Search results for "Plastics"
showing 10 items of 2724 documents
Structural Characterization of Glycoconjugate Polystyrene in Aqueous Solution
1999
Maltopentaose-carrying polystyrene was synthesized by the homopolymerization of vinylbenzyl maltopentaose amide. Resulted amphiphilc polymacromonomer was dissolved in 0.1 M urea aqueous solution, and its structure was characterized by small-angle X-ray scattering and molecular modeling. Maltopentaose-carrying polystyrene polymacromonomer was found to be represented by a molecular bottlebrush, composed of a large helix of polystyrene backbone and maltopentaose brushes. The molecular bottlebrush seems to be distributed randomly or many even be broken once or twice in segments with no apparent intersegmental spatial correlation. A large helix of polystyrene backbone is formed by a random seque…
The Swelling Behavior of Polyelectrolyte Multilayers in Air of Different Relative Humidity and in Water
2002
The swelling properties of physisorbed polyelectrolyte multilayer self-assemblies with alternating polyion charge in humid air and in aqueous environment were investigated via X-ray and neutron reflectometry as well as optically, using surface plasmon spectroscopy. The sorption behavior was similar to that found for neutral polymers and was related to an internal screening of the charges of the adjacent layers owing to the high entanglement of the polyelectrolyte chains and the resulting low mobility of the polymer segments. The screening was found to be incomplete only in the top layer, resulting in a net charged surface.
A simple method to prepare solid nanoparticles of water-soluble salts using water-in-oil microemulsions
2000
A new and simple method to prepare solid nanoparticles of water-soluble salts using water-in-oil microemulsions is described. In particular, starting from water/sodium bis(2-ethylhexyl)sulfosuccinate/n-heptane microemulsions carrying inside the aqueous core of the reversed micelles some water-soluble salts [CaCl2, Na2HPO4, Cu(NO3)2], after evaporation of the volatile components (water and apolar organic solvent), the resulting inorganic salt/surfactant composites were found to be totally dispersible in pure n-heptane. The presence of nanoparticles in these resuspended composites was ascertained by transmission electron microscopy observation of samples obtained by gentle evaporation of the …
Polyelectrolyte Complexes: Phase Diagram and Intrinsic Viscosities of the System Water/Poly(2-vinylpyridinium-Br)/Poly(styrene sulfonate-Na)
2012
In contrast to all earlier work on that subject, measurements are performed at high dilution up to total polymer concentrations wpol of 0.5 wt%. Aqueous solutions of poly(2-vinylpyridinium-Br) and of poly(styrene sulfonate-Na) are only fully miscible if wpol < 0.02 wt%. Decomposition into two liquid phases is observed upon an increase in wpol, where the extension of the miscibility gap is considerably larger at 60 than at 25 °C. Viscosity measurements demonstrate that the formation of the polyelectrolyte complexes may take hours. The intrinsic viscosity of the polyanion turns out to be 20 times larger than that of the polycation and to be much more sensitive toward the addition of extra sal…
Kinetic Investigation on Metal Free Anionic Polymerization of Methyl Methacrylate Using Tetraphenylphosphonium as the Counterion in Tetrahydrofuran
1997
The anionic polymerization of methyl methacrylate using tetraphenylphosphonium triphenylmethanide as an initiator proceeds in a living manner even at room temperature. The rate constants of propagation were measured between -20 and +20 °C using a flow tube reactor. At 0 °C the reaction half-lives range from 0.3 to 1 s. The polymerization follows first-order kinetics with respect to monomer conversion (with a short induction period) and shows a linear dependence of the number-average degree of polymerization on conversion with high initiator efficiencies and narrow molecular weight distributions (M w /M n < 1.1). The dependence of the measured rate constants on the active center concentratio…
Temperature and light sensitive copolymers containing azobenzene moieties prepared via a polymer analogous reaction
2009
Abstract Four different series of polyacrylamides containing different amounts of azobenzene moieties have been synthesized via a polymer analogous reaction of poly(pentafluorophenylacrylate) (PPFPA). All copolymers were designed to exhibit a lower critical solution temperature (LCST) in aqueous solution, which was dependent on (i) the amount of incorporated chromophoric azobenzene groups and (ii) the isomerization state of the respective azobenzene group. Higher LCST values were measured for UV-irradiated solutions of the copolymers in comparison to the non-irradiated copolymer solutions. A maximum difference in the LCST of up to 7 °C was found for the copolymer poly(N,N-dimethylacrylamide…
Treatment of poly(styrene-co-methacrylic acid)/poly(4-vinylpyridine) blends in solution under liquid–liquid phase-separation conditions. A new method…
2006
Phase diagrams are contributed for polymer mixture systems in solution. One polymer has proton-acceptor character and the other has growing proton-donor nature, which is reflected in the phase diagrams. Usually, these diagrams are obtained from size-exclusion chromatographic (SEC) measurements. A totally novel application, which is exposed in this report, is the construction of the phase diagram from the viscometric experiments of polymer mixtures. The evaluated binodal or cloud-point isotherms so built agree well with those from SEC. The results indicate an augmentation in the dimensions of donor polymer B, in the presence of acceptor polymer C, intensifying with the concentration of C, wh…
Calculation of phase diagrams not requiring the derivatives of the Gibbs energy for multinary mixtures
1996
A method for the calculation of phase diagrams (tie lines and binodal, spinodal, critical points and their stability) based exclusively on the Gibbs energy of mixing with no need of its derivatives with respect to the composition variables is extended to multinary mixtures for any number of components. The mathematical description of the (K-1)-dimensional phase diagram of a K-component mixture is presented. The method is demonstrated for a quinternary blend of five polymers exhibiting a closed miscibility gap; all binary, ternary and quaternary subsystems are completely miscible. The phase separation in the quinternary system is caused by very favorable interactions in the ternary subsystem…
Novel Polycaprolactone Nanocomposites Containing Thymol of Interest in Antimicrobial Film and Coating Applications
2008
It is well-known that the nanocomposites technology can significantly enhance, among others, the thermal, mechanical, and barrier properties of plastics. It is also known that most bioplastics, including the thermoplastic biopolymers, have lower than desired levels for certain properties which makes their use in certain packaging applications problematic. The combination of active technologies such as antimicrobials and nanotechnologies such as nanocomposites can synergistically lead to bioplastic formulations with balanced properties and functionalities for their implementation in packaging applications. The present work presents the development and characterization of novel nanocomposite…
Aminofunctional polyethers: smart materials for applications in solution and on surfaces
2013
In recent years, biocompatible polyethers with multi-aminofunctionality have been used for a variety of applications in different fields. Both established and recently developed synthesis strategies for such polymers and applications as stimuli-responsive materials, non-viral vectors, shell crosslinked micelles and for surface functionalization are reviewed. The intriguing potential of such materials is due to both polyether and polyamine components and can thus be readily tuned by the copolymer microstructure and composition. © 2013 Society of Chemical Industry