Won Bo Lee

We present a coarse-grained model in order to describe the unusual sequence of mesophases observed in aqueous solutions of nonionic lipids, such as monoolein. The lipid molecules are modeled as a rigid head and a flexible Gaussian tail, and water is treated explicitly. A key component of the model is thermally reversible hydrogen bonding between the lipid head and water resulting in changes in both head volume and the interactions of the hydrated head with its surroundings. Phase diagrams obtain

Thermoreversible, supramolecular self-assembly in multiblock copolymer melts is investigated with two microscopic approaches. We consider a blend consisting of two chemically distinct, but reactive homopolymers. One homopolymer has a single reactive end group at one of its ends, while the second has functional end groups at both ends. Reversible bonding is constrained to occur between dissimilar blocks so that this mixture is capable of forming diblocks and triblocks but no other copolymers. All

Stress autocorrelation functions (SAF) of entangled polymer melts are calculated by coarse-grained molecular dynamics (MD) simulations. We show that time-averaged stresses reduce the strong noise in SAFs while still capturing most relevant relaxations of the chains. Plateau values of the SAF compare well with plateau values predicted from the entanglement length evaluated via primitive path analysis (PPA) and from experiment (where available). Three types of polymer models are studied: a flexibl

The higher catalytic activity and stability for a gas-phase carbonylation of dimethyl ether (DME) to methyl acetate (MA) on the seed-derived ferrierite (FER) were attributed to its higher crystallinity with small amounts of defect sites by recrystallization methods without using any organic structure directing agent. The recrystallized FER (FER-S1) with its smaller amount of Lewis acidic extraframework Al sites (EFAl) possessed proper number of Brønsted acidic sites in the eight-membered-ring (8

Developing next-generation solid sorbents to improve the economy of pre- and post-combustion carbon capture processes has been challenging for many researchers. Magnesium oxide (MgO) is a promising sorbent because of its moderate sorption-desorption temperature and low heat of sorption. However, its low sorption capacity and thermal instability need to be improved. Various metal-promoted MgO sorbents have been experimentally developed to enhance the CO2 sorption capacities. Nevertheless, rigorou

Equilibrium phase morphologies of two different dendritic block copolymer melts are calculated and compared. These copolymers have a pitchfork-like architecture and consist of three distinct blocks that correspond roughly to the handle, the connecting middle dendron structure, and the attached tines of a pitchfork. The first melt considered consists of a copolymer that has a simple Y-junction middle block, and it connects the handle to two tines. The second is similar except its dendritic middle

In this study, a practical strategy to develop a microkinetic model for methanol synthesis from syngas over a Cu-based catalyst is described. The comprehensive model consists of forward and backward reactions of 28 possible elementary-step reactions for CO and CO2 hydrogenation and the water–gas shift reaction. A combination of ab initio density functional theory (DFT) and semiempirical unity bond index–quadratic exponential (UBI-QEP) methods was used to determine the heat of adsorption and acti

A model to describe the self-assembly properties of aqueous blends of nonionic lipids is developed in the framework of self-consistent field theory (SCFT). Thermally reversible hydrogen bonding between lipid heads and water turns out to be a key factor in describing the lyotropic and thermotropic phase behavior of such systems. Our model includes reversible hydrogen bonding imposed in the context of the grand canonical ensemble and exact conditions of binding equilibrium. The lipid molecules are

A complex coacervate is the polymer-rich phase resulting from liquid–liquid phase separation induced by two oppositely charged polyelectrolytes in an aqueous solution, which shows the considerable potential of functional materials and the substantial role of biological processes. In this study, the phase behavior of complex coacervates for differently charged moieties is investigated using well-defined polyether-based polyelectrolytes functionalized with ammonium, guanidinium, sulfonate, and car