Yong Lak Joo

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Coarse-grained, molecular dynamics (MD) simulations have been conducted to study the effect of shear flow on polymer nanocomposite systems. In particular, the interactions between different components have been tuned such that the nanoparticle-nanoparticle attraction is stronger than nanoparticle-polymer interaction, and therefore, the final equilibrium(More)
Mesoscale simulation, electrospinning and Raman scattering experiments have been carried out to demonstrate that examination and control of nanorod configuration in a polymer matrix under elongational flow and confinement can lead to enhanced sensing. First, coarse-grained molecular dynamics (CGMD) was employed to probe the diffusivity, orientation, and(More)
Multiaxial (triaxial/coaxial) electrospinning is utilized to fabricate block copolymer (poly(styrene-b-isoprene), PS-b-PI) nanofibers covered with a silica shell. The thermally stable silica shell allows post-fabrication annealing of the fibers to obtain equilibrium self-assembly. For the case of coaxial nanofibers, block copolymers with different isoprene(More)
Ghosh et al. ~2001! demonstrated that the Kramers chain captures the optical and rheological properties of dilute polymer solutions in rapidly varying elongational flows better than the finitely extensible nonlinear elastic dumbbell model. A new model, based on introducing an adaptive length scale ~ALS! as an internal variable, is developed to reproduce the(More)
Using Brownian dynamics simulations of wormlike chain bead-spring models, the dynamics of linear and star-branched polyelectrolyte molecules traveling through an array of entropic traps during electrophoresis have been investigated. First, the effectiveness of using coarse-grained bead-spring systems for linear molecules to model the electrophoretic process(More)
Silicon nanoparticles (Si NPs) wrapped by graphene in carbon nanofibers were obtained via electrospinning and subsequent thermal treatment. In this study, water-soluble poly(vinyl alcohol) (PVA) with low carbon yield is selected to make the process water-based and to achieve a high silicon yield in the composite. It was also found that increasing the amount(More)
Coaxial nanofibers with poly(styrene-block-isoprene) (PS-b-PI)/magnetite nanoparticles as core and silica as shell are fabricated using electrospinning.1-4 Thermally stable silica helps to anneal the fibers above the glass transition temperature of PS-b-PI and form ordered nanocomposite morphologies. Monodisperse magnetite nanoparticles (NPs; 4 nm) are(More)
Nanofibers are synthesized by electrospinning highly loaded water-based precursor-polymer hybrid solutions followed by thermal treatment to control crystal structure. Electrical conductivity and magnetic coercivity, as shown, are tested displaying independent magnetic and electrical property control from coercive to superparamagnetic and resistive to(More)
Monoaxial silica nanofibers containing iron species as well as coaxial nanofibers with a pure silica core and a silica shell containing high concentrations of iron nanocrystals were fabricated via electrospinning precursor solutions, followed by thermal treatment. Tetraethyl-orthosilicate (TEOS) and iron nitrate (Fe(NO(3))(3)) were used as the precursors(More)
We have investigated the effect of nanorods on the symmetry breaking of a model diblock copolymer under cylindrical confinement using coarse-grained molecular dynamics. Unlike nanoparticles, nanorods can readily be interconnected with each other and also induce connection across self-assembly domains at much lower loading than nanoparticles. Such(More)