Search results for "Hydrodynamic radius"
showing 10 items of 35 documents
VORTEX LAYERS IN THE SMALL VISCOSITY LIMIT
2006
In this paper we suppose that the initial datum for the 2D Navier–Stokes equations are of the vortex layer type, in the sense that there is a rapid variation in the tangential component across a curve. The variation occurs through a distance which is of the same order of the square root of the viscosity. Assuming the initial as well the matching (with the outer flow) data analytic, we show that our model equations are well posed. Another necessary assumption is that the radius of curvature of the curve is much larger than the thickness of the layer.
Quasi-elastic light scattering in polymer-containing microemulsion
1996
Abstract Quasi-elastic light scattering (QELS) was performed in dilute water in oil microemulsion stabilized by AOT surfactant. The water-soluble polyethylene oxide (PEO) with low molecular weight (8000) added to the microemulsion seems to be confined within the aqueous microphase, since PEO is insoluble in oil (n-heptane). The measurements by QELS of diffusion coefficient, at dilute concentrations, allow determination of the size of the droplets. The phase diagram of the microemulsion undergoes remarkable changes on addition of the polymer. The results show that at fixed R ( water surfactant ratio) the droplets decrease their size as the concentration of polymer increases. This occurrence …
A Facile Approach for Transferring Hydrophobic Magnetic Nanoparticles into Water-Soluble Particles
2008
A novel, easy and high-efficient method is described for transferring hydrophobic magnetic Fe 3 O 4 nanoparticles from organic to aqueous solution by wrapping a thermo-responsive and photocrosslinkable poly(N-isopropylacrylamide) (PNIPAm) terpolymer around the particles. The wrapping procedure is introduced by the co-nonsolvent transition of PNIPAm in the mixing solvent and the polymer can dissolve in water carrying Fe 3 O 4 nanoparticles by noncovalent interaction. The temperature-dependant and magnetic properties of the water-soluble particles are characterized in this paper.
Effects of isotopic substitution on the conformational properties of polymeric aqueous solutions
2000
Abstract This work deals with a side-by-side comparison between the PEO conformational properties in H 2 O and D 2 O. The gyration radius, evaluated by SANS, the hydrodynamic radius, evaluated by PCS, and the Raman D-LAM band analysis furnish valuable information on the structural arrangement of the molecules. The findings clearly show different behavioural properties of the polymer in H 2 O and D 2 O.
Complex Formation of DNA with Oppositely Charged Polyelectrolytes of Different Chain Topology: Cylindrical Brushes and Dendrimers
2007
The complex formation between DNA (pUC19-supercoiled DNA, 2686 base pairs) and some polycations of different chain topologies in aqueous solution was studied by light scattering, gel electrophoresis, and AFM. The investigated polycations comprised cylindrical brush polymers with quaternized poly(vinylpyridine) and polyethylene imine side chains as well as a fifth generation dendrimer thus covering a broad molar mass regime of 3 × 104 g mol-1 < Mw < 1 × 107 g mol-1 and very different chemical charges/molecule, Z+, of 127 < Z+ < 5500. Irrespective of the polycation, the complexes formed in dilute solution exhibited a similar size in terms of the mean square radius of gyration, 〈Rg2〉, i.e., 30…
The influence of hydrophobic substitution on self-association of poly(ethylene oxide)-b-poly(n-alkyl glycidyl carbamate)s-b-poly(ethylene oxide) trib…
2007
Abstract A series of amphiphilic poly(ethylene oxide)-b-poly(n-alkyl glycidyl carbamate)s-b-poly(ethylene oxide) triblock copolymers were synthesized by reaction between poly(ethylene oxide)-b-polyglycidol-b-poly(ethylene oxide) precursor copolymer and four n-alkyl isocyanates: ethyl, propyl, butyl and pentyl. After dissolution in water at room temperature the copolymers spontaneously form micelles. The critical micellization concentrations were determined by UV–VIS spectroscopy. The dimensions of the micelles, the aggregation numbers, and in some cases the micellar shape were determined by dynamic and static light scattering in a relatively broad temperature range. Special attention has be…
Collapse of Linear Polyelectrolyte Chains in a Poor Solvent: When Does a Collapsing Polyelectrolyte Collect its Counterions?
2008
To better understand the collapse of polyions in poor solvent conditions the effective charge and the solvent quality of the hypothetically uncharged polymer backbone need to be known. In the present work this is achieved by utilizing poly-2-vinylpyridine quaternized to 4.3% with ethylbromide. Conductivity and light scattering measurements were utilized to study the polyion collapse in isorefractive solvent/nonsolvent mixtures consisting of 1-propanol and 2-pentanone, respectively, at nearly constant dielectric constant. The solvent quality of the uncharged polyion could be quantified which, for the first time, allowed the experimental investigation of the effect of the electrostatic intera…
Statistical properties of linear-hyperbranched graft copolymers prepared via "hypergrafting" of AB(m) monomers from linear B-functional core chains: …
2015
The reaction of ABm monomers (m = 2, 3) with a multifunctional Bf-type polymer chain ("hypergrafting") is studied by coarse-grained molecular dynamics simulations. The ABm monomers are hypergrafted using the slow monomer addition strategy. Fully dendronized, i.e., perfectly branched polymers are also simulated for comparison. The degree of branching of the molecules obtained with the "hypergrafting" process critically depends on the rate with which monomers attach to inner monomers compared to terminal monomers. This ratio is more favorable if the ABm monomers have lower reactivity, since the free monomers then have time to diffuse inside the chain. Configurational chain properties are also…
Cylindrical Polymer Brushes with Elastin-Like Polypeptide Side Chains
2013
Monodisperse high molar mass elastin-like polypeptide macromonomers comprising 20 pentasequences (M = 8332 g/mol) were radically polymerized to high degrees of polymerization Pw = 590. Polymerization was conducted in water well above the lower phase transition temperature, i.e., in the phase separated regime. The resulting polymers adopt a cylindrical shape as demonstrated by AFM pictures of solutions spin-cast on mica. The directional persistence of the cylindrical brushes was determined by static light scattering to Kuhn statistical segments lengths lk = 120 nm at 5 mM aqueous NaCl solution which decreased to lk = 54 nm at 0.65 M NaCl. Upon polymerization the phase transition temperature …
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…