Search results for "Dynamic"

1991

Telechelic α,ω-macrozwitterions — narrowly distributed polystyrene chains oppositely charged at each end — were synthesized via anionic polymerization using direct functionalization with the initiator and the termination agent. The resulting products were purified (zwitterion content ≥ 0,95) and characterized with gel permeation chromatography, viscometry, static and dynamic light scattering and small-angle neutron scattering. In unpolar solvents as toluene, the polymeric zwitterions form clusters with molecular weights depending on concentration. In the dilute case, the clusters are relatively small and consist of approximately 8 zwitterions. The structure of these clusters is discussed by…

Critical micellization density: A small-angle-scattering structural study of the monomer-aggregate transition of block copolymers in supercriticalCO2

2000

In this paper we report a small-angle neutron-scattering investigation of micelle formation by the fluorocarbon-hydrocarbon block copolymer, polyvinyl acetate-b-poly (1,1,2,2-tetrahydroperfluoro-octyl acrylate) in supercritical CO{sub 2} (scCO{sub 2}) at 313 K. At high pressure the copolymer is in a monomeric state with a random coil structure, while at low pressure the polymer forms spherical aggregates stable in a wide range of thermodynamic conditions. By profiling pressure, a sharp monomer-micelle transition is obtained due to the tuning of the solvating ability of scCO{sub 2}. We confirm the previous finding that this aggregate-monomer transition is driven by the gradual penetration of…

Polymere ester von säuren des phosphors, 6. Ringöffnende polymerisation cyclischer phosphite und phosphonite durch michaelis-arbuzov-reaktion.–Theori…

1977

The hypothesis of Harwood and Patel, suggesting for the polymerization of 2-phenyl-1,3,2-dioxaphospholane a type of insertion reaction to explain the formation of ethylenediphosphinic ester structures besides the normal 2-hydroxyethyl(phenyl)phosphonic ester structures is extended to similar monomers and its theoretical consequences are examined. It is shown that in such a system mutual transformations between ω-hydroxyalkyl-P-acid and alkylenedi(P-acid)structures should occur, establishing a dynamic equilibrium and leading to a sort of azeotropic polymer, in which only one unique composition is kinetically stable. Equations relating to different kinetic parameters are deduced.

1986

A procedure is described for the preparation of a block copolymer with A-B-A sequences in which ω-ω′-dihydroxy-poly-(ethylene glycol) is inserted between two polymeric monoacidic chains of polycaproamide and bonded to them by means of ester links. The resulting material was characterized. The copolymer is isomorphous with the polycaproamide. Thermal treatments induce a crystalline transition γ α as in polycaproamide. The influence of the moisture content on the glass transition temperature and on the storage modulus is discussed. Ein Verfahren zur Herstellung eines Blockcopolymers mit A-B-A-Sequenzen wird beschrieben. In dem Copolymer ist ω-ω′-Dihydroxy-polyethylenglycol uber Esterbindungen…

Tin(IV), Monomethyltin(IV), and Dimethyltin(IV) Complexes with thiol sulfur and heterocyclic nitrogen donors: Molecular dynamics and structure by119S…

1995

The molecular dynamics of the complexes Sn(SPyN)4 (1), SnCl2(SPyN)2 (2), MeSn(SPy)3 (3), MeSnCl(SPyN)2 (4), Me2Sn(TCy)2 (5), Me2SnCl(TOx) (6), and Me2Sn(TUr) (7) [HSPy = 2-mercaptopyridine; HSPyN = 2-mercaptopyrimidine; HTCy = 2-thiocytosine; HTOx = 8-thioquinoline; H2TUr = 2-thiouracil] has been investigated by variable temperature 119Sn Mossbauer spectroscopy. The area under the resonant peaks has been determined as function of temperature, from which Debye temperatures and cut-off frequencies, as well as recoil-free fractions (Lamb Mossbauer factor) and mean square displacements of 119Sn, have been calculated. By fingerprint procedures on the basis of literature data, monomeric structure…

Advanced descriptors for long-range noncovalent interactions between SARS-CoV-2 spikes and polymer surfaces.

2021

The recent pandemic triggered numerous societal efforts aimed to control and limit the spread of SARS-CoV-2. One of these aspects is related on how the virion interacts with inanimate surfaces, which might be the source of secondary infection. Although recent works address the adsorption of the spike protein on surfaces, there is no information concerning the long-range interactions between spike and surfaces, experimented by the virion when is dispersed in the droplet before its possible adsorption. Some descriptors, namely the interaction potentials per single protein and global potentials, were calculated in this work. These descriptors, evaluated for the closed and open states of the sp…

Stratification in Drying Polymer–Polymer and Colloid–Polymer Mixtures

2017

Drying polymer-polymer and colloid-polymer mixtures were studied using Langevin dynamics computer simulations. Polymer-polymer mixtures vertically stratified into layers, with the shorter polymers enriched near the drying interface and the longer polymers pushed down toward the substrate. Colloid-polymer mixtures stratified into a polymer-on-top structure when the polymer radius of gyration was comparable to or smaller than the colloid diameter, and a colloid-on-top structure otherwise. We also developed a theoretical model for the drying mixtures based on dynamical density functional theory, which gave excellent quantitative agreement with the simulations for the polymer-polymer mixtures a…

Selective recognition of aromatic hydrocarbons by endo-functionalized molecular tubes via C/N-H⋅⋅⋅π interactions

2018

Abstract Molecular recognition of aromatic hydrocarbons by four endo -functionalized molecular tubes has been studied by 1 H NMR spectroscopy, computational methods, and single crystal X-ray crystallography. The binding selectivity is rationalized by invoking shape complementarity and dipole alignment. The non-covalent interactions are proved to predominantly be C/N-H⋅⋅⋅ π interactions.

Intrinsic Viscosities of Polyelectrolytes: Determination and Modeling of the Effects of Extra Salt

2011

Based on early measurements of J. J. Hermans and co-workers (D. T. F. Pals, J. J. Hermans, Recl. Trav. Chim. Pays-Bas 1952, 71, 513-520; D. T. F. Pals, J. J. Hermans, J. Polym. Sci. 1950, 5, 733-734; D. T. F. Pals, J. J. Hermans, J. Polym. Sci. 1948, 3, 897-898), the present contribution demonstrates how primary data should be evaluated in order to obtain reliable intrinsic viscosities. This procedure yields detailed information on the changes of the intrinsic viscosities and of the corresponding viscometric interaction parameters caused by an increasing salinity of water. Both quantities decline from a maximum value in the pure solvent to a minimum value, which is approached in the limit o…

Der Verteilungsraum von physikalisch gelöstem Sauerstoff in wäßrigen Lösungen organischer Substanzen / The Distribution Space of Physically Dissolved…

1976

Abstract In order to evaluate the distribution of molecular oxygen in biological systems, the oxygen solubility (ml/ml atm) at 37 °C in aqueous solutions of thirty organic substances with different concentrations was measured by the classical Van Slyke principle. The oxygen solubility always (with the exception of hemoglobin) decreases exponentially with increasing concentration of the respective substance. In all cases this behavior is described highly significant by a simple empiric exponential function, when the substance concentration as well as the oxygen solubility of pure water is given. The influence of one substance on oxygen solubility contributes additively to the over-all solubi…