Search results for "Chain length"
showing 10 items of 54 documents
Polymer support synthesis
1989
Non-porous silica gel microbeads of diameter 1.5 microns have been investigated as supports for oligonucleotide synthesis. In the preparation of oligothymidylates of chain length up to 150 bases, with 5'-di-p-anisylphenylmethyl-3'-phosphoramidite as an intermediate, the average yields per chain elongation were up to 99%. Lower overall yields were observed in the case of a support which developed a strong tendency towards aggregation after the build up of an oligonucleotide coating.
Isoniazid cocrystallisation with dicarboxylic acids: vapochemical, mechanochemical and thermal methods
2016
Cocrystallisation with a series of related compounds allows for the exploration of trends and limitations set by structural differences between these compounds. In this work, we investigate how the length of a dicarboxylic acid influences the outcome of cocrystallisation with isoniazid. We have performed a systematic study on the mechanochemical, thermal and solvent vapour-assisted cocrystallisation of aliphatic dicarboxylic acids (C3–C10) with isoniazid. Our results demonstrate that the rate of mechanochemical and vapour-assisted cocrystallisation depends on the acid chain length and shows alternation between odd- and even-chain acids. The results of thermal cocrystallisation showed that t…
Solute retention in reversed-phase chromatography as a function of stationary phase properties: Effect of n-alkyl chain length and ligand density
1988
Two series of bonded phases were synthesized employing LiChrospher Si 100, 10 μm and n-alkyldimethylmonochlorosilanes as silanizing reagents. In series A the n-alkyl chain length, n, of the bonded phase was varied between 1 and 20 at a constant ligand density of 3.5±0.2μmol·m−2. In series B the ligand density, d, was gradually changed from 0 to 4.1μmol·m−2 on the C1, C4, C6, C8 and C18 bonded phases, respectively.
Entropic Unmixing in Nematic Blends of Semiflexible Polymers.
2020
Binary mixtures of semiflexible polymers with the same chain length, but different persistence lengths, separate into two coexisting different nematic phases when the osmotic pressure of the lyotropic solution is varied. Molecular Dynamics simulations and Density Functional Theory predict phase diagrams either with a triple point, where the isotropic phase coexists with two nematic phases or a critical point of unmixing within the nematic mixture. The difference in locally preferred bond angles between the constituents drives this unmixing without any attractive interactions between monomers.
Interaction of polyribosomal components and polyribonucleotides with microtubule proteins
1982
To demonstrate the affinity of RNA-containing polyribosomal components (isolated from L5178y cells) to microtubules, microtubule protein was attached to an insoluble matrix. In contrast to ribosomes, poly(A) (+) mRNA and poly(A)-RNP were found to bind to the matrix. Using synthetic polyribonucleotides, no significant differences in the binding properties of single- and double stranded polymers of different base composition to microtubule protein were observed. However, binding is dependent on the size of the polymer; a minimal chain length of 12 nucleotide units is required.
Thermodynamics of Aqueous Poly(ethylene oxide)−Poly(propylene oxide)−Poly(ethylene oxide)/Surfactant Mixtures. Effect of the Copolymer Molecular Weig…
2004
A calorimetric study was performed to focus attention on the interactions between copolymers and anionic surfactants in aqueous solutions. Three aspects were analyzed: (1) the hydrophobicity of the surfactant, (2) the change of the copolymer molecular weight, and (3) the nature of the hydrophilicity of the copolymer. To this purpose, the family of sodium alkanoates (sodium octanoate through sodium dodecanoate) and the triblock copolymers EO76PO 29EO76 (F68), EO103PO39EO 103 and EO132PO50EO132 were investigated. Comparing F68 and EO13PO30EO13 (L64), previously studied by us, provided information on the effect of the copolymer hydrophilicity. The experimental data were analyzed by means of a …
Static and Dynamic Properties of Adsorbed Chains at Surfaces: Monte Carlo Simulation of a Bead-Spring Model
1996
The adsorption of flexible polymers from dilute solution in good solvents at attractive walls is studied by Monte Carlo simulation of a coarse-grained off-lattice model, varying chain length N and ...
Effective conjugation in conjugated polymers with strongly twisted backbones: A case study on fluorinated MEHPPV
2016
Conjugated polymers with strongly twisted backbones, such as MEHPPV with fluorinated vinylene units (F-MEHPPV), demand a redefinition of the all-important ‘effective conjugation length’ ECL, which we extract here by a facile graphical method. In MEHPPV (being essentially planar), the ECL coincides with the ‘maximum conducive chain length’ MCC and extends over about n ≈ 9 repetition units (RU). In F-MEHPPV, the MCC is similarly long with n ≈ 8, but the ECL localizes on just one RU. The strong twist in F-MEHPPV persists in the excited state, broadening the emission spectrum and quenching the fluorescence with reduced radiative and enhanced non-radiative rates.
Über Molekulargewichte und Molekulargewichtsverteilungen nativer Cellulosen
1954
Ziel der vorliegenden Arbeit ist die Bestimmung der Grose und der Grosenverteilung der im nativen Pflanzenmaterial vorliegenden glukosidischen Ketten der Cellulose. Zur Gewinnung dieser Ketten wird das Pflanzenmaterial einer Extraktion mit organischen Losungsmitteln und mit 2%iger Natronlauge unterworfen und anschliesend polymeranalog nitriert. Die einzelnen Schritte des praparativen Verfahrens werden im Hinblick auf ihre mogliche Abbauwirkung durch Variation samtlicher Versuchsbedingungen kontrolliert. Es wird gezeigt, das das angewandte Verfahren die ursprunglich vorhandene Kett enlange und Kettenlangenverteilung weitgehend unverandert last. Die Bestimmung des Polymerisationsgrades erfolg…
Structure and properties ofn-alkyldimethylsilyl bonded silica reversed-phase packings
1978
Summary The effects of the modifier functionality and the chain length ofn-alkylchlorosilanes on the surface structure of packings and on their retention behaviour in reversed-phase chromatography were investigated. Comparative retention studies on three silica packings that had been treated to maximum conversion withn-octyltrichlorosilane (I),n-octylmethyldichlorosilane (II) andn-octyldimethylmonochlorosilane (III) showed that the most pronounced reversed-phase character is obtained by using III as the modifying reagent. A series ofn-alkyldimethylsilyl bonded silica packings were prepared with widely differingn-alkyl chain lengths. Although the packings are very hydrophobic, the maximum su…