模板诱导有机发光小分子定位沉积

通过模板诱导有机发光小分子定位沉积的方法构筑了大面积纳微米尺度的荧光图案.模板是以纳米压印技术构筑的聚合物微结构为阻挡层蒸镀金属,经Lift-off后形成的金属微结构.在模板表面,有机发光小分子与金属区域的结合能大于与裸硅片区域的结合能,因此,选择结构合适的模板可诱导有机发光小分子定位沉积.这种快速制备大面积荧光图案的...     

Pitch reduction lithography by pressure-assisted selective wetting and thermal reflow

We report on a new pitch reduction lithographic technique by utilizing pressure-assisted selective wetting and thermal reflow. The primary line-and-space pattern of low molecular weight polystyrene (PS) (Mw=17,300) was formed by solvent-assisted capillary force lithography (CFL), on which a diluted photoresist (PR) solution was selectively filled into the spaces by the application of a slight pressure (200 g cm(-2)). Subsequent removal of the PS pattern by toluene and ashing process led to a line pattern with approximately 50% pitch reduction. It was observed that the size reduction and space to width ratios were controllable by changing PR concentration and ashing time.     

Pattern formation in PMMA film induced by electric field

Micro‐sized patterns were created on thin poly(methyl methacrylate) (PMMA) films by the effect of external field, perpendicular to the film surface. The PMMA film, prepared by spin‐coating onto Si wafer, was heated to the fluid temperature (275 °C) and a linear pattern was created by the effect of electric field produced by a strip electrode. In another experiment, a round pattern was created as a result of local laser heating of the PMMA film under homogenous electrical field. The created patterns were analyzed by optical microscopy and profile meter. The dependence of the form and size of the created patterns on the intensity of the electric field, exposure time, and initial film thickness was examined. Wave guiding property of a linear pattern, produced by the above technique, was examined in a simple experiment. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1131–1135, 2009     

Fabrication of fluorescent surface relief patterns using AIE polymer through a soft lithographic approach

A new aggregation‐induced emission (AIE) active polymer (PS‐TPE) with high tetraphenylethene (TPE) loading density was synthesized. The synthesized polymer showed significant AIE properties, good solubility and high thermal stability. Soft‐lithographic contact printing process by using photoinduced surface relief structures on azo polymer film as masters and duplicated PDMS elastomer as stamps was used to fabricate fluorescent PS‐TPE patterns. Various fluorescent structures with high contrast including surface relief gratings, periodically dotted patterns, and quasi‐crystal structures can be easily fabricated through this approach. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1838–1845     

Properties of fracture surfaces of glassy polymers: Chain scission versus chain pullout

Fresh fracture surfaces formed by tensile failure of craze in molded polystyrene (PS) bars have been compared with the molded surfaces of the same bars, using an atomic force microscope with a thermal probe and operated in local thermal analysis. The results indicate that molecular weight is much higher in the interior of the sample than at the surface. No evidence was found for degradation of the PS chains via chain scission during crazing. Alternative explanations for the low‐molecular weights at the molded surface are discussed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

The mechanism of ultrasonic improvement of weld line strength of injection molded polystyrene and polystyrene/polyethylene blend parts

The effect of ultrasonic oscillations and ultrasonic oscillation‐induced modes on weld line strength of polystyrene(PS) and polystyrene/polyethylene(PS/HDPE) blend was investigated. And the mechanism of ultrasonic improvement of weld line strength of PS and PS/HDPE blend was also studied. The presence of ultrasonic oscillations can enhance the weld line strength of PS and PS/HDPE blend. Compared with mode I(ultrasonic oscillations were induced into mold at the whole process of injection molding), the induced ultrasonic oscillations as mode II(ultrasonic oscillations were induced into mold after injection mold filling) is more effective to increase weld line strength of PS and PS/HDPE blend. The mechanism for ultrasonic improvement of weld line strength of PS and PS/HDPE blend is that the ultrasonic oscillations can improve the molecular diffusion across weld line of the melt at the core, and make against the fusion of melt at the skin. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1520–1530, 2006     

Interface segregating fluoralkyl-modified polymers for high-fidelity block copolymer nanoimprint lithography

Block copolymer (BCP) lithography is a powerful technique to write periodic arrays of nanoscale features into substrates at exceptionally high densities. In order to place these features at will on substrates, nanoimprint offers a deceptively clear path toward high throughput production: nanoimprint molds are reusable, promote graphoepitaxial alignment of BCP microdomains within their topography, and are efficiently aligned with respect to the substrate using interferometry. Unfortunately, when thin films of BCPs are subjected to thermal nanoimprint, there is an overwhelming degree of adhesion at the mold-polymer interface, which compromises the entire process. Here we report the synthesis of additives to mitigate adhesion based on either PS or PDMS with short, interface-active fluoroalkyl chains. When blended with PS-b-PDMS BCPs and subjected to a thermal nanoimprint, fluoroalkyl-modified PS in particular is observed to substantially reduce film adhesion to the mold, resulting in a nearly defect-free nanoimprint. Subsequent lithographic procedures revealed excellent graphoepitaxial alignment of sub-10 nm BCP microdomains, a critical step toward lower-cost, high-throughput nanofabrication.     

Analysis of polystyrene surface properties on thin film bonding under carbon dioxide pressure using nanoparticle embedding technique

A gold nanoparticle embedding technique is used to determine how vacuum and pressured carbon dioxide (CO₂) affect polystyrene (PS) thin film properties. The pressured CO₂ greatly increased the gold nanoparticle embedding depth, possibly due to a low cohesive energy density near the film surface. For the monodisperse PS used in this study (M_n = 214,000), two spin‐coated thin films with intimate contact can be bonded below the bulk glass transition temperature (T_g) under CO₂ pressure when the embedded depth is larger than half of the gyration radius of PS molecules. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1535–1542, 2009     

Monolithic Silica Columns for HPLC,Micro‐HPLC,and CEC

Two types of monolithic silica columns derivatized to form an ODS phase, one prepared in a fused silica capillary (SR‐FS) and the other prepared in a mold and clad with an engineering plastic (poly‐ether‐ether‐ketone) (SR‐PEEK), were evaluated. The column efficiency and pressure drop were compared with those of a column packed with 5‐μm ODS‐silica particles and of an ODS‐silica monolith prepared in a mold and wrapped with PTFE tubing (SR‐PTFE). SR‐FS gave a lower pressure drop than a column packed with 5‐μm particles by a factor of 20, and a plate height of 20 μm at a linear velocity below 1 mm/s. SR‐PEEK showed higher flow‐resistance than the other monolithic silica columns, but they still showed a minimum plate height of 8–10 μm and a lower pressure drop than popular commercial columns packed with 5‐μm particles. The evaluation of SR‐FS columns in a CEC mode showed much higher efficiency than in a pressure‐driven mode.     

A facile route to regular and nonregular dot arrays by integrating nanoimprint lithography with sphere‐forming block copolymer directed self‐assembly

Nanoimprint lithography is used to create large‐area two‐dimensional prepatterns with tunable topographic heights in a resist layer. The resist prepatterns are applied to direct the self‐assembly of sphere‐forming polystyrene‐block‐polydimethylsiloxane block copolymers so as to form sparse nonregular nanodot arrays with flexible pattern layouts from high‐topography prepattern or dense regular nanodot arrays with a multiplicative pattern density from low‐topography prepattern. By precisely controlling the topographic height in substrate prepatterns, the origin of directed self‐assembly of block copolymer spheres using low‐topography prepattern is found to be topographic contrast. High‐fidelity pattern transfer from spherical block copolymer nanotemplates to functional materials indicates a promising route to ultrahigh density nanodevices. Bit‐patterned media over 1 teradot/in on a 2.5‐inch disk are fabricated, thus presenting future magnetic data storage media with great areal density growth potential. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 361–367     

Breaking embedded electrospun fibers (BEEF): Fabrication of polymer spheres encapsulated in polymer films

In this work, a novel method to fabricate polymer spheres encapsulated in polymer films by breaking embedded electrospun fibers (BEEF) was developed. Polymer fibers were first prepared by electrospinning and embedded in other polymer films using a three‐layer deposition method. After thermal annealing, the electrospun fibers transform into individual spheres with regular spacing and sizes. Poly(methyl methacrylate) (PMMA) and polystyrene (PS) are both used as the fiber or film materials. The transformation process can be observed in‐situ by optical microscope (OM) and is similar to the Plateau–Rayleigh instability. The growth rates of the surface undulation of the fibers are calculated, and higher growth rates are observed at higher annealing temperatures. The sizes of the encapsulated polymer spheres agree well with the theoretical predictions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2463–2470     

Influence of the efficacy of interfacial modification on the coarsening of cocontinuous PS/HDPE blends during quiescent annealing

This article studies the quiescent annealing of three different cocontinuous polystyrene/high‐density polyethylene blends modified with two types of interfacial agents of widely different efficacies. Quantitative analysis of phase growth was obtained using mercury porosimetry. In a previous work, it was shown that one of these modifiers, a symmetrical diblock copolymer, has a high affinity for the interface and demonstrates virtually no micelle formation prior to saturation of the blend interface. The other modifier, a hydrogenated SEBS of 70/30 composition, forms micelles at elevated concentrations of modifier. In this study, it is shown that the cocontinuous phase size grows linearly without modifier, whereas the addition of both interfacial modifiers significantly suppresses the PE/PS phase coarsening and results in nonlinear phase growth behavior. The effect of the diblock copolymer on suppressing coarsening, however, is much more effective than that for the triblock case clearly supporting the tendency toward micelle formation for that latter modifier. In the case of unmodified PE/PS, the driving force for capillary pressure effects is so high that it is the capillary instability phenomena that dominate the coarsening and hence result in a linear growth of pore size with annealing time. When interfacial modifiers are added, the influence of reduced interfacial tension and lower pore size polydispersity significantly diminishes both capillary pressure effects and capillary instability phenomena. In that case, capillary pressure becomes the main rate determining step resulting in a nonlinear dependence of pore size with annealing time. It is shown that both the viscosity of the phases and the temperature of annealing can strongly influence coarsening behavior at low levels of interfacial modifier. Under all those conditions, however, nonlinear phase growth for the partially compatibilized system was maintained. These results clearly show that careful quantitative coarsening experiments using mercury porosimetry can be used as a tool to analyze the efficacy of interfacial modifiers for highly continuous or cocontinuous systems. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 711–721, 2006     

Swelling of a polymer brush by a poor solvent

The addition of a small amount of a poor solvent impurity (methanol) to a theta solvent (cyclohexane) is found to cause appreciable swelling (≈30% increase of the average brush height) in a model end‐grafted polystyrene (PS) brush layer. This unusual type of swelling is not observed if octadecyltrichlorosilane (OTS) is first grafted to the portion of the silicon substrate uncovered by the grafting end‐groups of the PS chains. Brush swelling in the absence of OTS surface protection is interpreted as arising from a segregation of methanol to the solid substrate and the resulting modification of the polymer–surface interaction. We also observe that the addition of a small amount of methanol to an adsorbed PS layer exposed to cyclohexane causes rapid film delamination from the silicon substrate. Together these observations imply a strong influence of surface active impurities on the structure and adhesive stability of polymer layers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4126–4131, 2004     

Formation of parallel strips in thin films of polystyrene/poly(vinyl pyrrolidone) blends via spin coating on unpatterned substrates

Patterns of parallel strips, consisting of alternating polystyrene (PS) and poly(vinyl pyrrolidone) (PVP) regions, were observed in thin films spin cast from a PS/PVP/chloroform solution on unpatterned substrates. The formation of anisotropic patterns, manifested not only in thickness variation but also in composition variation, was found to be driven by Marangoni instability, with the PS and PVP streams flowing toward the preferred regions as the phase separation induced by solvent evaporation proceeded. The initial viscosity of the polymer solution and the thickness of the spin-cast films were lumped into one single parameter to study the phase morphology development at various initial polymer solution concentrations. Interestingly, the ratio of the square of the film thickness to the viscosity, a parameter loosely related to the Marangoni number, was found to reach a maximum value at the concentration where the strip patterns were most well-developed.     

Dewetting of a sol-gel-derived thin film

We report on the dewetting of a thin film produced by the sol-gel method. In the early stages of dynamic morphological instability, the drying stress in the capillary wave model determines the linearly scaling behaviors of the characteristic wavelength with the initial film thickness and the square law dependence of the number density of the dewetted holes on the film thickness. These power law dependences are weaker than those observed in the case of the spinodal dewetting of a polymer thin film. The wavelength determined in the early stages also dominates the scaling behaviors of the average length of the sides and number density of the polygons and the diameter of the droplets of the dewetting pattern with the film thickness in the final stages of the dynamic instability. We also observed that further drying eventually induces wrinkles in the droplets, rim, and film, which have a characteristic wavelength that can be theoretically predicted.     

Protrusion and deformation of an elastic particle at an advancing front interface

The response of an elastic particle to an extensional field close to an advancing liquid–gas interface in a capillary was examined both from an experimental and theoretical viewpoint. Experimental evidence is given on both the protrusion and deformation of an elastic particle at an advancing front interface. To interpret our experimental results, we followed and extended Hoffman's approach to the case of deformable particles. A hybrid approach was followed where the height of the bump was calculated theoretically as an equilibrium between capillary and drag forces for a given deformation of the particle, whereas the latter was supplied by an independent experimental measurement. For an elastic particle, the height of the bump goes through a maximum and further on decay almost linearly when plotted against the dimensionless parameter introduced by Hoffman. The difference between the theoretical prediction and the experimental data is discussed in relation to the asymmetry of the bump profiles observed in the experiment that could be responsible for a larger contribution of capillary forces from those calculated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1362–1374, 2003     

Materials for the preparation of polymer pen lithography tip arrays and a comparison of their printing properties

Polymer Pen Lithography (PPL) uses an array of polymeric tips, typically composed of poly(dimethyl siloxane), to transfer ink onto a surface and create patterns of soft molecules with micrometer to nanometer feature dimensions. In this study, tip arrays were fabricated from poly(methyl methacrylate), poly([methyl methacrylate]‐co‐[butyl methacrylate]), and poly(3‐mercaptopropylmethylsiloxane), and used to pattern 1‐mercaptohexadecanoic acid onto Au surfaces to determine the fidelity of pattern transfer by PPL as a function of the mechanical properties of the materials. It was found that the dependence between the applied force and feature edge length correlates directly to the mechanical properties of each of the polymers used to fabricate the tip arrays, where stiffer polymers have a reduced dependence between the applied force and feature size. This study demonstrates that PPL tip arrays can be composed of a wide variety of materials whose choice is determined by the desired printing application. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Novel amphiphilic block copolymers derived from the selective fluorination and sulfonation of poly(styrene‐block‐1,3‐cyclohexadiene)

Diblock copolymers of polystyrene‐block‐(1,3‐cyclohexadiene) (PS‐b‐PCHD), with varied molecular weights and compositions, were synthesized by sequential polymerization of styrene and 1,3‐cyclohexadiene (CHD) initiated by sec‐butyllithium in cyclohexane in the presence of appropriate additives during formation of the PCHD block. The residual double bonds in the PCHD block were saturated by addition of in situ generated difluorocarbene and/or hydrogen to enhance thermal and chemical stability. The fluorinated and/or hydrogenated polydiene blocks were chemically stable, allowing for controlled sulfonation of the PS blocks using acetyl sulfate. ¹H NMR and FT‐IR characterization confirmed successful fluorination/hydrogenation and sulfonation of the respective blocks. The resulting amphiphilic block copolymers consist of a semiflexible fluorine‐containing hydrophobic block having a bridged double ring structure and a hydrophilic sulfonated PS block. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Microfluidic chip fabrication using hot embossing and thermal bonding of COP

The application of silicon mold inserts by micro‐hot embossing molding has been explored in microfluidic chip fabrication. For the mold insert, this study employed an SU‐8 photoresist to coat the silicon wafer. Ultraviolet light was then used to expose the pattern on the SU‐8 photoresist surface. This study replicates the microstructure of the silicon mold insert by micro‐hot embossing molding. Different processing parameters (embossing temperature, embossing pressure, embossing time, and de‐molding temperature) for the cycle‐olefin polymer (COP) film of microfluidic chips are evaluated. The results showed that the most important parameter for replication of molded microfluidic chip is embossing temperature. De‐molding temperature is the most important parameter for surface roughness of the molded microfluidic chip. The microchannel is bonded with a cover by thermal bonding processing to form the sealed microfluidic chip. The bonding temperature is the most important factor in the bonding strength of the sealed microfluidic chip. Copyright © 2009 John Wiley & Sons, Ltd.     

Viscous flow of a volatile liquid on an inclined heated surface

We investigate the effects of evaporation on a gravity-driven flow of a viscous liquid on a heated solid surface. Vapor molecules are adsorbed on the dry areas of the solid and form a microscopic adsorbed film. The thickness of this film is calculated from the formulas for disjoining pressure and the principles of equilibrium thermodynamics. A lubrication-type approach is used to derive an evolution equation capable of describing both the macroscopic shape of the vapor-liquid interface and the adsorbed film on the vapor-solid interface. Under the conditions of negligible evaporation, the numerical solution of the evolution equation predicts translational motion and formation of capillary ridge, in agreement with previous investigations. Moderate evaporation is shown to slow down the flow and decrease the height of the capillary ridge, which implies a stabilizing effect of evaporation on the well-known instability observed in gravity-driven thin film flows. We also study the combined effects of evaporation and thermocapillary stresses and show that the latter act to reduce the velocity of the downward motion, but increase the height of the capillary ridge. Apparent contact angles are found from the solution and shown to increase with evaporation and contact line speed. For strong evaporation, steady state solutions are found such that evaporation balances the downward motion of the interface under the action of gravity.