Summary: The effect of polydispersity on polymer blend phase behavior is studied by in situ small‐angle X‐ray scattering. In a polydisperse polyethylene (PE)/isotactic poly(propylene) (iPP) blend, the enthalpic portion of the interaction parameter is greater than that of a corresponding blend with lower polydispersity. This is attributed to the presence of long chains, which provide a higher interaction energy and packing constraint, reducing the system miscibility. As expected, the radius of gyration is higher in the system with higher polydispersity.
Comparison of phase diagrams of the iPP/PE system used in this study (thin lines) with that obtained from the literature (thick lines). The solid lines represent binodals and the dashed lines are spinodals. 相似文献
We consider nanosized artificial or biological machines working in steady state enforced by imposing nonequilibrium concentrations of solutes or by applying external forces, torques, or electric fields. For unicyclic and strongly coupled multicyclic machines, efficiency at maximum power is not bounded by the linear response value 1/2. For strong driving, it can even approach the thermodynamic limit 1. Quite generally, such machines fall into three different classes characterized, respectively, as "strong and efficient," "strong and inefficient," and "balanced." For weakly coupled multicyclic machines, efficiency at maximum power has lost any universality even in the linear response regime. 相似文献
Steady-state and dynamic flying of a self-acting magnetic disk slider over a hard disk are considered. Some tasks for computations are formulated and the possibilities of developed numerical codes are illustrated. Numerical results of dynamic flying over a disk surface with an obstacle are in agreement with experimental data. 相似文献
The present study describes an approach for the
scale-bridging modeling of ferroic materials as functional elements
in micro- and nanoelectronic devices. Ferroic materials are
characterized by temperature-dependent complex ordering phenomena of
the internal magnetic, electronic, and structural degrees of freedom
with several involved length and time scales. Hence, the modelling
of such compounds is not straightforward, but relies on a
combination of electronic-structure-based methods like ab-initio and
density-functional schemes with classical particle-based approaches
given by Monte-Carlo simulations with Ising, lattice-gas, or
Heisenberg Hamiltonians, which incorporate material-specific
parameters both from theory and experiment. The interplay of those
methods is demonstrated for device concepts based on electroceramic
materials like ferroelectrics and multiferroics, whose functionality
is closely related with their propensity towards structural and
magnetic polymorphism.
In the present case, such scale-bridging techniques are employed to aid the
development of an organic field effect transistor on a ferroelectric
substrate generated by the self-assembly of field-sensitive molecules
on the surfaces of ferroic oxides. Electronic-structure-based methods
yield the microscopic properties of the oxide, the surface, the molecules, and the
respective interactions. They are combined with classical particle-based methods on a
scale-hopping basis. This combination allows to study the morphology evolution
during the self-assembly of larger adsorbate arrays on the (defective) oxide
surface and to investigate the interplay of low-temperature magnetic ordering
phenomena with the ferroelectric functionality at higher temperatures in
multiferroic oxides like the hexagonal manganites. The combination of
density-functional data with classical continuum modelling also yielded
a model Hamiltonian for the quick determination of the properties of a
gate structure based on bio-functionalized carbon nanotubes. 相似文献
