PS Template Research Articles

Double and Single Network Phases in Polystyrene-block-poly(l-lactide) Diblock Copolymers

Here, the phase behaviors of polystyrene-block-poly(l-lactide) (PS–PLLA) diblock copolymers are studied, and network phases can be found. In addition to conventional double gyroid phase with double networks, a single network phase (an Fddd phase with orthorhombic network) can be found, as evidenced by small-angle X-ray scattering and transmission electron microscopy (TEM). The single network texture with trivalent connectors of the Fddd can be directly visualized by using 3D TEM (i.e., electron tomography), and the observation under polarized light microscopy shows its birefringence character. The formation of stable Fddd is attributed to intrinsic inhomogeneity in the chain conformations of the chiral block (i.e., PLLA). Subsequently, nanoporous PS with continuous nanochannel networks can be obtained by hydrolysis of the PLLA block in the PS–PLLA and then used as a template for sol–gel reaction of tetraethyl orthosilicate. Consequently, nanoporous SiO2 with free-standing, well-defined network texture can be fabricated after removal of the PS template to give an open-cell porous ceramic material with high specific surface area (as high as 1170 m2/g) due to its nanostructured texture and high porosity.

Fabrication of ordered Au nanoparticles array and its optical absorption properties

Three kinds of polystyrene spheres with different sizes were fabricated on glasses by drifting method of nanosphere lithography. Au thin films with various thicknesses were prepared by magnetron sputtering under controlled deposition time. Triangle-shaped Au nanoparticles array in three different heights after removing the PS template were observed using scanning electron microscopy. The absorption characteristics of all samples were measured by ultraviolet-visible spectrophotometer. Surface plasmon resonance peak was seen to shift to the longer wavelength with increasing diameter of Au nanoparticles. And the surface plasmon resonance peak was shifted to the shorter wavelength with increasing height of Au nanoparticles. Based on Mie theory, we simulated the extinction properties, which vary with the diameter of Au nanoparticles, using Matlab software. The conclusion is in accordance with our experimental results.

Bicontinuous Ceramics with High Surface Area from Block Copolymer Templates

Mesoporous polymers with gyroid nanochannels can be fabricated from the self-assembly of degradable block copolymer, polystyrene-b-poly(L-lactide) (PS-PLLA), followed by hydrolysis of PLLA block. Well-defined polymer/ceramic nanohybrid materials with inorganic gyroid nanostructures in a PS matrix can be obtained by using the mesoporous PS as a template for sol-gel reaction. Titanium tetraisopropoxide (TTIP) is used as a precursor to give a model system for the fabrication of metal oxide nanostructures from reactive transition metal alkoxides. By controlling the rates of capillary-driven pore filling and sol-gel reaction, the templated synthesis can be well-developed. Also, by taking advantage of calcination, bicontinuous TiO(2) with controlled crystalline phase (i.e., anatase phase) can be fabricated after removal of the PS template and crystallization of TiO(2) by calcination leading to high photocatalytic efficiency. This new approach provides an easy way to fabricate high-surface-area and high-porosity ceramics with self-supporting structure and controlled crystalline phase for practical applications. As a result, a platform technology to fabricate precisely controlled polymer/ceramic nanohybrids and mesoporous ceramic materials can be established.

Using Sol–Gel Replications to Assess the Porosity of Block-Copolymer Derived Thin Films

In this paper, we report the use of a sol–gel replication method to prepare high fidelity SiO2 replicas of porous thin films obtained from microphase separated block-copolymer systems as an easy, robust, and rapid way to investigate their inner morphology. The cylinder-forming poly(styrene)-b-poly(lactide) (PS-b-PLA) block copolymer, containing a sacrificial block (PLA), was used to produce porous thin films with thicknesses above one periodical distance and bearing various internal organizations and orientations of the cylinders. The porosity was first infiltrated by silica precursors using a chemical solution deposition process, before being exposed to a brief thermal treatment to provoke inorganic condensation and elimination of the PS template. SEM observations of the obtained replica gave three-dimensional view of the internal topology of the porosity, which were then compared to structural characterizations obtained directly by AFM, SEM, or GISAXS on the parent block-copolymer films. It is shown that the replication provides an ideal tool to characterize the topology of porous networks in supported polymer thin films. This method can be generalized to any type of porous polymer media, offering a unique mode of visualization of the internal topology with valuable details at the substrate interface.

Block Copolymer Self-assembly on Ethylene Glycol (EG) Self-assembled Monolayer (SAM) for Nanofabrication

ABSTRACTNanostructure templates fabrication from P(S-b-MMA) thin films requires precise control of interfacial energies to achieve perpendicular orientation of microdomains to the substrate surface and can be obtained by modifying the oxide layer on silicon with a covalently anchored hydroxyl-terminated random copolymer P(S-r-MMA) termed a “neutral brush”. This commonly employed method enables precise fine-tuning of interfacial energies, but involves a lengthy process, requires starting materials that are commercially available but expensive, and results in a relatively thick under layer that can interfere with subsequent surface processing. We report here the microphase separation behaviour of an asymmetric P(S-b-MMA) diblock copolymer on electronic substrates modified with ethylene glycol (EG) self-assembled monolayer (SAM) as alternative to standard random copolymer brush. The diblock copolymer films deposited on EG SAMs upon thermal annealing spontaneously generates features with sub-lithographic resolution and pitch with perpendicular orientation. Selective etching provides a rapid route for the generation of PS template structures as the PMMA domains are etched at a faster rate. These templates can subsequently be used as etch masks to generate nanoscale features. We use state of the art lithography to generate sub-μm features and within these generate nm sized copolymer templates. Graphoepitaxy method proved a successful approach for the alignment of the microphase separated structures. This method of EG SAM driven self-0assembly provides a simple, rapid, yet tuneable approach for surface neutralization and nanofabrication technique for creating high density nanoscale features for the nanoelectronic industry.

Formation of dual-responsive polystyrene/polyaniline microspheres with sea urchin-like and core-shell morphologies

In the present work, a simple and effective approach has been employed to fabricate the polystyrene/polyaniline (PS/PANI) composite microspheres with various morphologies. PS/PANI composite microspheres exhibiting different structures such as sea-urchin like, core-shell structure, have been synthesized by seeded emulsion polymerization with polystyrene microspheres as seeds. In particular, the sea urchin-like PS/PANI composite microspheres, with radial array nanofibers on the surface, have demonstrated the switchable wettability between superhydrophilicity (0°) and superhydrophobicity (152°) under the response of either electrical potential or pH. This intelligible approach can produce sea urchin-like PS/PANI composite microspheres in bulk. The growth mechanism of sea urchin-like PS/PANI composite microspheres has also been elucidated. Following the dissolution of the PS template, the sea urchin-like polyaniline (PANI) hollow microspheres are obtained.

Highly Ordered 3D-Macroporous Poly(Para-Phenylene) Films Made by Electropolymerization of Benzene in an Ionic Liquid

Abstract A simple and efficient method for the preparation of highly ordered 3-dimensional macroporous polyparaphenylene (3DOM-PPP) conducting polymer films is reported for the first time. The method involves the simple electropolymerization of benzene inside a polystyrene opal template at mild reaction conditions. The ionic liquid 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([HMIm]FAP) containing benzene as a precursor is used as the electrolyte. Polystyrene colloidal crystals with average sphere-diameters of 240, 370 and 600 nm on ITO-glass substrates were used as templates. The obtained PPP inverse opal structures showed strong blue, green, yellow and red colors due to light diffraction caused by the 3-D highly ordered macroporous structure. A complete filling of the PS template with PPP can be easily achieved at room temperature. The electrochemical process was investigated by cyclic voltammetry and the deposits were characterized by SEM and IR analysis.

Excellent mechanical properties of three-dimensionally ordered macroporous nickel photonic crystals

High quality three-dimensionally ordered macroporous (3DOM) nickel photonic crystals (PCs) are fabricated using the polystyrene template-assisted electrodeposition method on nickel alloy substrate. The Ni 2+ in solution will firstly arrive in the electrode (nickel alloy substrate) and occupy the interstices among the PS template spheres; when enlarge the deposition time to 5 min, 3DOM nickel PCs will be achieved. The 3DOM nickel PCs grow firmly on the substrate due to the similar bounds between the PCs and substrate. Excellent mechanical properties are observed in the 3DOM nickel PCs, which may promote the practical applications of PCs.

Helical Nanocomposites from Chiral Block Copolymer Templates

Three-dimensional hexagonally packed PLLA nanohelices in the PS matrix were formed in the self-assembly of PS-PLLA chiral block copolymer. After hydrolysis of the PLLA blocks, PS with hexagonally packed helical nanochannels can be fabricated and treated as the template for the following sol-gel process. Subsequently, silica precursor mixture was introduced into the PS template by a pore-filling process. Well-defined helical nanocomposites with SiO(2) inorganic nanohelices orderly dispersed in polymeric matrix can be successfully obtained after the sol-gel process. As a result, with the combination of the self-assembly of degradable block copolymers and sol-gel chemistry, we suggest a novel method for the preparation of the helical nanocomposites with ordered texture.

Fabrication of metal nano dot dry etching mask using block copolymer thin film

Dense and periodic arrays of Au, Cr, Ni and Al nano dots were fabricated on silicon substrate. To obtain nano size patterns, self-assembling resists were used to produce a layer of uniformly distributed parallel cylinders of PMMA in a PS matrix. The PMMA cylinders were degraded and removed by acetic acid rinsing, forming a PS mask to transfer the pattern. The patterned holes of PS template were approximately 20 nm wide, 40 nm deep, and 50 nm apart. About 100 Å-thick Au, 30 Å-thick Cr, Ni, and Al thin film was deposited by using e-beam evaporator. PS template was removed by lift-off process using N -formyldimethylamine (DMF). Arrays of metal nano dots were dry etched by using fluorine-based reactive ion etching (RIE). As a result, the nano template of PS was analyzed with field-emission scanning electron microscope (FESEM) and the sizes of Cr, Ni, Au and Al nano dots left on Si surface were measured by atomic force microscope (AFM). The sizes of metal nano dots were in the range of 17–22 nm.

Pattern transfer using poly(styrene-block-methyl methacrylate) copolymer films and reactive ion etching

Self-assembly block copolymers have drawn a lot of attention for its great potential on critical dimension (CD) control and line-edge roughness (LER) reduction, which become more and more crucial as the CD of transistors is only tens of nanometers nowadays. In this study, lamellar-forming poly(styrene-b-methyl methacrylate) copolymer which fabricates line patterns was chosen for its ability to provide higher aspect ratio and vertical sidewall profile in template stage, thus more suitable for the following etching process to substrate. A dry plasma etching process using pure oxygen and pure argon plasma as example chemical etching gas and physical etching gas, respectively, was studied. Etching selectivity and lateral etch rate, which are responsible for the final template height and CD loss, had been characterized on a capacitive reactive ion etching tool. The templates formed by the proposed process had high aspect ratios, excellent pattern fidelity, and low LER values. The PS lateral etch rate was small enough to provide a wide process window for retaining the CD of the pattern during the template forming process. Subsequent silicon etching using the PS template made by dry etching process yielded a steep and smooth sidewall profile.

Synthesis and characterization of spherical and hemispherical polyepoxide micrometer‐sized particles of narrow size distribution by a single‐step swelling of uniform polystyrene template microspheres with glycidyl methacrylate

AbstractPolystyrene template microspheres of narrow size distribution were prepared by dispersion polymerization of styrene in a mixture of ethanol and 2‐methoxy ethanol. Spherical and hemispherical polystyrene/poly(glycidyl methacrylate) microspheres of narrow size distribution were prepared by a single‐step swelling of the polystyrene template microspheres with the swelling solvent monomer glycidyl methacylate, followed by polymerization of the monomer within the swollen template microspheres at 73 °C. Uniform polystyrene/poly(glycidyl methacylate‐ethylene glycol dimethacrylate) polyepoxide composite microspheres were synthesized similarly, substituting glycidyl methacylate for glycidyl methacylate and ethylene glycol dimethacrylate. Uniform crosslinked poly(glycidyl methacylate‐ethylene glycol dimethacrylate) polyepoxide microspheres have been prepared by dissolution of the PS template polymer of the former composite microspheres. Particles with different properties, for example size, size distribution, shape, surface morphology, surface area, and so forth, were prepared by changing various parameters belonging to the swelling and/or polymerization steps, for example, volume of the swelling monomer/s and/or the swelling solvent dibutyl phthalate. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4612–4622, 2007

Preparation of Three-dimensionally Ordered Macroporous Oxides by Combining Templating Method with Sol–Gel Technique

Abstract Three-dimensionally ordered macroporous (3DOM) inorganic oxides, SiO2 and TiO2, have been synthesized by combining template-assisted colloidal method with sol–gel technique. Close-packed PS beads were first prepared as template by using gravitational sedimentation, followed by infiltration with corresponding sol precursors rather than corresponding alkoxides, and then templates were removed by calcination. The morphology and crystalloid structure of samples were investigated by SEM and XRD, respectively. The results indicate that the structures of samples are well-inverse replicas of PS template and the method is also applicable to the preparation of other oxides.

Fabrication of Ordered TiO2 Porous Thin Films by Sol-Dipping PS Template Method

Monolayer polystyrene spheres (∼400 nm) array templates were assembled orderly on clean glass substrates by dip-drawing method from emulsion of PS and porous TiO2 thin films were prepared by using sol-dipping template method to fill TiO2 sol into the interstices among the close-packed PS templates and then annealing to remove the PS templates. The effects of TiO2 precursor sol concentration and dipping time in sol on the porous structure of the thin films were studied. The results showed pore size of the ordered TiO2 porous thin film depended mainly on PS size and partly on TiO2 sol concentration. The shrinkage of pore diameter was about 10% for 0.2 M and 20% for 0.4 M TiO2 sol concentrations. X-ray diffraction (XRD) spectra indicated the porous thin film was anatase structure. The transmittance spectrum showed that optical transmittance of the porous thin film kept above 70% beyond the wavelength of 430 nm. Optical band-gap of the porous TiO2 thin film (fired at 550∘;C) was 3.12 eV.

Porous TiO2hollow spheres by liquid phase deposition on polystyrene latex-stabilised Pickering emulsions

Hollow TiO2-composite spheres in the size range of 50–150 µm were prepared by liquid phase deposition on template assemblies of self-organised PS latex particles. These assemblies spontaneously formed on the surface of octanol droplets in an oil-in-water emulsion, the overall process resembling the stages of natural biomineralisation. The TiO2–polymer composite capsules were converted into highly porous inorganic spheres by dissolution of the PS template particles and calcination at various temperatures. Removal of the organic template was monitored by DTA/TGA and He-pycnometry. The microstructure of the TiO2 films was characterised by nitrogen sorption and XRD measurements. The calcination temperature dependence of the photocatalytic activity of the hollow spheres was assessed by UV induced degradation of DCA. High photocatalytic activity was observed after calcination at 200 °C due to a high specific surface area of the film and the formation of micropores and mesopores in the size range <4 nm. Calcination at higher temperatures leads to the formation of larger mesopores and a drop in the photocatalytic activity due to a decrease in specific surface area and the disappearance of pores <4 nm. A major fraction of the deposited film consists of crystalline TiO2 in anatase modification. Further crystallisation and crystal growth at higher calcination temperatures has only minor influence on the photocatalytic activity.