Nanoassemblies with light‐responsive size and density from linear flexible polyelectrolytes

This study presents electrostatically self‐assembled nanoparticles from linear flexible polyelectrolytes (poly(diallyldimethylammonium chloride or quarternized poly(4‐vinylpyridine)) and an ionic photo‐isomerizable azo dye (Acid Yellow 38) that can change their size upon UV‐light irradiation. Assemblies with narrow size distribution are stable in aqueous solution. For samples with under‐stoichiometric dye load, UV‐light exposure triggers a size decrease, e.g. from a hydrodynamic radius of R_h = 94 nm to R_h = 62 nm for an Ay38‐PDADMAC sample with a charge ratio of l_charge = 0.7. Size changes are caused by trans‐cis isomerization of the dye, accompanied by a change in hydrophilicity, binding enthalpy and entropy. Assemblies are characterized by static and dynamic light scattering, atomic force microscopy, UV–vis spectroscopy and isothermal titration calorimetry. Zeta potential measurements give insight into the electrostatic stabilization and size‐control of the ionic nano‐assemblies, revealing a master curve of effective surface charge density versus hydrodynamic radius. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys., 2013     

Excitation of the Characteristic K Series Radiation,Coherent and Incoherent Scatter of Low Energy Gamma Rays

On the basis of a simplified mathematical model there is calculated the probability of a photon of characteristic K series radiation excited by a photon of low energy gamma radiation hitting the detector. There are also included the probabilities for coherently and incoherently scattered primary radiation considering electron binding energies.     

Side chain length affects backbone dynamics in poly(3‐alkylthiophene)s

Charge transport in conjugated polymers may be governed not only by the static microstructure but also fluctuations of backbone segments. Using molecular dynamics simulations, we predict the role of side chains in the backbone dynamics for regiorandom poly(3‐alkylthiophene‐2,5‐diyl)s (P3ATs). We show that the backbone of poly(3‐dodecylthiophene‐2‐5‐diyl) (P3DDT) moves faster than that of poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) as a result of the faster motion of the longer side chains. To verify our predictions, we investigated the structures and dynamics of regiorandom P3ATs with neutron scattering and solid state NMR. Measurements of spin‐lattice relaxations (T₁) using NMR support our prediction of faster motion for side chain atoms that are farther away from the backbone. Using small‐angle neutron scattering (SANS), we confirmed that regiorandom P3ATs are amorphous at about 300 K, although microphase separation between the side chains and backbones is apparent. Furthermore, quasi‐elastic neutron scattering (QENS) reveals that thiophene backbone motion is enhanced as the side chain length increases from hexyl to dodecyl. The faster motion of longer side chains leads to faster backbone dynamics, which in turn may affect charge transport for conjugated polymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1193–1202     

Multiarm star triblock terpolymers via sequential double click reactions

Multiarm star triblock terpolymers were obtained by using two different click reactions sequentially: Cu(I) catalyzed azide–alkyne and Diels–Alder. The synthetic strategy is described as follows: (poly(methyl methacrylate))_n‐(polystyrene)_m‐poly(divinyl benzene)) ((PMMA)_n‐(PS)_m‐polyDVB) multiarm star diblock copolymer was first obtained from an azide–alkyne click reaction of (alkyne‐PS)_m‐polyDVB multiarm star polymer with α‐anthracene‐ω‐azide PMMA (anth‐PMMA‐N₃), followed by a Diels–Alder click reaction of the anthracene groups at the star periphery with α‐maleimide poly (tert‐butyl acrylate) (PtBA‐MI) or α‐maleimide poly(ethylene glycol) (PEG‐MI) leading to target (PtBA)_k‐(PMMA)_n‐(PS)_m‐polyDVB and (PEG)_p‐(PMMA)_n‐(PS)_m‐polyDVB multiarm star triblock terpolymers. The hydrodynamic diameter of individual multiarm star triblock terpolymers were measured by dynamic light scattering (DLS) to be ～24–27 nm in consistent with the atomic force microscopy (AFM) images on silicon substrates. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1557–1564, 2010     

Optical characterization of polycarbonate: Influence of additives on optical properties

In laser transmission welding of thermoplastics the optical properties of the joining parts determine the quality of the welding result. Especially, the scattering of laser radiation in the transparent welding part has an impact on weld seam properties. This scattering is caused by additives. For polycarbonate (PC) with different additives the transmittance, the reflectance and the collimated transmittance are measured with a UV‐VIS‐NIR spectrometer. From this data, the optical properties, such as scattering coefficient, absorption coefficient, and anisotropy factor are calculated. The calculations are made with the aid of the four‐flux model of radiation transport in the diffusive approximation. The results show that the additives have a significant influence on the scattering coefficient. For most additives under consideration the scattering is forward directed, which means that most of the radiation is transmitted into the absorbing welding part. However, the power density distribution of the transmitted radiation may differ significantly from PC without additives. So, the weld seam may also differ due to different additives. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 451–455, 2010     

ELASTIC CALCULATION OF STRESSES IN RINGS USING AIRY STRESS FUNCTION

Stress calculation formulae for a ring have been obtained by using Airy stress function of the plane strain field with the decomposition of the solutions for normal stresses of Airy biharmonic equation into two parts when it is loaded under two opposite inside forces along a diameter. One part should fulfill a constraint condition about normal stress distribution along the circumference at an energy valley to do the minimum work. Other part is a stress residue constant. In order to verify these formulae and the computed results, the computed contour lines of equi-maximal shear stresses were plotted and quite compared with that of photo-elasticity test results. This constraint condition about normal stress distribution along circumference is confirmed by using Greens’ theorem. An additional compression exists along the circumference of the loaded ring, explaining the divorcement and displacement of singularity points at inner and outer boundaries.     

A proof of Price's Law on Schwarzschild black hole manifolds for all angular momenta

Price's Law states that linear perturbations of a Schwarzschild black hole fall off as t−2?−3 for t→∞ provided the initial data decay sufficiently fast at spatial infinity. Moreover, if the perturbations are initially static (i.e., their time derivative is zero), then the decay is predicted to be t−2?−4. We give a proof of t−2?−2 decay for general data in the form of weighted L¹ to L^∞ bounds for solutions of the Regge–Wheeler equation. For initially static perturbations we obtain t−2?−3. The proof is based on an integral representation of the solution which follows from self-adjoint spectral theory. We apply two different perturbative arguments in order to construct the corresponding spectral measure and the decay bounds are obtained by appropriate oscillatory integral estimates.     

Partial identification of the potential from phase shifts

We consider the three-dimensional inverse scattering with fixed energy in the spherically symmetrical case. We give a characterization of the sequences of phase shifts for two potentials which can be different only in a ball of radius a. In other words we study how the large distance interaction influences the asymptotical behavior of the phase shifts. We also characterize the tail of the potential by the growth order of the scattering amplitude F(t) for large t.     

Recent results from HERA

After the end of data taking in 2007, the experiments H1 and ZEUS have entered into an intense phase of data analysis. Recent results of this effort on neutral (NC) and charged current (CC) cross sections at high Q2, the longitudinal structure function Fl, inclusive diffraction, heavy flavour production and on searches for glueballs are presented. Also shown are results of a combined analysis on inclusive NC and CC cross sections performed by H1 and ZEUS using HERA-I data.     

Preparation of glycopolymer‐coated magnetite nanoparticles for hyperthermia treatment

In this article, magnetite nanoparticles (MNPs) coated with glycopolymer bearing glucose moieties were designed with optimal structural, colloidal, and magnetic properties for biomedical applications. MNPs with an average size of 17 ± 2 nm were synthesized by thermal decomposition process and then their surfaces were modified with active vinyl groups. Two different monomers were immobilized onto the surfaces: dopamine methacrylamide, a monomer with properties inspired on mussels adhesive capacity, or unprotected glycomonomer, 2‐{[(D ‐glucosamin‐2N‐yl)carbonyl]‐oxy}ethyl methacrylate. Afterward, the glycomonomer were polymerized at the interface of both vinyl functionalized MNPs by conventional radical polymerization. The resultant hybrid NPs were water dispersible presenting good stability in aqueous solution for long time periods. Moreover, the high density of carbohydrates at the surface of the magnetic NPs could confer targeting properties to the system as demonstrated by studies of their binding interactions with lectins, where the binding activity is higher as the glycopolymer content augments. The magnetic and magneto‐thermal properties of the synthesized hybrid NPs were evaluated. The magnetization curves reveal superparamagnetic features at 300 K, with high values of saturation magnetization. Furthermore, the hybrid glycoparticles show suitable heat dissipation power when exposed to alternating magnetic field conditions. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012