The reaction mechanism of the redox initiation system persulfate/N,N,N',"-tetramethylethylenediamine (TMEDA) was studied by spin trapping technique and ESR spectra. The free radical (CH, hNCH,CH,(CH, )NCH; (1) is one of the initial free radicals responsible for the initiation of the vinyl polymerization in addition to the sulfate free radical (HqSO'). The result of amino end group analysis confirmed the fact that the free radical 1 initiates vinyl polymerization and becomes the end group of the resulting polymers. The effect of TMEDA concentration on the final percentage of conversion of acrylamide polymerization and on the molecular weights of the resulting polymer were also studied. An initiation mechanism was proposed.

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Using cell dynamics computer simulation, we perform a systematic study of thin block copolymer films around a nanoparticle. Lamellar-, cylinder-, and sphere-forming block copolymers are investigated with respect to different film thicknesses, particle radii, and boundary conditions at the film interfaces. The obtained structures include standing lamellae and cylinders, "onions", cylinder "knitting balls", "golf ball", layered spherical, "virus"-like and mixed morphologies with T-junctions and U-type defects. The kinetics of the structure formation and difference with planar thin films are discussed. Our simulations suggest that novel porous nanocontainers can be formed by the coating of a sacrificial nanobead by a block copolymer layer with a well-controlled nanostructure. In addition, first scanning force microscopy experiments on a model system reveal surface structures similar to those predicted by our simulations.

Direct numerical simulation is performed to study the effect of progressive gravity waves on turbulence underneath. The Navier-Stokes equations subject to fully nonlinear kinematic and dynamic free-surface boundary conditions are simulated on a surface-following mapped grid using a fractional-step scheme with a pseudo-spectral method in the horizontal directions and a finite-difference method in the vertical direction. To facilitate a mechanistic study that focuses on the fundamental physics of wave-turbulence interaction, the wave and turbulence fields are set up precisely in the simulation: a pressure-forcing method is used to generate and maintain the progressive wave being investigated and to suppress other wave components, and a random forcing method is used to produce statistically steady, homogeneous turbulence in the bulk flow beneath the surface wave. Cases with various moderate-to-large turbulenceto-wave time ratios and wave steepnesses are considered. Study of the turbulence velocity spectrum shows that the turbulence is dynamically forced by the surface wave. Mean flow and turbulence vorticity are studied in both the Eulerian and Lagrangian frames of the wave. In the Eulerian frame, statistics of the underlying turbulence field indicates that the magnitude of turbulence vorticity and the inclination angle of vortices are dependent on the wave phase. In the Lagrangian frame, wave properties and the accumulative effect on turbulence vorticity are studied. It is shown that vertical vortices are tilted in the wave propagation direction due to the cumulative effects of both the Stokes drift velocity and the correlation between turbulence fluctuations and wave strain rate, whereas for streamwise vortices, these two factors offset each other and result in a negligible tilting effect.