Search results for "Chain length"
showing 10 items of 54 documents
Polyelectrolytes Grafted to Curved Surfaces
1996
We present a scaling theory to describe equilibrium conformations of weakly charged polyelectrolyte molecules grafted at one end onto impermeable surfaces of various morphologies (spheres, cylinders) and of arbitrary curvature. We focus on the case of sufficiently densely grafted chains, i.e., on curved polyelectrolyte brushes. Different regimes of the behavior of curved polyelectrolyte brushes can be distinguished, depending on grafting density, surface curvature, and chain length. We present phase diagrams of the system describing these regimes and discuss the crossover conditions. We also analyze the effect of charge annealing in curved polyelectrolyte brushes.
Initiierte autoxydation von isotaktischem und ataktischem polybuten-1 in lösung
1968
Isotaktisches und ataktisches Polybuten-1 (PB) wurden bei 70,6°C in brombenzolischer Losung mit Azoisobuttersauredinitril als Initiator mit Sauerstoff oxydiert. Die oxydierten Proben wurden isoliert, und der Gehalt an Hydroperoxidgruppen wurde mit Hilfe von Triphenylphosphin bestimint. Cyclische Peroxide, die bei oxydiertem isotaktischem Polybuten 1 moglich sind, konnen nicht mit Triphenylphosphin bestimmt werden, da sie zerfallen, bevor sie mit dem Phosphin reagieren. Dies wurde an niedermolekularen Modellverbindungen uberpruft. Unter den Reaktionsbedingungen war die kinetische Kettenlange so klein (1 bis 2), das deutliche Unterschiede der Oxydation von isotaktischem und ataktischem Polybu…
Vergleichende kinetische untersuchungen über die basenkatalysierte reaktion von oligomethylen- und oligoäthylenglykolen mit phenylisocyanat
1961
Die durch Triathylamin katalysierte Reaktion von Oligomethylenglykolen und von Oligoathylenglykolen mit Phenylisocyanat in Dioxan bei 25°C wurde untersucht. Die Reaktionsgeschwindigkeit innerhalb der homologen bzw. polymerhomologen Reihe ist unter den angewandten Bedingungen unabhangig von der Kettenlange und der chemischen Struktur der Kette. The reaction of oligomethylene glycols (I) and oligooxyethylene glycols (II) with phenyl isocyanate in dioxane at 25°C. catalyzed by triethylamine was investigated. Under the applied conditions the reaction rate within the homologous and polymerhomologous series is independent of the chain length and the chemical constitution of the chain.
1985
A new Continuous Polymer Fractionation method, called CPF, is described. The polymer to be fractionated is dissolved in a solvent/non-solvent mixture, and this solution (feed) is extracted continuously by a second liquid (extracting agent), which contains the same solvent components as the feed. In the case of PVC, the fractionation was carried out with a pulsed counter current extraction apparatus and THF/water was used as solvent/non-solvent mixture. Fractionation is achieved by the fact that the molecules are distributed over the counter current phases according to their chain length; the feed leaves the column as gel and the extracting agent as sol. First some explorative experiments we…
Electrochemical behavior of layered annulenes
1985
Abstract The cyclic voltammetric behavior of a series of dimeric [14] annulenes was examined and compared with the monomer. The data suggest a signigficant degree of interaction between the annulene rings when a three-carbon chain connects them, little or no interaction with an eight-carbon chain, and weak interaction with a four-carbon chain.
Über polygermane
1986
Abstract The germylene Ph2Ge of Ph2GeHCl and Net3 inserts in excess Ph2GeHCl and forms polygermanes Cl(Ph2Ge)nH. This one-pot reaction and subsequent chlorination to Cl(Ph2Ge)nCl has been optimized. Increasing amounts of NEt3 step up the yields of higher polygermanes. The 13C NMR phenyl signals for C(ipso) shift to low field with increasing chain length. The crystal structures of Cl(Ph2Ge)3,4Cl (R = 0.072 and 0.087) have been determined. The position of Cl(Ph2Ge)4Cl is split off by disorder (main molecule 82%, side molecule 18%). Two crystallographically different molecules of the trigermane are present; the ClGe3Cl chain contains anti-gauche and gauche-gauche conformation respectively (d…
Draft genome sequence of Pseudomonas mediterranea strain CFBP 5447T, a producer of filmable medium-chain-length polyhydroxyalkanoates
2014
ABSTRACT Pseudomonas mediterranea strain CFBP 5447 T is a phytopathogenic bacterium isolated from tomato plants affected by pith necrosis disease. Moreover, its ability to produce medium-chain-length polyhydroxyalkanoates (mcl-PHAs) in culture from different carbon sources and valuable microbial products, such as cyclic lipopeptides, has been well documented. Here, we report the first draft genome sequence of this species.
Supramolecular complexes formed by dimethoxypillar[5]arenes and imidazolium salts: A joint experimental and computational investigation
2017
To gain more insights into the factors acting on the stability of complexes formed by pillar[5]arenes, we investigated the interaction of dimethoxypillar[5]arene with some 1-(n-alkyl)-3-(9-anthracenylmethyl)-imidazolium based organic salts. In particular, we used salts differing in not only the anion nature ([Cl−], [BF4−], [NTf2−] and [SbF6−]) and alkyl chain length (butyl, octyl and dodecylimidazolium derivatives), but also the presence of a hydrogenated or fluorinated tail (octyl and perfluorooctylimidazolium derivatives). Host–guest systems were analysed in solution, solid state and gas phase, using a combined approach of different techniques like fluorescence, 1H NMR, ESI-MS, DSC and DF…
Monte Carlo simulation of the glass transition in polymeric systems: Recent developments
1995
Abstract The bond fluctuation model on square and s.c. lattices is used as a coarse-grained model for flexible polymers in dense melts. Using an energy that favours long bonds, a conflict is created between the tendency of the bonds to stretch at low temperatures and packing constraints. This simple concept of ‘geometric frustration’ leads to glass transition. Both static and dynamic properties of this model are investigated by Monte Carlo simulations, paying attention to effects found by varying the cooling rate and the chain length N of the polymers. In two and three spatial dimensions an effective (cooling-rate dependent) glass transition temperature T g can be defined, where the system …