Papers by Keyword: Diblock Copolymer

Abstract: The progress of information technology has increased the demand of the capacity of storage media. Bit patterned media (BPM) has been known as a promising method to achieve the magnetic-data-storage capability of more than 1 Tb/in.². In this work, we demonstrated fabrication of magnetic nanodot array of CoPt with a pitch of 33 nm using a pattern-transfer method of block copolymer (BCP) self-assembly. Carbon hard mask (CHM) was adopted as a mask to pattern-transfer self-assembled nanodot array formed from poly (styrene)-b-poly (dimethyl siloxane) (PS-PDMS) with a molecular weight of 30,000-7,500 mol/g. According to our experiment results, CHM showed its high selectivity against CoPt in Ar ion milling. Therefore, this result boosted the potential of BCP self-assembly technique to fabricate magnetic nanodot array for the next generation of hard disk drive (HDD) due to the ease of large-area fabrication, and low cost.

Abstract: We present molecular dynamic (MD) simulations to model and simulate the self-assembly of asymmetrical diblock copolymers (DCP) confined in carbon nanotube (CNT). The strength of the attractive interaction is systemically varied to examine effects on the self-assembled morphologies. The aim of our study is to understand how the surface energy and cohesive energy affect the structure. The dependence of the chain conformation on the strength of the surface preference is reasonably explained. The energetics is discussed qualitatively and used to account for the appearance of the complex morphological transition.

Abstract: The formation process of diblock copolymer brushes, formed by the adsorption of flexible chains on the surface is studied by Molecular Dynamic simulations. The surface adsorption density has been distinguished, depending on the various chain structures and counterions. The mode was considered as size ratio of A-block lengths to the the chain length, B-block carries the positive charge, and add counterions to the system. The result shows that the surface adsorption density is affected strongly by ratio of A-block length to the chain length, inhibited by the counterions, which is qualitatively consistent with experiments. These initial findings can be used as a guide for the preparation of actual diblock polymer brushes on metal crystal surfaces membranes by the adsorption approach.

Abstract: Ag/ZnO powders were synthesized through a precipitation method, using poly(ethylene oxide)-block-poly(propylene oxide) as stabilizer. X-ray diffraction patterns of all prepared powders showed a mixed phase of Ag and ZnO. The existence of metallic Ag on the surface of all prepared ZnO powders was confirmed by X-ray photoelectron spectroscopy. Their photocatalytic activities were investigated through the degradation of a methylene blue solution under blacklight illumination. The Ag/ZnO prepared from the Zn²⁺ solution containing 7 mol% of Ag⁺ had the highest photocatalytic activity and this also showed better photocatalytic activity than a commercial ZnO powder.

Abstract: We use molecular dynamics simulations method to investigate the behavior characteristics of AB diblock copolymers that are adsorbed on a planar surface. Adsorption density has been distinguished, depending on the adsorption manner of A-block on the (100) surface and formation of brushes. It is examined in detail that conformational behavior of the brushes affects the adsorption density. In addition, we make a comparison of linear brush with length ratio of the A-block to the chain, in the cases of the fixed length of chain and the fixed length of A-block, respectively. The result shows that the adsorption density is strongly affected by the length ratio of the A-block to the chain. And our findings can be used as a guide for fabrication and preparation of actual synthetic polymer brushes on a solid surface by the approach of physical adsorption.

Abstract: Structure transitions induced by selective solvents in diblock copolymer films are investigated by density functional theory. By changing the selectivity and the packing fraction of selective solvents, the disorder-lamellar transition, the position switched lamellar phase transitions and the reentrant transitions are observed. Phase diagrams are constructed to clarify these effects. The results provide an effective way to control the transitions between the different microstructures.

Abstract: Coarse-grained molecular dynamics simulations on self-assembly behavior of diblock copolymers (DCP) with nanoparticles confined in cylindrical nanopores are perfomed to study the morphology transition of DCP affected by the confined ratio of the cylindrical confinement diameter to the block copolymer domain spacing, the wall-polymer interactions, the particle-polymer interaction potential and the component concentration. The simulation results show that nanoparticles have a pronounced effect on the morphology transition of DCP and can therefore be considered as an important aspect in controlling the confined self-assembly in cylindrical confinement. Besides, the phase diagram indicates the process of morphology transition.

Abstract: The synthesis and characterization of well-dispersed Bi2O3 nanoclusters from diblock copolymer are reported. A diblock copolymer template of norbornene derivatives was synthesized using ring-opening metathesis polymerization. By introducing BiCl3 into the diblock copolymer template, the bismuth oxide nanoclusters within the copolymer micelles were achieved by NaOH soaking and water wash. Finally, FTIR and TEM were used to characterize the nanocomposite morphology and the process of oxide formation

Abstract: In this paper, a system polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) were synthesized by nitroxide-medium controllable free radical polymerization. PS-b-P4VP were characterized by 1H-nuclear magnetic resonance (1H-NMR), infrared spectrum (FTIR) and gel permeation chromatography (GPC). The results have indicated that diblock copolymers can be prepared and with molecular polydispersities in the range of 1.08 to 1.31. The structure of diblock was showed by 1H-nuclear magnetic resonance.

Abstract: a system of polystyrene and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) were synthesized by using living free radical in the presence of 4-hydroxyl-2, 2, 6, 6-tetramethylpiperridine-oxyl-1(HTEMPO•) and (BPO). The polystyrene and diblock copolymers were characterized by gel permeation chromatography (GPC) and atomic force microscope (AFM). The results suggested that the polymerization of styrene in the presence of 4-hydroxyl-2, 2, 6, 6-tetramethylpiperridine-oxyl-1(HTEMPO•) and benzoyl peroxide (BPO) can be prepared with molecular weight distribution in the range of 1.15 to 1.25. The polystyrene with living groups can continuously initiate the living free radical polymerization of 4-Vinylpyridine to form the polystyrene-block-poly (4-vinylpyridine) with molecular weight distribution in the range of 1.08 to 1.35. The AFM of diblock indicated the diblock copolymer（PS-b-P4VP） is a good compatibilizer for PS and P4VP.