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Because most real-world domains intended to be supported by an information system are complex, practitioners often use multiple different types of conceptual modeling scripts to understand them. We performed two experiments to examine how two theoretical factors of multiple scripts— combined ontological completeness and ontological overlap—influence how users develop an understanding of a real-world domain from multiple scripts. Results of the first experiment show that to some degree, ontological overlap improves participants’ understanding of a domain, more so than combined ontological completeness. In the second experiment, we tracked the eye movement data of participants to understand how ontological overlap between scripts impacts users’ information search and cognitive integration processes. We found that some occurrence of semantically similar constructs between scripts helps individuals to identify and relate constructs presented in different scripts. Users, therefore, can identify and focus on script areas that are relevant to their problem tasks. However, a high level of ontological overlap decreases the attention paid by participants to relevant task-specific areas because they spend more time searching for relevant information. Together, our findings both refine and extend existing conceptual modeling theory. We clarify the dialectics between the full and parsimonious real-world representations offered through multiple scripts and the individual’s understanding of the domain that is represented by those scripts.

We investigated the segmental dynamics of asymmetrically confined polymer films and report an unusual phenomenon in which the presence and thickness of a soft confining layer are responsible for significant changes in the segmental dynamics of the confined films. Specifically, the segmental dynamics of poly(vinyl alcohol) (PVA) thin films asymmetrically confined between hard aluminum (Al), and soft polystyrene (PS) films are shown to shift by as much as half an order of magnitude upon changes in the thicknesses of the confining PS layer. These effects are more significant than those due to symmetric confinement between hard Al substrates or exposure to a free surface. These observations, partially rationalized in terms of recent simulations and theory, implicate the role of the moduli of the confining layers.

We show evidence of thickness-dependent elastic mechanical moduli that are associated largely with the effects of architecture (topology) and the overall shape of the macromolecule. Atomic force microscopy (AFM) based nanoindentation experiments were performed on linear chain polystyrene (LPS) and star-shaped polystyrene (SPS) macromolecules of varying functionalities (number of arms, f) and molecular weights per arm Mwarm. The out-of-plane elastic moduli E(h) increased with decreasing film thickness, h, for h less than a threshold film thickness, hth. For SPS with f ≤ 64 and Mwarm > 9 kg/mol, the dependencies of E(h) on h were virtually identical for the linear chains. Notably, however, for SPS with f = 64 and Mwarm = 9 kg/mol (SPS-9k-64), the hth was over 50% larger than that of the other polymers. These observations are rationalized in terms of the structure of the polymer for high f and sufficiently small Mwarm and not in terms of the influence of interfacial interactions.

In thin film A/B polymer/polymer mixtures, the formation of a layer at the free surface, with average composition that differs from the bulk, due to the preferential segregation of the lower cohesive energy density component, is well understood. While much is also understood about this surface layer formation and growth to date, virtually nothing is known about the surface dynamics of the chains in such mixtures. Questions about the surface chain dynamics in relation to the bulk have remained unanswered. With the use of X-ray photon correlation spectroscopy (XPCS) we show that the dynamics of poly(vinyl methyl ether) (PVME) chains at the free surface of polystyrene (PS)/PVME thin film mixtures can be orders of magnitude larger than the PVME chains in the bulk. These dynamics manifest from differences between the local compositions of the blend at the free surface and the bulk, as well as film thickness constraints.

The performance of conjugated polymer (CP)-based electronic devices relies on optimal charge carrier mobilities, which are determined by monomeric architecture, degree of polymerization, chain conformation, and the nano- and mesoscale morphologies. With regard to the latter, we discuss two effects that have received limited attention in the literature, yet important for device performance optimization: (1) the role of morphological disorder and of CP/substrate interactions on the in-plane and out-of-plane carrier transport in CPs; (2) the impact of morphological disorder on charge transfer at the CP/substrate interface. The emergence of film thickness-dependent carrier mobilities, varying over two orders of magnitude within a length scale of 200 nm, and band-bending phenomena, extending tens of nanometers within the CP, are associated with these effects. These findings suggest areas for further research in order to enable widespread applications of next-generation CP-based devices. Graphical abstract

Upon quenching a polymer melt to a temperature T below its glass transition temperature Tg, structural relaxations, physical aging, enable the material to return to equilibrium. Whereas the physica...

The transport of charge carriers throughout an active conjugated polymer (CP) host, characterized by a heterogeneous morphology of locally varying degrees of order and disorder, profoundly influences the performance of CP-based electronic devices, including diodes, photovoltaics, sensors, and supercapacitors. Out-of-plane charge carrier mobilities (μout-of-plane) across the bulk of the active material host and in-plane mobilities (μin-plane) parallel to a substrate are highly sensitive to local morphological features along their migration pathways. In general, the magnitudes of μout-of-plane and μin-plane are very different, in part because these carriers experience different morphological environments along their migration pathways. Suppressing the impact of variations in the morphological order/disorder on carrier migration remains an important challenge. While much is known about μin-plane and its optimization for devices, the current challenges are associated with μout-of-plane and its optimization for device performance. Therefore, this review is devoted to strategies for improving μout-of-plane in neat CP films and the implications for more complex systems, such as D:A blends which are relevant to OPV devices. The specific strategies discussed for improving μout-of-plane include solvent/field processing methods, chemical modification, thickness confinement, chemical additives, and different post-annealing strategies, including annealing with supercritical fluids. This review leverages the most recent fundamental understanding of mechanisms of charge transport and connections to morphology, identifying robust design strategies for targeted improvements of μout-of-plane.

Obesity-related type 2 diabetes (DM) is a major public health concern. Adipose tissue metabolic dysfunction, including fibrosis, plays a central role in DM pathogenesis. Obesity is associated with changes in adipose tissue extracellular matrix (ECM), but the impact of these changes on adipose tissue mechanics and their role in metabolic disease is poorly defined. This study utilized atomic force microscopy (AFM) to quantify difference in elasticity between human DM and non-diabetic (NDM) visceral adipose tissue. The mean elastic modulus of DM adipose tissue was twice that of NDM adipose tissue (11.50 kPa vs. 4.48 kPa) to a 95% confidence level, with significant variability in elasticity of DM compared to NDM adipose tissue. Histologic and chemical measures of fibrosis revealed increased hydroxyproline content in DM adipose tissue, but no difference in Sirius Red staining between DM and NDM tissues. These findings support the hypothesis that fibrosis, evidenced by increased elastic modulus, is enhanced in DM adipose tissue, and suggest that measures of tissue mechanics may better resolve disease-specific differences in adipose tissue fibrosis compared with histologic measures. These data demonstrate the power of AFM nanoindentation to probe tissue mechanics, and delineate the impact of metabolic disease on the mechanical properties of adipose tissue.

In situ, real-time polarized Raman spectroscopy was used to measure electrostatically induced carbon nanotube alignment in a polymer matrix. Discrete and reversible asymptotes of carbon nanotube G-band intensity were observed as a function of the applied electric field strength. It is proposed that as the electric field is increased, certain populations of carbon nanotubes attain sufficient alignment energy to overcome the randomizing thermal energy of the system. This is attributed to the electrostatic torque being a function of nanotube length, a relation that has been shown for dielectric rods and is extended here to carbon nanotubes. Nanotube batches of varying length distributions (hundreds of nanometers to micron-length) were created with different amounts of sonication energy. These distributions were quantified with atomic force microscopy measurements, and a model was developed relating these length distributions to the change in nanotube alignment at various electric field strengths. Nanotube polarizabilities determined from the model ( α = 10 − 30 − 10 − 32 F ⋅ m 2 ) were consistent with previously reported values. The effects of processing parameters such as sonication on the degree of achievable alignment as well as its implications are also discussed.

Spatial compositional heterogeneity strongly influences the dynamics of the A and B components of bulk miscible blends. Its effects are especially apparent in mixtures, such as poly(vinyl methyl ether) (PVME)/polystyrene (PS), where there exist significant disparities between the component glass transition temperatures (Tgs) and relaxation times. The relaxation processes characterized by distinct temperature dependencies and relaxation rates manifest different local compositional environments for temperatures above and below the glass transition temperature of the miscible blend. This same behavior is shown to exist in miscible PS/PVME films as thin as 100 nm. Moreover, in thin films, the characteristic segmental relaxation times τ of the PVME component of miscible PVME/PS blends confined between aluminum (Al) substrates decrease with increasing molecular weight M of the PS component. These relaxation rates are film thickness dependent, in films up to a few hundred nanometers in thickness. This is in rema...

Viscoelastic properties are central for gels and other materials. Simultaneously, high storage and loss moduli are difficult to attain due to their contrarian requirements to chemical structure. Biomimetic inorganic nanoparticles offer a promising toolbox for multiscale engineering of gel mechanics, but a conceptual framework for their molecular, nanoscale, mesoscale, and microscale engineering as viscoelastic materials is absent. Here we show nanoparticle gels with simultaneously high storage and loss moduli from CdTe nanoparticles. Viscoelastic figure of merit reaches 1.83 MPa exceeding that of comparable gels by 100–1000 times for glutathione-stabilized nanoparticles. The gels made from the smallest nanoparticles display the highest stiffness, which was attributed to the drastic change of GSH configurations when nanoparticles decrease in size. A computational model accounting for the difference in nanoparticle interactions for variable GSH configurations describes the unusual trends of nanoparticle gel viscoelasticity. These observations are generalizable to other NP gels interconnected by supramolecular interactions and lead to materials with high-load bearing abilities and energy dissipation needed for multiple technologies., Achieving simultaneous high storage and loss moduli in gels is difficult due to the opposite chemical structure requirements needed for such properties. Here the authors show a spectrum of gels containing CdTe nanoparticles stabilized by glutathione that have such properties which can be rationalised through the developed model.