Search results for "polymers"

Role of organo-modifier and metal impurities of commercial nanoclays in the photo-and thermo-oxidation of polyamide 11 nanocomposites

2020

The photo-oxidative degradation processes of bio-based PA11 nanocomposites containing montmorillonite (MMT) and the organo-modified Cloisite&reg

Physicochemical investigation of cobalt?iron cyanide nanoparticles synthesized by a novel solid?solid reaction in confined space

2004

Cobalt–iron cyanide (Cox[Fe(CN)6]) nanoparticles have been synthesized by a novel solid–solid reaction in the confined space of dry sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reversed micelles dispersed in n-heptane. The reaction has been carried out by mixing two dry AOT/n-heptane solutions containing CoCl2 and K4Fe(CN)6 or K3Fe(CN)6 nanoparticles in the micellar core, respectively. By UV-Vis spectroscopy it was ascertained that, after the mixing process, the formation of stable nanoparticles is fast and complete. Microcalorimetric measurements of the thermal effect due to the Cox[Fe(CN)6] nanoparticle formation allowed the determination of the stoichiometric ratio (x) and of the molar e…

FT-IR investigation of the acetamide state in AOT reversed micelles

2003

The state of acetamide nanoparticles encapsulated in the hydrophilic core of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reversed micelles and dispersed in CCl4 has been investigated by Fourier transform infrared spectroscopy. The analysis of the vibrational spectra reveals even at the higher acetamide to AOT molar ratio some changes of the typical H-bonded structure of solid acetamide ascribable to their small size, confinement effects, and acetamide-AOT head group interactions. The stretching modes of acetamide CO and AOT sulfonate groups indicate unambiguously specific acetamide-AOT head group interactions.

Calorimetric and Volumetric Investigations of the Effect of the Hydrophobicity of the Surfactant on the Binding between (Ethylene oxide)13-(propylene…

2004

The enthalpy and the volume of transfer (DeltaY(t)) of the unassociated (ethylene oxide)(13)-(propylene oxide)(30)-(ethylene oxide)(13) (L64) from water to the aqueous sodium alkanoate solutions as functions of the surfactant concentrations (m(S)) were determined at 298 K. The surfactants studied are sodium hexanoate, sodium heptanoate, sodium octanoate, sodium undecanoate, and sodium dodecanoate. As a general feature, for the short alkyl chain surfactants, DeltaY(t) describes an S-shaped curve in the range of m(S) analyzed whereas for the more hydrophobic surfactants the DeltaY(t) vs m(S) trends exhibit maxima which appear at ms values very close to the critical micellar concentration in w…

THE MAGNETIC SUSCEPTIBILITY OF MOLTEN NICKEL(II) COMPLEXES

1957

Abstract The bis-( N -alkylsalicylaldimine) - nickel (II) complexes, which are diamagnetic in the solid state, become paramagnetic with moments ranging from 0.8 to 1.15 B.M. in the molten state.

Kinetic analysis of "living" polymerization processes exhibiting slow equilibria. 6. Cationic polymerization involving covalent species, ion pairs, a…

1996

The kinetics of cationic polymerization is studied theoretically in accordance with a three-state mechanism which consists of two successive equilibria:  the ionization/ion collapse equilibrium between covalent species and ion pairs, and the subsequent dissociation/association equilibrium between ion pairs and free ions. The number- and weight-average degrees of polymerization and the polydispersity index (PDI), Pw/Pn, are derived. The molecular weight distribution of the polymer generated from this mechanism is generally broader than that of polymers formed via a two-state mechanism, i.e. with only one equilibrium either between covalent species and ion pairs or between covalent species an…

Reaction of α,β-poly(N-hydroxyethyl)-DL-aspartamide with derivatives of carboxylic acids

1987

The comparative spreading behavior of enantiomeric and racemic tyrosine amphiphiles

1985

Several derivatives of tyrosine or its methyl ester have been synthesized in which the para hydroxyl group on the aromatic side chain has been converted to a long chain alkyl ether or urethane. The surface behavior of these compounds is discussed. Enantiomeric discrimination, the ability of a chiral molecule to distinguish between mirror-image stereoisomers, has been investigated for the urethane derivates by comparing the surface pressure-area isotherms of the enantiomer with that of the racemic compound. Enantiomeric discrimination was demonstrated for the methyl ester analog, but was not conclusively observed for the zwitterionic compounds. Possible structural requirements for enantiomer…

Orientation, recognition, and photoreaction of nucleolipids in model membranes

1990

Amphiphiles with nucleobases and nucleosides as headgroups have been synthesized. Their surface behavior was investigated in monolayers at the air/water interface. The double chain nucleolipids form stable monolayers with nearly identical surface pressure-area diagrams, whereas the spreading behavior of the mono chain amphiphiles is dominated by the various nucleobase-headgroups. When measuring the interactions between nucleolipid monolayers and nucleobases (monomeric and polymeric ones), specific base-base effects could be observed: the complementary nucleobases solubilized in the subphase expand the monolayer more than the non-complementary ones. Photodimerization reactions of thymine-amp…

Prospective Cancer Therapies Using Stimuli‐Responsive DNA Nanostructures

2021

Financial support by the Emil Aaltonen Foundation, the Sigrid Jusélius Foundation, the Magnus Ehrnrooth Foundation, Academy of Finland (grants no. 317042 and 331151), the Jane and Aatos Erkko Foundation and the Vilho, Yrjö and Kalle Väisälä Foundation of the Finnish Academy of Science and Letters is gratefully acknowledged Nanostructures based on DNA self-assembly present an innovative way to address the increasing need for target-specific delivery of therapeutic molecules. Currently, most of the chemotherapeutics being used in clinical practice have undesired and exceedingly high off-target toxicity. This is a challenge in particular for small molecules, and hence, developing robust and ef…