional materials can be immobilized on more flexible insulation materials to form materials called 'aerogel blankets'. In situ, sol-gel deposition is one way to synthesize aerogel material directly on the fibrous matrix. This study presents aerogel blankets' formation and thermophysical performance obtained by in situ deposition of a methyltrimethoxysilane (MTMS) precursor prepared with sodium dodecyl sulphate surfactants. X-ray diffraction analysis indicates increased peak intensities, suggesting a more organized crystalline-like structure. Corresponding Raman spectroscopy and transmission electron microscopy (TEM) observations corroborate the results, highlighting the surfactant's role in promoting structural order within the aerogel. A distinct silica spherical structure was also observed in the TEM analysis. The process was carried out at ambient pressure conditions; thus, the process is scalable for large-volume production. The MTMS concentration of the sol varied in the range of 5 to 30 wt.%, resulting in different aerogel characteristics deposited onto the ceramic fiber matrix. Samples were characterized mainly for their thermal, mechanical, and morphological properties. Remarkably, the thermal conductivity performance of the obtained composite blanket showed 30% lower heat conductivity than the pristine ceramic blanket. [ABSTRACT FROM AUTHOR]

Intermixing between chemically different polymers around nanoparticles creates chemically heterogeneous layers, exhibiting unusual dynamic anomalies due to dynamic confinement and coupling phenomena in polymer nanocomposites. Interfacial mixing of chains is possible when adsorbed chains are mobile above their glass-transition temperature, leading to enhanced entanglement density at the interphase. Linear rheology data of polymer nanocomposites with chemically heterogeneous interphases around nanoparticles were analyzed over a wide frequency range to investigate the role of chain rigidity on matrix chain relaxations and particle diffusion. Our findings show that nanoparticles adsorbed with less rigid polymer move in a sub-diffusive mode. Nanoparticles adsorbed by flexible polymers can slow down the matrix polymer dynamics and particle diffusion, and this interphase effect enhances the viscoelastic properties of the whole polymer nanocomposite. [ABSTRACT FROM AUTHOR]

In polymer nanoparticle composites (PNCs) with attractive interactions between nanoparticles (NPs) and polymers, a bound layer of the polymer forms on the NP surface, with significant effects on the macroscopic properties of the PNCs. The adsorption and wetting behaviors of polymer solutions in the presence of a solid surface are critical to the fabrication process of PNCs. In this study, we use both classical density functional theory (cDFT) and molecular dynamics (MD) simulations to study dilute and semi-dilute solutions of short polymer chains near a solid surface. Using cDFT, we calculate the equilibrium properties of polymer solutions near a flat surface while varying the solvent quality, surface–fluid interactions, and the polymer chain lengths to investigate their effects on the polymer adsorption and wetting transitions. Using MD simulations, we simulate polymer solutions near solid surfaces with three different curvatures (a flat surface and NPs with two radii) to study the static conformation of the polymer bound layer near the surface and the dynamic chain adsorption process. We find that the bulk polymer concentration at which the wetting transition in the poor solvent system occurs is not affected by the difference in surface–fluid interactions; however, a threshold value of surface–fluid interaction is needed to observe the wetting transition. We also find that with good solvent, increasing the chain length or the difference in the surface–polymer interaction relative to the surface–solvent interaction increases the surface coverage of polymer segments and independent chains for all surface curvatures. Finally, we demonstrate that the polymer segmental adsorption times are heavily influenced only by the surface–fluid interactions, although polymers desorb more quickly from highly curved surfaces. [ABSTRACT FROM AUTHOR]

Endomucin (MUC14), encoded by EMCN gene, is an O-glycosylated transmembrane mucin that is mainly found in venous endothelial cells (ECs) and highly expressed in type H vessels of bone tissue. Its main biological functions include promoting endothelial generation and migration through the vascular endothelial growth factor (VEGF) signaling pathway and inhibiting the adhesion of inflammatory cells to ECs. In addition, it induces angiogenesis and promotes bone formation. Due to the excellent functions of Endomucin in the above aspects, it provides a new research target for the treatment of vascular inflammatory-related diseases and bone diseases. Based on the current understanding of its function, the research of Endomucin mainly focuses on the above two diseases. As it is known, the progression of cancer is closely related to angiogenesis. Endomucin recently is found to be differentially expressed in a variety of tumors and correlated with survival rate. The biological role of Endomucin in cancer is opaque. This article introduces the research progress of Endomucin in vascular inflammatory-related diseases and bone diseases, discusses its application value and prospect in the treatment, and collects the latest research situation of Endomucin in tumors, to provide meaningful evidence for expanding the research field of Endomucin., (© 2024 Wiley‐VCH GmbH.)

We present an integrated theoretical study of the structure, thermodynamic properties, dynamic localization, and glassy shear modulus of melt polymer nanocomposites (PNCs) that spans the three microstructural regimes of entropic depletion induced nanoparticle (NP) clustering, discrete adsorbed layer driven NP dispersion, and polymer-mediated bridging network. The evolution of equilibrium and dynamic properties with NP loading, total packing fraction, and strength of interfacial attraction is systematically studied based on a minimalist model. Structural predictions of polymer reference interaction site model integral equation theory are employed to establish the rich behavior of the interfacial cohesive force density, surface excess, and a measure of free volume as a function of PNC variables. The glassy dynamic shear modulus is predicted to be softened, reinforced, or hardly changed relative to the pure polymer melt depending on system parameters, as a result of the competing and qualitatively different influences of interfacial cohesion (physical bonding), free volume, and entropic depletion on dynamic localization and shear elasticity. The localization of polymer segments is the dominant factor in determining bulk PNC softening and reinforcement effects for moderate to strong interfacial attractions, respectively. While in the athermal entropy-dominated regime, the primary origin of mechanical reinforcement is the stress stored in the aggregated NP subsystem. The PNC shear modulus is often qualitatively correlated with the segment localization length but with notable exceptions. The present work provides the foundation for developing a theory of segmental relaxation, Tg changes, and collective NP dynamics in PNCs based on a self-consistent treatment of the cooperative activated motions of segments and NPs. [ABSTRACT FROM AUTHOR]

Density changes in thin polymer films have long been considered as a possible explanation for shifts in the thickness-dependent glass transition temperature Tg(h) in such nanoconfined systems, given that the glass transition is fundamentally associated with packing frustration during material densification on cooling. We use ellipsometry to compare the temperature-dependent refractive index with decreasing thickness n(h) for supported films of poly(2-vinyl pyridine) (P2VP), poly(methyl methacrylate) (PMMA), and polystyrene (PS), as these polymers have different silica substrate interactions. We observe similar n(h) trends for all three polymers, with near equivalence of P2VP and PS, characterized by a large apparent increase in refractive index for h ≤ 40 nm–65 nm depending on the polymer. Possible sources of molecular dipole orientation within the film are tested by varying molecular weight, polydispersity, chain conformation, and substrate chemistry. Such film inhomogeneities associated with non-uniform polarizability would invalidate the use of homogeneous layer approximations inherent in most thin film analysis methods, which we believe likely explains recent reports of large unphysical increases in film density with decreasing thickness by a variety of different experimental techniques. [ABSTRACT FROM AUTHOR]

This article discusses the 2023 Annual Meeting of the American Society for Bone and Mineral Research (ASBMR). The article presents a list of award recipients as well as all abstracts of all research presented at the meeting. Research topics include bone mineral density, osteoporosis and osteoclasts. [Extracted from the article]

To solve the conventional problems of chemically cross‐linked polymers, the vitrimer concept has attracted great attention because the associative bond‐exchange nature in vitrimers provides sustainable functions. So far, various vitrimer designs have been reported using different polymer species with compatible bond exchange mechanisms. However, the biggest barrier for the practical application may be the elaborated functional group modification of the starting components and the limited availability of suitable monomers. As a much simpler preparation, recently, a one‐shot preparation of vitrimers from commodity polyesters with no special reactive functional groups by blending and heating with tetra‐functional epoxy molecules and base catalysts has been proposed. In this study, further one‐shot preparation of composite vitrimers with silica nanoparticles (SNPs) is developed. The effects of SNPs on the cross‐linking process and thermo/mechanical properties are first assessed, which reveals the formation of a bound rubber phase on the surfaces of the SNPs. The bound rubber phase also affects the bond exchange features of vitrimers, especially the distribution of relaxation time. Overall, the present facile preparation of composite vitrimers with enhanced mechanical properties could be a hint for practical application, whereas the knowledge on the unique relaxation behaviors of composite vitrimers should be beneficial in the fundamental sense. [ABSTRACT FROM AUTHOR]

The emerging applications of thermally conductive elastomer composites in modern electronic devices for heat dissipation require them to maintain both high toughness and resilience under thermomechanical stresses. However, such a combination of thermal conductivity and desired mechanical characteristics is extremely challenging to achieve in elastomer composites. Here this long-standing mismatch is resolved via regulating interfacial structure and dynamics response. This regulation is realized both by tuning the molecular weight of the dangling chains in the polymer networks and by silane grafting of the fillers, thereby creating a broad dynamic-gradient interfacial region comprising of entanglements. These entanglements can provide the slipping topological constraint that allows for tension equalization between and along the chains, while also tightening into rigid knots to prevent chain disentanglement upon stretching. Combined with ultrahigh loading of aluminum-fillers (90 wt%), this design provides a low Young's modulus (350.0 kPa), high fracture toughness (831.5 J m -2 ), excellent resilience (79%) and enhanced thermal conductivity (3.20 W m -1 k -1 ). This work presents a generalizable preparation strategy toward engineering soft, tough, and resilient high-filled elastomer composites, suitable for complex environments, such as automotive electronics, and wearable devices., (© 2024 Wiley‐VCH GmbH.)

We perform coarse-grained simulations of model unentangled polymer materials to quantify the range over which interfaces alter the structure and dynamics in the vicinity of the interface. We study the interfacial zone around nanoparticles (NPs) in model polymer-NP composites with variable NP diameter, as well as the interfacial zone at the solid substrate and free surface of thin supported polymer films. These interfaces alter both the segmental packing and mobility in an interfacial zone. Variable NP size allows us to gain insight into the effect of boundary curvature, where the film is the limit of zero curvature. We find that the scale for perturbations of the density is relatively small and decreases on cooling for all cases. In other words, the interfaces become more sharply defined on cooling, as naively expected. In contrast, the interfacial mobility scale ξ for both NPs and supported films increases on cooling and is on the order of a few nanometers, regardless of the polymer-interfacial interaction strength. Additionally, the dynamical interfacial scale of the film substrate is consistent with a limiting value for polymer-NP composites as the NP size grows. These findings are based on a simple quantitative model to describe the distance dependence of relaxation that should be applicable to many interfacial polymer materials. [ABSTRACT FROM AUTHOR]

We present a systematic investigation on the effect of adding nanoparticles on the dynamics of polymer chains by using coarse-grained molecular dynamics simulation. The dynamics is characterized by three aspects: molecular motion, relaxation at different length scales, and dynamical heterogeneity. It is found that the motion of polymer chains slows down and the deviation from Gaussian distribution becomes more pronounced with increasing nanoparticle volume fractions. For polymer nanocomposites with R ≤ Rg, the relaxation at the wave vector q = 7.0 displays multistep decay, consistent with the previous reports in strongly interacting polymer nanocomposites. Moreover, a qualitatively universal law is established that dynamic heterogeneity at whole chain's scale follows a nonmonotonic increase with increasing nanoparticle loadings, where the volume fraction of the maximum dynamic heterogeneity corresponds to the particle loading when the average distance between nanoparticles is equal to the Kuhn length of polymer chains. We show that the decoupling between whole chain's dynamics and segment dynamics is responsible for the nonmonotonic behavior of dynamic heterogeneity of whole chains. [ABSTRACT FROM AUTHOR]

It is widely appreciated that an attractive polymer-substrate interaction can slow relaxation in thin supported polymer films and polymer nanocomposites. Recent measurements and simulations on nancomposites have indicated that this slowing of polymer dynamics occurs more strongly near a highly attractive particle surface where a "bound" layer having a much lower mobility can form, strongly influencing the thermodynamics and dynamics of the film. Here we use molecular simulations to show that a bound interfacial layer having a very similar nature arises in thin supported polymer films when the polymer-polymer attraction is stronger than the polymer-polymer interaction strength. This bound polymer layer effectively insulates the remainder of the film from the strong interfacial interactions, and the resulting thermodynamically determined Tg is relatively insensitive to the polymer-substrate interaction strength when it exceeds that of the polymer-polymer interactions. The presence of this layer gives rise to an additional relaxation process in the self-intermediate scattering function that is not observed in the bulk material and leads to a slowing down of the average relaxation time of the film as a whole. On the other hand, the average relaxation time of the film outside the bound layer does not grow in proportion to the strength of the substrate attraction due to the weak coupling of the substrate relaxation to the relaxation in the interior of the film. At large substrate attraction, the bound layer effectively "cloaks" the substrate, reducing the effect of the polymer-surface interaction on Tg. [ABSTRACT FROM AUTHOR]

The absolute heat capacity of a matrix‐free polystyrene grafted silica nanocomposite system is investigated using ultrafast Flash differential scanning calorimetry (Flash DSC) and compared to results for a neat polystyrene sample of similar molecular weight. The heat capacity of the polymer in the nanocomposite is 8% lower than that of the neat polystyrene. In addition, the step change in heat capacity at the glass transition Tg is 15% lower, indicating a 2 nm‐thick immobile layer of polymer around the nanoparticles. There is neither an increase in the nanocomposite heat capacity towards that of the neat material nor any additional ∆Cp steps, indicating that the glassy layer around the nanoparticles remains immobile up to 300°C. In addition to the analysis of the absolute heat capacity, the dynamic temperature gradient in the Flash DSC sample increases linearly with increasing rate of measurement, whereas the noise in the heat capacity data increases linearly with the reciprocal of the scanning rate; the optimum rate for measurements lies between 300 and 1000 K/s for the samples studied here and will depend on the sample thickness. [ABSTRACT FROM AUTHOR]

Arbutus unedo L. (strawberry tree, Ericaceae) is a woody species with a circum-Mediterranean distribution. It has considerable ecological relevance in southern European forests due to its resilience to abiotic and biotic stressors. Its edible red berries are used in the production of traditional products, including an expensive spirit. Several compounds extracted from the species have bioactive properties used by the cosmetic and pharmaceutical industries. The strawberry tree has gone from a neglected species to become a highly valuable crop with large cultivated areas in southern European and North African countries. Due to an increasing demand from farmers for plants with improved features, researchers have been trying to improve this species through conventional and biotechnological tools, focusing mainly on population analysis using molecular markers, in vitro cloning, tolerance to biotic and abiotic stresses, and intraspecific crosses to obtain genotypes with new characteristics. The objective of this review is to gather and update information about the species and make it available to researchers and stakeholders. Future research areas that are considered a priority for this species are highlighted. [ABSTRACT FROM AUTHOR]

We present how altering the chain flexibility affects the nanoscale organization of polymer-grafted nanoparticles (PGNPs) and its ultimate impact on macroscale thermal properties. To isolate the role of chain flexibility on wetting behavior in athermal polymer nanocomposites (PNC), the graft and matrix chemistry is kept identical by utilizing 1,3-cyclohexadiene-based polymer materials. Increasing the rigidity and molecular weight of both the graft and matrix is found to favor mixing of poly(1,3-cyclohexadiene) PCHD-grafted silica NPs with the matrix, supported by a concomitant increase in glass transition temperatures of the PNCs. Further, the associated entropic factors that drive wetting behavior and dispersion of PGNPs are discussed, emphasizing the dominant role-played by chain flexibility. Alterations in graft flexibility had the strongest impact on dispersion and Tg values of the PNC, while molecular weight (MW) plays a secondary role. This investigation is a unique demonstration of how chain flexibility alteration in athermal semiflexible systems can be used to alter NP organization by altering filler-matrix wettability which also impacts thermal properties. [ABSTRACT FROM AUTHOR]

The detailed nature of spatially heterogeneous dynamics of glycerol-silica nanocomposites is unraveled by combining dielectric spectroscopy with atomistic simulation and statistical mechanical theory. Analysis of the spatial mobility gradient shows no "glassy" layer, but the ɑ-relaxation time near the nanoparticle grows with cooling faster than the ɑ-relaxation time in the bulk and is ~20 times longer at low temperatures. The interfacial layer thickness increases from ~1.8 nm at higher temperatures to ~3.5 nm upon cooling to near bulk Tg. A real space microscopic description of the mobility gradient is constructed by synergistically combining high temperature atomistic simulation with theory. Our analysis suggests that the interfacial slowing down arises mainly due to an increase of the local cage scale barrier for activated hopping induced by enhanced packing and densification near the nanoparticle surface. The theory is employed to predict how local surface densification can be manipulated to control layer dynamics and shear rigidity over a wide temperature range. [ABSTRACT FROM AUTHOR]

In a nano‐assembly of soft polymer chains and hard filler nanoparticles (NPs), the intermolecular interactions at the polymer‐filler interface lead to variations in viscoelastic properties in the vicinity of the NP surface. However, unravelling the molecular parameters controlling the entropic and enthalpic interactions, including polymer chain conformation, dynamics, dispersion mechanisms and confinement effects across the interfacial region, has been remote and challenging. Even though the polymer's molecular structure and the NPs surface chemistry contribute to these interfacial interactions, the underlying mechanism behind the enhanced dynamic‐mechanical performance is still a hot topic of debate. By controlling the chemistry of NPs and polymer matrix in model nanocomposites, many efforts have been made in elucidating the physical origin of the structure and dynamics of the interfacial polymer layer with estimates varying from 1 to 10 nm around the spherical NPs. Therefore, understanding the interface structure and dynamics influenced by polymer‐NP interaction is of great technological importance. In this article, the latest polymer‐particle interface literature developments are reviewed where computational simulations, calorimetry, and dielectric spectroscopy studies have been used to examine the constraints levied by the interface structure on segmental relaxation dynamics of polymer chains in the vicinity of NP surface. [ABSTRACT FROM AUTHOR]

Poly(butylene terephthalate) (PBT) nanocomposites reinforced with different weight fractions of montmorillonite (MMT), and nanoprecipitated calcium carbonate (NPCC) were prepared by a two‐step melt compounding method. X‐ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses were employed to explore the effect of nanofiller inclusion on the crystalline structure of PBT nanocomposites. The mobile amorphous fraction (MAF) and the rigid amorphous fraction (RAF) were first measured using the specific heat capacity (Cp) and melting enthalpy data. However, the contributors to total RAF, including interfacial RAF (RAFint) and crystalline RAF (RAFc), could not be discerned using only DSC. A novel and simple method was hence developed by employing a combined DSC‐dynamic mechanical thermal analysis (DMTA) approach (CDDA) to disentangle the RAF components and determine the fractions of constrained volume constituents. To validate the results, the MAF calculated by CDDA were compared to those of DSC. The values obtained using CDDA were relatively higher, owing to the more significant sensitivity of this approach to polymer chain mobility. [ABSTRACT FROM AUTHOR]

We study the interfacial structure and dynamics of a polymer nanocomposite (PNC) composed of octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) and poly(2-vinylpyridine) (P2VP) by performing full atomistic molecular dynamics simulations. There are eight aminophenyl groups grafted on the surface of the OAPS particle and the particle has a size comparable to the Kuhn segment of P2VP. These aminophenyl groups can form hydrogen bonds (HBs) with pyridine rings from surrounding P2VP chains. We found that OAPS can form ∼2 HBs on average with surrounding polymer chains. The effect of the HBs is investigated in detail by either switching on or off these HBs in our simulation. By analyzing the interfacial static packing structure and dynamic properties, we demonstrate that the system has an ∼1 nm interface width, similar to the OAPS particle size. We also found that HBs can prevent the further penetration of polymers into the inner zone (grafting layer) of the OAPS, and therefore keep the P2VP chains in the outer layer (>1 nm), remaining bulk-like, which is well consistent with experimental results. In addition, we found that NP diffusion is coupled to the absorbed polymer chains, which also dramatically slows down the diffusion of polymer segments in return. The core–shell model in which the NP and absorbed polymers diffuse as a single object is validated here at the full atomistic level. These results provide atomistic insights into the unique structure and dynamics in the small attractive NP–polymer interfacial region. We hope these results will be helpful for the understanding of peculiar phenomena in attractive polymer nanocomposites containing small NPs. [ABSTRACT FROM AUTHOR]

Colloidal silica nanoparticles (NPs) modified with eight different silane coupling agents were incorporated into an amorphous poly(tetramethylene oxide)‐based polyurethane–urea copolymer matrix at a concentration of 10 wt % (4.4 vol %) in order to investigate the effect of their surface chemistry on the structure–property behavior of the resulting nanocomposites. The rigid amorphous fraction (RAF) of the nanocomposite matrix as determined by differential scanning calorimetry and dynamic mechanical analysis was confirmed to vary significantly with the surface chemistry of the NPs and to be strongly correlated with the bulk mechanical properties in simple tension. Hence, nanocomposites with an RAF of about 30 wt % showed a 120% increase in Young's modulus, a 25% increase in tensile strength, a 15% decrease in elongation at break with respect to the neat matrix, which had no detectable RAF, whereas nanocomposites with an RAF of less than 5% showed a 60% increase in Young's modulus, a 10% increase in tensile strength and a 5% decrease in the elongation at break. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2543–2556 [ABSTRACT FROM AUTHOR]

2019 Annual Meeting of the American Society for Bone and Mineral Research Orange County Convention Center, Orlando, Florida, USA September 20-23, 2019. [Extracted from the article]

In order to enhance dielectric properties and energy storage density of poly(vinylidene fluoride‐hexafluoro propylene) (PVDF‐HFP), surface charged gas‐phase Al2O3 nanoparticles (GP‐Al2O3, with positive surface charges, ε' ≈ 10) are selected as fillers to fabricate PVDF‐HFP‐based composites via simple physical blending and hot‐molding techniques. The results show that GP‐Al2O3 are dispersed homogeneously in the PVDF‐HFP matrix and the existence of nanoscale interface layer (matrix‐filler) is investigated by SAXS. The dielectric constant of the composites filled with 10 wt % GP‐Al2O3 is 100.5 at 1 Hz, which is 5.6 times higher than that of pure PVDF‐HFP. The maximum energy storage density of the composite is 4.06 J cm−3 at an electrical field of 900 kV mm−1 with GP‐Al2O3 content of 1 wt %. Experimental results show that GP‐Al2O3 could induce uniform fillers' distribution and increase the concentration of electroactive β‐phase as well as enhance interfacial polarization in the matrix, which resulted in enhancements of dielectric constant and energy storage density of the PVDF‐HFP composites. This work demonstrates that surface charged inorganic‐oxide nanoparticles exhibit promising potential in fabricating ferroelectric polymer composites with relatively high dielectric constant and energy storage. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 574–583 [ABSTRACT FROM AUTHOR]

This paper presents a nonlinear viscoelastic model for polymer nanocomposites and the computed model response to large amplitude oscillatory shear flow. The model predicts the stress in a mixture of entangled polymer chains, with different convective constraint release (CCR) rates for free chains and nanoparticle‐attached chains, through an averaging scheme which is consistent with double reptation in the Marrucci–Ianniruberto constitutive equation. The nonlinear response of the mixture is evaluated both numerically in terms of Q and by an asymptotic analysis in terms of four frequency dependent parameters of medium amplitude oscillatory shear (MAOS) as well as the intrinsic nonlinearity parameter Q0. In the case of free polymer chains alone, the MAOS signatures are comparable to those of the Giesekus model with the notable difference of a minimum in the elastic parameter [e1] at De >1. The viscous nonlinear parameters of the mixture model depart significantly from those of the free chains, especially in mixtures where the CCR parameter for attached chains is larger than that for the free chains: [v1] has a prominent minimum and [v3] has a prominent maximum near De = 2/c, the low frequency plateau region, along with a higher Q0 compared to the matrix at all Deborah numbers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 62–76 The nonlinear viscoelastic response to large amplitude oscillatory shear of mixtures of entangled polymer chains—both unattached and attached to nanoparticle surfaces—has been modeled using a double reptation formulation of the Marrucci–Ianniruberto tube model. The mixture model developed here also incorporates different convective constraint release (CCR) parameters (βa > βf) for the two types of chains in nanoparticle filled polymer melts. The results show that entanglements between the particle attached chains lead to the greatest extent of nonlinearity. [ABSTRACT FROM AUTHOR]

Abstract: Characterization of polymers at the nanometer‐length scale has become increasingly important with the growth and expansion of nanotechnology. Due to limitations of sensitivity and specificity that persist with traditional materials characterization techniques, there is a growing need to develop new tools to measure the properties of confined polymer systems. Within the past 20 years, fluorescence characterization techniques have emerged to address this challenge. This review focuses on the employment of fluorescence techniques such as temperature‐ and time‐dependent steady‐state intensity, fluorescence recovery after photobleaching, and nonradiative energy transfer to study polymer behavior at the nanoscale. Properties discussed include glass transition temperature, physical aging, diffusion and mobility, and mechanical response. Particular attention is given to the unique insight gained through these techniques as well as opportunities for future studies. The ability of fluorescence to obtain location‐ and component‐specific measurements with nanometer resolution for a variety of polymer chemistries and geometries on a bench‐top instrument provides a valuable contribution to the characterization and understanding of polymers at the nanoscale. [ABSTRACT FROM AUTHOR]

ABSTRACT With particular focus on the characterization of polymer-nanoparticle interaction, the effects of polymer molecular weight ( Mn) on confined crystallization of the interfacial region in poly(ethylene oxide) (PEO)/silica (SiO2) composites were investigated, employing differential scanning calorimetry, dynamic light scattering, and proton nuclear magnetic resonance relaxation techniques. Dependence of crystallization on Mn in PEO/SiO2 composites is found to be closely related to the microstructure changes in adsorbed polymer. PEO adsorbs in a manner that produces a tightly bound layer (amorphous) with constant thickness, independent of Mn, and creates a loosely bound layer with flattened structure for short PEO chains but coiled conformation for long chains. The contribution of this Mn-dependent layer to crystallization grows with Mn, showing a transition from non-crystalline phase to the formation of a crystallization peak (−25 to −33 °C), and then to crystallization together with non-adsorbed PEO. The comprehensive description of the interfacial region should be a helpful tool in the preparation and modification of polymer nanocomposites. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1608-1616 [ABSTRACT FROM AUTHOR]

Nanocomposites based on poly( l-lactide) (PLA) and organically modified Ni/Al layered double hydroxides (NiAl/LDHs) are prepared by melt blending and investigated by a combination of size exclusion chromatography, differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), wide-angle X-ray scattering, and broadband dielectric spectroscopy. A detailed comparison to the behavior of the corresponding MgAl/LDH-PLA nanocomposites is made. SAXS investigations show that the morphology of the NiAl/LDH-PLA nanocomposites is more intercalated compared to the MgAl/LDH based PLA nanocomposite, which is more exfoliated. The DSC investigation gives a different dependence of the degree of crystallization on the concentration of LDH for NiAl/LDH-PLA than for MgAl/LDH-PLA nanocomposite system. These differences are discussed taking the differences of the morphologies of both systems into account. Broadband dielectric spectroscopy reveals information about the molecular dynamics where essential differences are observed for all relaxation processes taking place in both systems which were related to the different morphologies. [ABSTRACT FROM AUTHOR]