Characterization of Poly(2-vinylpyridine) by Temperature Gradient Interaction Chromatography

Characterization of Poly(2-vinylpyridine) by Temperature Gradient Interaction Chromatograph

Extremely Superhydrophobic Surfaces with Micro- and Nanostructures Fabricated by Copper Catalytic Etching

We demonstrate a simple method for the fabrication of rough silicon surfaces with micro- and nanostructures, which exhibited superhydrophobic behaviors. Hierarchically rough silicon surfaces were prepared by copper (Cu)-assisted chemical etching process where Cu nanoparticles having particle size of 10−30 nm were deposited on silicon surface, depending on the period of time of electroless Cu plating. Surface roughness was controlled by both the size of Cu nanoparticles and etching conditions. As-synthesized rough silicon surfaces showed water contact angles ranging from 93° to 149°. Moreover, the hierarchically rough silicon surfaces were chemically modified by spin-coating of a thin layer of Teflon precursor with low surface energy. And thus it exhibited nonsticky and enhanced hydrophobic properties with extremely high contact angle of nearly 180°

sj-pdf-1-smx-10.1177_00811750231183711 – Supplemental material for Choosing an Optimal Method for Causal Decomposition Analysis with Continuous Outcomes: A Review and Simulation Study

Supplemental material, sj-pdf-1-smx-10.1177_00811750231183711 for Choosing an Optimal Method for Causal Decomposition Analysis with Continuous Outcomes: A Review and Simulation Study by Soojin Park, Suyeon Kang and Chioun Lee in Sociological Methodology</p

Interaction-Controlled HPLC for Block Copolymer Analysis and Separation

An interaction-controlled HPLC technique has been developed to analyze homopolymer precursors in block copolymer systems that are not easily identified by size exclusion chromatography (SEC) and to obtain block copolymers that are homopolymer-free and compositionally narrower than the as-synthesized ones. We demonstrate that a “single peak” in SEC does not necessarily mean that the block copolymers are free of homopolymers (due to limitations in the SEC analysis of block copolymers) and propose to employ the interaction-controlled HPLC strategy for rigorous analysis and purification of block copolymers in terms of their chemical heterogeneity

Fabrication of Nanoporous Block Copolymer Thin Films through Mediation of Interfacial Interactions with UV Cross-Linked Polystyrene

Fabrication of Nanoporous Block Copolymer Thin Films through Mediation of Interfacial Interactions with UV Cross-Linked Polystyren

From Nanorings to Nanodots by Patterning with Block Copolymers

We demonstrate three different transfer patterns that can be achieved by use of a surface reconstructed block copolymer film where metal is evaporated onto the surface of the film, providing the contrast. Thin films of diblock copolymers having cylindrical microdomains oriented normal to the surface with long-range lateral order were used. Solvent reconstruction of the film, followed by a glancing angle metal evaporation and thermal annealing, led to three different decorations of the films with gold. These films were used as masks for pattern transfer of pores, columns, and rings to underlying substrate with high fidelity

Bio-oil Analysis Using Negative Electrospray Ionization: Comparative Study of High-Resolution Mass Spectrometers and Phenolic versus Sugaric Components

We have previously demonstrated that a petroleomic analysis could be performed for bio-oils and revealed the complex nature of bio-oils for the nonvolatile phenolic compounds (Smith, E.; Lee, Y. J. Energy Fuels 2010, 24, 5190−5198). As a subsequent study, we have adapted electrospray ionization in negative-ion mode to characterize a wide variety of bio-oil compounds. A comparative study of three common high-resolution mass spectrometers was performed to validate the methodology and to investigate the differences in mass discrimination and resolution. The mass spectrum is dominated by low mass compounds with <i>m</i>/<i>z</i> of 100–250, with some compounds being analyzable by gas chromatography–mass spectrometry (GC–MS). We could characterize over 800 chemical compositions, with only about 40 of them being previously known in GC–MS. This unveiled a much more complex nature of bio-oils than typically shown by GC–MS. The pyrolysis products of cellulose and hemicellulose, particularly polyhydroxy cyclic hydrocarbons (or what we call “sugaric” compounds), such as levoglucosan, could be effectively characterized with this approach. Phenolic compounds from lignin pyrolysis could be clearly distinguished in a contour map of double bond equivalent (DBE) versus the number of carbons from these sugaric compounds

Ordering of PS-<i>b</i>-P4VP on Patterned Silicon Surfaces

We demonstrate a method to fabricate high-quality patterned micelle arrays using poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) block copolymer. Long-range order of the PS-b-P4VP micelle in hexagonal arrays was induced by topographic grating patterns during solvent annealing. The size and row spacing of block copolymer micelle arrays created in this way were uniform. By controlling the thickness of the polymer on the crests and in the troughs of the grating patterns, we prepared PS-b-P4VP micelle arrays having different sizes

A Simple Route to Highly Oriented and Ordered Nanoporous Block Copolymer Templates

Controlling the orientation and lateral ordering of the block copolymer microdomains is essential to their use as templates and scaffolds for the fabrication of nanostructured materials. In addition, a process must be robust, simple to implement, and rapid, and should not introduce disruptive processing steps that would impede their use. Here, we describe thin films of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) diblock copolymers, spin-coated from mixed solvents that show highly oriented, cylindrical microdomains with a high degree of order on a wide range of substrates, including silicon oxide, polystyrene, germanium, polyimide, and poly(butylene terephthalate). In addition, the preferential solvation of the P4VP block with an alcohol caused a surface reconstruction that resulted in the formation of a nanoporous film upon drying. The evaporation of gold onto the reconstructed films produced thermally stable and reactive ion etching resistant films

Solvent-Induced Transition from Micelles in Solution to Cylindrical Microdomains in Diblock Copolymer Thin Films

It is well-known that block copolymer thin films can be easily prepared on different substrates by spin coating. Here, we show that the cylindrical microdomains of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) copolymers can be oriented normal to the surface over a large area by spin coating in toluene/THF solvent mixture. The structure and size of the PS-b-P4VP in solution were compared with those in thin films. It was found that the cylindrical microdomains, obtained by spin coating, oriented normal to the film surface depended strongly on the amount of THF in the casting solution. The study was extended to PS-b-P4VP copolymers with different molecular weights and compositions, which allowed the control of the size of the cylindrical domains and the areal density of the arrays