Materials Literature
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The segmental dynamics of miscible polymer blends have been the focus of much recent research since the two constituents typically appear to experience different average dynamic environments. It has been suggested that these results can be attributed to concentration fluctuations coupled to chain connectivity effects.…
Abstract The X‐ray structure of the sodium salt of [Gd(DOTP)] 5− shows two different chelates, [Gd (1) (DOTP)] 5− and [Gd (2) (DOTP)] 5− , bound at either surface of a sheet formed by a cluster of hydrated Na + ions. Each [Gd (1) (DOTP)] 5− anion binds directly to four Na + ions of this cluster through the free oxygen…
This study demonstrates that bridging (and possibly knotted looping) pentablock configurations in CEC/CECEC (triblock/pentablock) blends play significant roles in the shear-induced alignment and tensile mechanical properties of lamellae-forming block copolymers. Adding just 15 wt % pentablock to the triblock copolymer…
We report on the competitive role of hydrogen bonding and electrostatic interactions in growth and stability of polyelectrolyte multilayers (PEMs) in a wide range of pH. The system was a cationic copolymer of acrylamide and dimethyldiallylammonium chloride (PAAm-DMDAAC) containing 50% cationic units and poly(methacryl…
New results of dielectric spectroscopy in semicrystalline nylon-6 samples with different moisture contents are presented by using a wide frequency (10 -2 −3 × 10 6 Hz) and temperature range (133−433 K). The dielectric absorption spectra in frequency domain are decomposed in Cole−Cole distributions corresponding to the…
The study computes evolutionary tracks for 13-16 mass values (depending on the assumed chemical composition) in the range 0.15-1.25 solar mass for each of 10 metallicities between -2.26 and -0.47 (Fe/H). A total of 46 tracks are evolved to the helium flash point. The properties of selected models along the entire evol…
Using light scattering spectroscopy, we demonstrate that a transition from small molecular behavior to Rouse dynamics in poly(dimethylsiloxane) (PDMS) is a smooth function of molecular weight, M w . The asymptotic Rouse behavior is achieved when the chain begins to display Gaussian behavior. Surprisingly, the molecula…
Individual PbSe nanocrystals (NCs) were prepared by a chemical reaction between lead-cyclohexanebutirate and tri-butyl-phosphine/selenium precursors in a tri-octyl-phosphine oxide/tri-butyl-phosphine surfactant, at 118 °C. Increasing precursor concentration, accompanied by an additional heating, up to 150 °C, enabled…
Poly(lactic acid) (PLA) were grafted to both ends of Pluronic F127 (PEO−PPO−PEO) to produce novel amphiphilic PLA-F127−PLA block copolymers. The aggregation behaviors of three different modified polymers were examined by laser light scattering and transmission electron microscopic techniques. The structure of aggregat…
We observed novel nanoscale surface structures of segregated pinned micelles and craterlike micelles formed by grafted Y-shaped molecules and their reversible reorganization in selective solvents. The Y-shaped molecules have two incompatible polymer chains (polystyrene and poly(tert-butyl acrylate)) attached to a func…
Hyperbranched polymers have received significant attention due to their unique combination of low viscosity, excellent solubility, and facile synthesis. This paper describes an efficient approach to hyperbranched poly(aryl ester)s via the polycondensation of A 2 and B 3 monomers. A dilute bisphenol A (A 2 ) solution w…
The ground- and excited-state properties of a series of meso -tetraphenylporphyrin (H 2 TPP) diacids, [H 4 TPP](X) 2 (X = F, Cl, Br, I), ad hoc synthesized and characterized by 1 H NMR, RLS, and UV−vis spectroscopies, have been studied theoretically using density functional theory (DFT) and time-dependent density func…
Geometric disassembly of dendritic structures was realized by a cascade cleavage reaction triggered by an initially stimulated group at the dendrimer core. Release of an exponential number of dendrimer fragments was a result of the branching nature of the cleavage pathway. Evidence for the completion of the disassembl…
Ordered arrays of Au, Ni, and Si nanorings have been fabricated using Ar + sputter redeposition of material in a porous alumina mask. Typical ring dimensions are 50 nm inner diameter and 10−15 nm wall thickness with heights ranging from 50 to 200 nm. Ring composition was confirmed by electron microscopy. Ring diameter…
A novel synthetic approach to a series of bulky triarylamines substituted by various electron-withdrawing groups and forming amorphous materials is presented. Under vacuum evaporation, thin films with high optical quality are obtained and exhibit spontaneous second-order nonlinear optical activity. This unprecedented…
In this work we explore the transmission properties of a single slit in a metallic screen. We analyze the dependence of these properties on both slit width and angle of incident radiation. We study in detail the crossover between the subwavelength regime and the geometrical-optics limit. In the subwavelength regime, r…
When propagating through periodically structured media, i. e. photonic crystals, optical waves will be modulated with the periodicity. As a result, the dispersion of waves will no longer behave as in a free space, and so called frequency band structures appear. Under certain conditions, waves may be prohibited from pr…
We present numerical measurements of the critical correlation length exponent nu in the three-dimensional fuse model. Using sufficiently broad threshold distributions to ensure that the system is the strong-disorder regime, we determine nu to be nu = 0.86 +/- 0.06 based on analyzing the fluctuations of the survival pr…
We incorporate realistic pair potential energies directly into a non-linear least-square fit of diffraction data to quantitatively compare structure models with experiment for the Ni-rich $d$(AlNiCo) quasicrystal. The initial structure models are derived from a few {\it a priori} assumptions (gross features of the Pat…
Elastic constants and zone-boundary phonon frequencies of gold are calculated by total energy electronic structure methods to twofold compression. A generalized force constant model is used to interpolate throughout the Brillouin zone and evaluate moments of the phonon distribution. The moments are used to calculate t…