Dynamical trajectories on the boundary in state space between laminar and turbulent plane channel flow-edge states-are computed for Newtonian and viscoelastic fluids. Viscoelasticity has a negligible effect on the properties of these solutions, and, at least at a low Reynolds number, their mean velocity profiles correspond closely to experimental observations for polymer solutions in the maximu...

We report the observations of dual wavelength amplified spontaneous emission from the solutions of a conjugated polymer poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV) in Tetrahydrofuran and 1, 2 Dichlorobenzene. We have prepared MEH-PPV using a modified procedure and purified several times in each step, the material offers low molecular weight, low polydispersity index an...

Self-consistent Polymer Reference Interaction Site Model ~PRISM! calculations and molecular dynamics ~MD! simulations were performed on athermal solutions of linear polymers. Unlike most previous treatments of polymer solutions, we explicitly included the solvent molecules. The polymers were modeled as tangent site chains and the solvent molecules were taken to be spherical sites having the sam...

In the past, investigations of phase separation in concentrated polymer solutions centered first of all on the crystallization kinetics (1) and morphology (2) of polymer crystals growing from solutions and, secondly, on the equilibrium thermodynamic properties of liquid-liquid phase separation phenomena (3). Papkov and Yefimova (4) have recently given a classification of different types of phas...

We investigate theoretically and numerically the effect of polymer additives on two-dimensional turbulence by means of a viscoelastic model. We provide compelling evidence that, at vanishingly small concentrations, such that the polymers are passively transported, the probability distribution of polymer elongation has a power law tail: Its slope is related to the statistics of finite-time Lyapu...

The morphology of solution-cast, phase-separated polymers becomes finer with increasing solvent evaporation rate. We address this observation theoretically for a model polymer where demixing is induced by steady solvent evaporation. In contrast to what is the case for a classical, thermal quench involving immiscible blends, the spinodal instability initially develops slowly and the associated l...

The dynamics of star polymers is investigated via extensive molecular and Brownian dynamics simulations for a large range of functionality f and packing fraction eta. The calculated isodiffusivity curves display both minima and maxima as a function of eta and minima as a function of f. Simulation results are compared with theoretical predictions based on different approximations for the structu...

2014 Some properties of semi-dilute poor and good solvent polymer solutions are examined within the framework of the field-theoretic formulism. The uncontrollable polydispersivity inherent in the field-theoretic formulism is shown to produce no errors if the quantity under investigation is molecular weight independent. A renormalization group cross-over calculation correct to order 03B5 is perf...

Submitted for the MAR10 Meeting of The American Physical Society Phase equilibria in polymer-blend thin films NIGEL CLARKE, MIREILLE SOUCHE, Durham University — To describe equilibrium concentration profiles in thin films of polymer mixtures, we propose a Hamiltonian formulation of the Flory-Huggins-de Gennes theory describing a polymer blend thin film. We first focus on the case of 50:50 polym...