Surface modification of poly(tetrafluoroethylene) and poly(ethylene terephthalate) films via environmental crazing

This work addresses the phenomenon of the development of a patterned surface relief on polymer films via different modes of environmental crazing. Commercial films of semicrystalline poly(tetrafluoroethylene) (PTFE) and amorphous glassy poly(ethylene terephthalate) (PET) were subjected to tensile drawing in the presence of physically active liquid environments (carbon tetrachloride or aliphatic alcohols). The structure parameters and wettability of the modified films were studied by AFM, SEM, profilometer measurements and contact angle measurements. Environmental intercrystallite crazing of PTFE is accompanied by the development of an unstable structure with a high free surface, which experiences marked strain recovery upon unloading. As a result of the relief formation, PTFE hydrophobicity is enhanced (the water contact angle increases by 25°). Classical environmental crazing of PET films is accompanied by the formation of an anisotropic surface relief which is an assembly of crazes oriented perpendicular to the direction of tensile drawing, thus leading to the phenomenon of anisotropic wetting. The proposed approach for structural surface modification makes it possible to use the advantages of surface instability and spontaneous self‐organization of the polymer towards the development of a unique surface microrelief. © 2020 Society of Chemical Industry     

Langmuir films from antibodies based on amphiphilic polyelectrolytes

A technique for forming Langmuir films from antibodies based on an amphiphilic polyelectrolyte was developed. The physicochemical and immunochemical properties of the Langmuir films obtained were studied. The interaction of HBsAg with the films was found to be described by a model with one binding site, whereas that of HBsAg with antibodies adsorbed on a polystyrene plate, by a model with a positive cooperativity. The use of the novel Langmuir films from antibodies increases the sensitivity of the immunoenzyme assay.     

Use of the Laws of Delayed Fracture of Metallic Materials for Forecasting the Remaining Life of Structures under a Test Load

Metal Science and Heat Treatment -     

Configurational statistics of copolymers prepared by complex-radical polymerization

Radical copolymerization is considered theoretically taking into account the effect of complexing on the configurational statistics of macromolecules formed. Akinetic model has been developed that considers, apart from the ordinary addition of single monomer units to a propagating chain, the possible addition of monomer unit pairs along with a complexing agent in the form of a ternary complex. Within the framework of this model, the problem of calculating the probabilities of formation of any sequences of monomer units (taking into account their microtacticity) in a macromolecule has been rigorously solved as well as the problem of finding the composition distribution of the copolymer formed. It has been shown that this distribution is described by a conventional Gauss law and the appropriate parameters are given. Possible generalizations of the suggested approach are indicated.     

Self-diffusion of low-generation PAMAM dendrimers with hydroxyl surface groups in solutions: a general regularity

An experimental study of the self-diffusion and nuclear magnetic relaxation of poly(amidoamine) dendrimers with hydroxyl surface groups (PAMAM-OH) dissolved in methanol over a wide range of concentration (?) is reported. It is shown that experimental concentration dependences of PAMAM-OH self-diffusion coefficients (D) can be reduced to the so-called generalized ? dependence. Over macromolecular concentration range studied, the generalized concentration dependence of PAMAM-OH D coincides with analogous curve obtained for poly(allylcarbosilane) dendrimers of high generations. This result confirms the existence of common regularities of the dendritic macromolecule self-diffusion, and their independence of the individual physicochemical and structural properties of dendrimer, solvent, and features of their interactions in the given systems. The concentration dependence of the PAMAM-OH diffusion also exhibits a clear signature of an inflexible molecule.     

Regeneration of platinum-metal-based catalysts with carboxyphosphines as extractants

Separation of platinum-metal-based homogeneous catalysts was achieved by their conversion to complexes of functionalized phosphines of the general formulae R_3-n P[(CH₂) _x CO₂H)] _n , R = Me, Et, Ph,n = 1, 2, 3,x = 1, 2, and [(HO₂CCH₂)PCH₂]₂, followed by extraction of the complexes into aqueous phase. This approach to regeneration of platinum metals from reaction mixtures after carrying out homogeneously catalyzed reactions was demonstrated on 11 examples of various types of reactions with Ru, Rh, Pd, Os, Ir and Pt compounds as catalysts.     

CTmod-a toolkit for Monte Carlo simulation of projections including scatter in computed tomography

The CTmod toolkit is a set of C++ class libraries based on the CERN's application development framework ROOT. It uses the Monte Carlo method to simulate energy imparted to a CT-scanner detector array. Photons with a given angle-energy distribution are emitted from the X-ray tube approximated by a point source, transported through a phantom, and their contribution to the energy imparted per unit surface area of each detector element is scored. Alternatively, the scored quantity may be the fluence, energy fluence, plane fluence, plane energy fluence, or kerma to air in the center of each detector element. Phantoms are constructed from homogenous solids or voxel arrays via overlapping. Implemented photon interactions (photoelectric effect, coherent scattering, and incoherent scattering) are restricted to the energy range from 10 to 200keV. Variance reduction techniques include the collision density estimator and survival biasing combined with the Russian roulette. The toolkit has been used to estimate the amount of scatter in cone beam computed tomography and planar radiography.     

Magnetic Ordering of Dy3+ Ions in RbDy(WO4)2 Single Crystal

The specific heat C(T) of the monoclinic RbDy(WO ₄ ) ₂ crystal has been studied at very low temperatures 0.2T1.9 K and in magnetic fields 0H0.38 T. The Neel temperature was shown to be equal to T_N = 0.818 ± 0.005 K. The experimental value of the effective exchange parameter was obtained to be equal to J/k = – 0.798 K. The C T) dependence below Neel temperature 0.5T_N0.99T_N ) is well described by 2D Ising model, whereas in the temperature region close above T_N (1.01 T_N2T_N) it can be described by neither 2D, nor 3D Ising model. The experimental and theoretical H-T_N diagrams for field H a are in a reasonable agreement for simple quadratic lattice.