Membranes with uniform, straight nanopores have important applications in diverse fields, but their application is limited by the lack of efficient producing methods with high controllability. In this work, we reported on an extremely simple and efficient strategy to produce such well-defined membranes. We demonstrated that neutral solvents were capable of annealing amphiphilic block copolymer (BCP) films of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) with thicknesses up to 600 nm to the perpendicular orientation within 1 min. Annealing in neutral solvents was also effective to the perpendicular alignment of block copolymers with very high molecular weights, e.g., 362 000 Da. Remarkably, simply by immersing the annealed BCP films in hot ethanol followed by drying in air, the originally dense BCP films were nondestructively converted into porous membranes containing highly ordered, straight nanopores traversing the entire thickness of the membrane (up to 1.1 μm). Grazing incident small-angle X-ray spectroscopy confirmed the hexagonal ordering of the nanopores over large areas. We found that the overflow of P2VP chains from their reservoir P2VP cylinders and the deformation of the PS matrix in the swelling process contributed to the transformation of the solid P2VP cylinders to empty straight pores. The pore diameters can be tuned by either changing the swelling temperatures or depositing thin layers of metal oxides on the preformed membranes via atomic layer deposition with a subnanometer accuracy. To demonstrate the application of the obtained porous membranes, we used them as templates and produced centimeter-scale arrays of aligned nanotubes of metal oxides with finely tunable wall thicknesses.

A SiO2 capping layer appears to have two advantages – increased areal yields and an improved morphological fidelity.

, P(S-b-2VP), micelles of nanometer size and core−shell spherical shape were deposited as monolayers on silicon substrates (SiO x /Si) with varied surface coverage using spin coating from polymer solutions in o-xylene of varied polymer concentration. Simply on varying the polymer solution, the micellar surface coverage on SiO x /Si, spatial order, and organization of micelles were tailored in the monolayer regime. The surface morphology of P(S-b-2VP) micelles was explored with grazing-incidence small-angle X-ray scattering (GISAXS) and an atomic force microscope (AFM). Quantitative analysis and simulations of the X-ray scattering pattern were performed to derive the dependence of the structural and ordering parameters of micelles on the P(S-b-2VP) concentration. Four spatial arrangements were investigated. Upon progressively increased surface coverage with increasing concentration, disordered spherical micelles, loosely packed spherical micelles with hexagonal order, ordered spherical micelles with random loosely packed densities, and closely packed spherical micelles with short-range order were obtained sequentially. This system thus serves as a model for analysis of the impact of surface coverage as a function of polymer concentration on the shape, size, size distribution, and assembly of truncated micelles within two-dimensional monolayers on SiO x /Si.

We investigated the response of symmetric poly(styrene-block-4vinylpyridine) P(S-b-4VP) diblock copolymer micelles to surface fields of variable strength at free surfaces and substrate interfaces when the micelles as spun were subjected to solvent annealing. Free surface interactions were controlled with solvent annealing in solvents of varied selectivity. On exposure to vapors of a solvent strongly selective for PS, the micelles retained their spherical shape but grew into cylindrical micelles or lamellar nanostructures via fusion on exposure to slightly selective or neutral solvent vapors. Giant 2D disks that completely wetted PS-grafted substrates resulted when spherical micelles were exposed to vapors of a highly selective solvent for P4VP. The interfacial interactions were controlled through subjecting them to UV/ozone (UVO) substrates initially coated with an end-grafted layer of short PS chains, with which the grafted PS chains became oxidized, degraded, or totally removed through UVO treatment for a controlled duration. When thin films were annealed in vapors of THF, the structural transition from spherical to cylindrical micelles depended on the interfacial field. On applying selective UVO exposure of optimal duration, we fabricated a substrate with two interfacial chemistries that promoted varied micellar species (spherical and cylindrical micelles) with a sharp boundary developed within thin films through solvent annealing for a controlled duration.

We demonstrate a simple, rapid, cost-effective and robust approach to modify the surface of a solid substrate, based on a UV-irradiated film of a general plastic polymer. Thin films of homopolymer polystyrene (PS) of controlled thickness were spin-coated on diverse metal, semiconductor and polymeric surfaces. Specific surface chemistry was tuned with UV irradiation in air (UVIA); interactions at the PS/substrate interface were enhanced with UV irradiation in nitrogen (UVIN). Oxidized and cross-linked PS served as a neutral surface on various metal, quartz, semiconductor and polymeric substrates to induce perpendicularly oriented cylinders or lamellae in a self-assembled block copolymer.

X-ray scattering in a grazing-incidence geometry (GISAXS) was used to study relief microstructures in thin films of asymmetric polystyrene-block-poly(methyl methacrylate) P(S-b-MMA) that dewetted on SiO x /Si and PMMA-SiO x /Si after isothermal annealing at 210°C for 12 h. The micro-and nanostructures of a P(S-b-MMA) film deposited on PS-SiO x /Si were studied for comparison. The diffuse scattering streaks observed at angles with respect to the film normal direction in the GISAXS patterns correlate with the formation of relief terraces comprising parallel PMMA cylinders packed within a PS matrix. The relief terraces reveal a facet-like wedge at the edge, resulting from partial wetting of the nonanchored P(S-b-MMA) top layer at contact angles in the range 4-6.5°on a monolayer of autophobic P(S-b-MMA) brushes anchored onto SiO x /Si and PMMA-SiO x /Si.

We investigated the structural evolution of truncated micelles in ultrathin films of polystyrene-block-poly(2-vinylpyridine), PS-b-P2VP, of monolayer thickness on bare silicon substrates (SiOx/Si) upon UV irradiation in air- (UVIA) and nitrogen-rich (UVIN) environments. The structural evolution of micelles upon UV irradiation was monitored using GISAXS measurements in situ, while the surface morphology was probed using atomic force microscopy ex situ and the chemical composition using X-ray photoelectron spectroscopy (XPS). This work provides clear evidence for the interpretation of the relationship between the structural evolution and photochemical reactions in PS-b-P2VP truncated micelles upon UVIA and UVIN. Under UVIA treatment, photolysis and cross-linking reactions coexisted within the micelles; photolysis occurred mainly at the top of the micelles, whereas cross-linking occurred preferentially at the bottom. The shape and size of UVIA-treated truncated micelles were controlled predominantly by oxidative photolysis reactions, which depended on the concentration gradient of free radicals and oxygen along the micelle height. Because of an interplay between photolysis and photo-crosslinking, the scattering length densities (SLD) of PS and P2VP remained constant. In contrast, UVIN treatments enhanced the contrast in SLD between the PS shell and the P2VP core as cross-linking dominated over photolysis in the presence of nitrogen. The enhancement of the SLD contrast was due to the various degrees of cross-linking under UVIN for the PS and P2VP blocks.

Small metal NPs at NEMCF exhibit a four-electron transfer pathway, a large kinetic current density and a small onset potential.