Search results for "Amide"
showing 10 items of 3119 documents
Cooperative supramolecular polymerization and amplification of chirality in C3-symmetrical OPE-based trisamides.
2011
Sergeants-and-soldiers experiments demonstrate the amplification of chirality that transforms the racemic mixture of helical columns formed from OPE-based trisamides into enantiomerically enriched helical structures (see scheme).The cooperative supramolecular polymerization of the trisamides is investigated by theoretical calculations and temperature-dependent UV/Vis and CD experiments. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Novel acrylamido monomers with higher hydrophilicity and improved hydrolytic stability: III. DNA separations by capillary electrophoresis in poly(N-a…
1996
Separation of DNA fragments in a novel polymer network, consisting of N-acryloylaminopropanol (AAP) is reported. The performance of this novel monomer, as a sieving liquid polymer in capillary zone electrophoresis, was evaluated. In 50 microns ID capillaries, an 8% solution of poly (AAP) can afford apex-resolution of the 123/124 bp adjacent pair of DNA fragments in marker V, typically unresolved in any poly (acrylamide) formulation. It is proposed that the distal-OH group in the AAP molecule can form transient H-bonds with the DNA double helix. Molecular modeling shows a meandering structure for poly (AAP), lacing the walls of half a cylinder, with kinks protruding at regular intervals, pot…
EFFECT OF MOISTURE ON THE BULK PROPERTIES OF SALTED POLY(CAPROAMIDE).
1980
The glass-transition temperature (Tg) and the elastic modulus of nylon-6 and its mixtures with 4% w/w LiCl and with 2% LiCl+3% LiBr were investigated. In one set of experiments care was taken to avoid absorption of moisture during the measurements. In another set of experiments, samples were exposed to atmospheric humidity for different lengths of time. Both unoriented and oriented specimens were investigated. The presence of 4% LiCl almost doubles the amount of moisture absorbed at equilibrium by nylon-6. The Tg was found to be greatly affected by the moisture content and by salt type. When strict precautions to exclude moisture are taken, the addition of 4% LiCl raises the Tg of nylon-6 b…
Chain Stiffness of Elastin-Like Polypeptides
2010
The hydrodynamic radii of a series of genetically engineered monodisperse elastin like polypeptides (ELP) was determined by dynamic light scattering in aqueous solution as function of molar mass. Utilizing the known theoretical expression for the hydrodynamic radius of wormlike chains, the Kuhn statistical segment length was determined to be lk = 2.1 nm, assuming that the length of the peptide repeat unit was b = 0.365 nm, a value derived for a coiled conformation of ELP. The resulting chain stiffness is significantly larger than previously reported by force-distance curve analysis (lk < 0.4 nm). The possible occurrence of superstructures, such as hairpins or helices, would reduce the conto…
The uptake of N-(2-hydroxypropyl)-methacrylamide based homo, random and block copolymers by human multi-drug resistant breast adenocarcinoma cells
2009
A series of well-defined, fluorescently labelled homopolymers, random and block copolymers based on N-(2-hydroxypropyl)-methacrylamide were prepared by reversible addition–fragmentation chain transfer polymerization (RAFT polymerization). The polydispersity indexes for all polymers were in the range of 1.2–1.3 and the number average of the molar mass (Mn) for each polymer was set to be in the range of 15–30 kDa. The cellular uptake of these polymers was investigated in the human multi-drug resistant breast adenocarcinoma cell line MCF7/ADR. The uptake greatly depended on the polymer molecular mass and structure. Specifically, smaller polymers (approx. 15 kDa) were taken up by the cells at m…
Continuous polymer fractionation of polysaccharides using highly substituted trimethylsilylcellulose
1998
Trimethylsilylcellulose (TMSC) was prepared from commercial cellulose with a mixture of hexamethyldisilazane and chlorotrimethylsilane in the solvent system N,N-dimethylacetamide/lithium chloride. The soluble, highly silylated polymer (degree of substitution, DS 2.9) had a molar mass M, of 500 kg/mol and a molecular non-uniformity U = (M w /M n )- 1 of 2.9. In order to investigate the principal suitability of a continuous polymer fractionation for polysaccharides like cellulose derivatives and to obtain TMSC with different molecular weights and lower non-uniformity TMSC was fractionated by means of CPF (Continuous Polymer Fractionation), well-established in the field of synthetic polymers. …
Experimental design approach in the synthesis of molecularly imprinted polymers specific for iprodione fungicide
2015
International audience; An experimental design (ED) approach was applied to study the weight of three factors in the synthesis of a molecularly imprinted polymer (MIP) specific for iprodione fungicide. The objective was to obtain a high specific polymer with the best performance of iprodione binding. Thirteen iprodione-imprinted polymers and 13 non-imprinted polymers (NIP) were synthesized according to ED having 3 influencing factors: the polymerization method, the crosslinker nature and the functional monomer type. For each factor, two levels were studied: bulk and precipitation polymerization for the first factor, trimethylolpropane trimethacrylate (TRIM) and ethylene glycol dimethacrylat…
N-Methyldehydroamino acids promote a configuration cis of N-methylamide bond
2008
Abstract Dehydroamino acids with a methylated N-terminal tertiary amide bond occur in natural small cyclic peptide toxins. To investigate their conformational preferences a systematic theoretical analysis was performed on N ′-methylamides of N -acetyl- N -methyldehydroamino acids (Ac-Δ(Me)Xaa-NHMe, where Xaa = ( Z )-Abu, ( E )-Abu, Val, ( Z )-Phe, and ( E )-Phe) considering the configuration trans and cis of the tertiary amide bond. The ϕ , ψ potential energy surfaces were calculated at the B3LYP/6-31+G ∗∗ //HF/3-21G level with inclusion of the solvent (water) effect (SCRF method). The conformers localised were fully optimised at the B3LYP/6-31+G ∗∗ in vacuo. The accessible areas of the pot…
The role of organoclay in promoting co-continuous morphology in high-density poly(ethylene)/poly(amide) 6 blends
2008
The effect of organically modified clay on the morphology, rheology and mechanical properties of high-density polyethylene (HDPE) and polyamide 6 (PA6) blends (HDPE/PA6 ¼ 75/25 parts) is studied. Virgin and filled blends were prepared by melt compounding the constituents using a twin-screw extruder. The influence of the organoclay on the morphology of the hybrid was deeply investigated by means of wide-angle X-ray diffractometry, transmission and scanning electron microscopies and quantitative extraction experiments. It has been found that the organoclay exclusively places inside the more hydrophilic polyamide phase during the melt compounding. The extrusion process promotes the formation o…
Enhancing the mechanical performance of polymer based nanocomposites by plasma-modification of nanoparticles
2012
Abstract The possibility of enhancing the mechanical performance of two different polymer-based nanocomposites using polyamide 6 (PA6) and poly[ethylene-co-(vinyl acetate)] (EVA) as matrices was investigated. The nanofillers used were, respectively, either carbon nanotubes (CNTs) or an organically modified montmorillonite (Cloisite 15A), both previously modified by plasma treatment to introduce polar moieties. The nanofillers were fully characterized by Raman spectroscopy, XPS, FT-IR and XRD, demonstrating their effective modification with oxygenated groups. The nanocomposites were prepared by melt processing in order to obtain films and fibres. The mechanical tests carried out on the nanoc…