(~175 words) The development of wrinkled polymer thin film structures is viewed optimistically fo... more (~175 words) The development of wrinkled polymer thin film structures is viewed optimistically for the potential development of next generation high-tech devices such as stretchable electronics, microlens arrays, and smart surfaces. Here for the first time, we report a fast, facile method of developing wrinkled patterns where the wrinkles are formed spontaneously, in one step, simply upon solvent casting an azlactone-based polymer onto a substrate, without the need to apply any external stress to the system. The directionality of these wrinkles can be easily tailored by changing the mode of deposition of the polymer films onto the substrates. This methodology is not only simple, but also versatile and robust and could easily be adapted for 3D surfaces and other nonplanar, complex geometries. The persistence of these wrinkles over large distances is apparent, as we have noticed a uniform, sinusoidal wrinkling pattern across the full length of a 12 ” wafer. We expect that this simple, straightforward strategy of wrinkle formation in thin films comprised of a reactive polymer offers myriad possibilities for creating spatially and chemically tailored interfaces for modern
Colloids and Surfaces a Physicochemical and Engineering Aspects, Feb 1, 2010
ABSTRACT The paper summarizes the results of a study on the basic properties (film thickness, con... more ABSTRACT The paper summarizes the results of a study on the basic properties (film thickness, contact angle film/meniscus and gas permeability) of foam films stabilized with the anionic perfluoro octane sulfonate (PFOS) surfactant. The surfactant was used as a tetraethyl ammonium salt. The dependencies on the electrolyte (NH4Cl) and surfactant concentration were studied. Strong dependence of the film thickness and the contact angle on the concentration of NH4Cl and PFOS was observed. Well pronounced transition in the film thickness from common black (electrostatically stabilized) films to Newton black (sterically stabilized) films was registered. The critical salt concentration necessary for the formation of NBF was defined to be 0.1M NH4Cl. The contact angles between the films and the meniscus were collected.The gas permeability coefficient (K, cm/s) was measured at various conditions. The permeability coefficient of NBF decreases with increasing surfactant concentration below the cmc and remains constant above it. The gas permeability of the films depends on the salt concentration, respectively the film thickness in a complicated manner which cannot be explained by simple application of the Fick's law of diffusion.
ABSTRACT Block copolymers with metals confined in one or more blocks are emerging as candidate ma... more ABSTRACT Block copolymers with metals confined in one or more blocks are emerging as candidate materials for nanomanufacturing applications due to their unprecedented nanoscale pattern transfer capabilities. In this article we highlight recent developments in metal-containing block copolymers in terms of their novel synthetic methodologies with particular emphasis on sequential infiltration synthesis, their hierarchical self-assembly from nano, meso, and submicron scales, and their applications as an etch mask for high-throughput, high-aspect-ratio nano and meso scale patterning.
Block copolymers (BCPs) consist of two or more chemically distinct and incompatible polymer chain... more Block copolymers (BCPs) consist of two or more chemically distinct and incompatible polymer chains (or blocks) covalently bonded. Due to the incompatibility and connectivity constraints between the two blocks, diblock copolymers spontaneously self-assemble into microphase-separated nanoscale domains that exhibit ordered 0, 1, 2 or 3 dimensional morphologies at equilibrium. Commonly observed microdomain morphologies in bulk samples are periodic arrangements of lamellae, cylinders, or spheres. Block copolymer lithography refers to the use of these ordered structures in the form of thin films as templates for patterning through selective etching or deposition. The self-assembly and domain orientation of block copolymers on a given substrate is critical to realize block copolymer lithography as a tool for large throughput nanolithography applications. In this work, we survey the morphology of cylinder-forming block copolymers by atomic force microscopy (AFM). Three kind of block copolym...
A series of tree-shaped, amphiphilic dendrimers was synthesized. The products belong to the famil... more A series of tree-shaped, amphiphilic dendrimers was synthesized. The products belong to the family of one-directional arborols of the form ([9]-n), where the notation signifies that each molecule has nine hydroxyl groups ([9]-) as the hydrophilic head and an alkyl chain as the hydrophobic moiety (n = 6, 8, or 10 carbon atoms). The surfactant character changes dramatically as the number of methylene groups increases. The critical micelle concentration of [9]-6 was determined, and pressure-area isotherms of the less soluble [9]-8 and [9]-10 were obtained. Large structures existed atop the spread layers. Large structures were also found in solutions of [9]-6.
ABSTRACT Charge-regulated synthesis of triangular prisms in aqueous solution using self-assembled... more ABSTRACT Charge-regulated synthesis of triangular prisms in aqueous solution using self-assembled polyelectrolyte micelles as templates is described in detail. Micelles formed from amphiphilic polystyrene-block-sulfonated poly(1,3-cyclohexadiene) (PS-b-sPCHD) serve as templates to direct the formation of novel triangular prisms of CuCl2 single crystals. We demonstrate that the edge lengths of these triangular prisms can be easily tailored at room temperature from the nanoscale to the mesoscale by simply adjusting the ratio of charged micelles to protons in the solution. This approach can be extended to the preparation of different ordered crystal structures with a precision hard to achieve via other approaches.
Palladium has been extensively studied as a material for hydrogen sensors because of the simplici... more Palladium has been extensively studied as a material for hydrogen sensors because of the simplicity of its reversible resistance change when exposed to hydrogen gas. Various palladium films and nanostructures have been used, and different responses have been observed with these diverse morphologies. In some cases, such as with nanowires, the resistance will decrease, whereas in others, such as with thick films, the resistance will increase. Each of these mechanisms has been explored for several palladium structures, but the crossover between them has not been systematically investigated. Here we report on a study aimed at deciphering the nanostructure-property relationships of ultrathin palladium films used as hydrogen gas sensors. The crossover in these films is observed at a thickness of approximately 5 nm. Ramifications for future sensor developments are discussed.
Poly(styrene-block-ferrocenyldimethylsilane) (PS-b-PFS) is a metal-containing block copolymer tha... more Poly(styrene-block-ferrocenyldimethylsilane) (PS-b-PFS) is a metal-containing block copolymer that exhibits certain advantages as a scaffold for nanoporous membranes and as a mask for lithographic applications. These advantages include compatibility with a wide range of substrates, ease of control over domain morphologies and remarkable stability, which aid in the development of robust nanoporous networks or high-aspect-ratio patterns. An asymmetric cylinder-forming PS-b-PFS copolymer is subjected to different processing to manipulate the morphology of the phase-separated domains. Control of film structure and domain morphology is achieved by adjusting the film thickness, mode of annealing, and/or annealing time. Changing the process from thermal or solvent annealing to hybrid annealing (thermal and then solvent annealing in sequence) leads to the formation of mesoscale spherulitic and dendritic morphologies. In this communication, we show that reversing the order of the hybrid annealing (solvent annealing first and then thermal annealing) of relatively thick films (> 100 nm) on homogeneously thick substrates develops a discontinuous lamellar structure. Furthermore, the same processing applied on a substrate with a thin, mechanically flexible window in the center leads to the formation of sub-micron scale concentric ring patterns. Enhanced material mobility in the thick film during hybrid annealing along with dynamic rippling effects that may arise from the vibration of the thin window during spin casting are likely causes for these morphologies.
(~175 words) The development of wrinkled polymer thin film structures is viewed optimistically fo... more (~175 words) The development of wrinkled polymer thin film structures is viewed optimistically for the potential development of next generation high-tech devices such as stretchable electronics, microlens arrays, and smart surfaces. Here for the first time, we report a fast, facile method of developing wrinkled patterns where the wrinkles are formed spontaneously, in one step, simply upon solvent casting an azlactone-based polymer onto a substrate, without the need to apply any external stress to the system. The directionality of these wrinkles can be easily tailored by changing the mode of deposition of the polymer films onto the substrates. This methodology is not only simple, but also versatile and robust and could easily be adapted for 3D surfaces and other nonplanar, complex geometries. The persistence of these wrinkles over large distances is apparent, as we have noticed a uniform, sinusoidal wrinkling pattern across the full length of a 12 ” wafer. We expect that this simple, straightforward strategy of wrinkle formation in thin films comprised of a reactive polymer offers myriad possibilities for creating spatially and chemically tailored interfaces for modern
Colloids and Surfaces a Physicochemical and Engineering Aspects, Feb 1, 2010
ABSTRACT The paper summarizes the results of a study on the basic properties (film thickness, con... more ABSTRACT The paper summarizes the results of a study on the basic properties (film thickness, contact angle film/meniscus and gas permeability) of foam films stabilized with the anionic perfluoro octane sulfonate (PFOS) surfactant. The surfactant was used as a tetraethyl ammonium salt. The dependencies on the electrolyte (NH4Cl) and surfactant concentration were studied. Strong dependence of the film thickness and the contact angle on the concentration of NH4Cl and PFOS was observed. Well pronounced transition in the film thickness from common black (electrostatically stabilized) films to Newton black (sterically stabilized) films was registered. The critical salt concentration necessary for the formation of NBF was defined to be 0.1M NH4Cl. The contact angles between the films and the meniscus were collected.The gas permeability coefficient (K, cm/s) was measured at various conditions. The permeability coefficient of NBF decreases with increasing surfactant concentration below the cmc and remains constant above it. The gas permeability of the films depends on the salt concentration, respectively the film thickness in a complicated manner which cannot be explained by simple application of the Fick's law of diffusion.
ABSTRACT Block copolymers with metals confined in one or more blocks are emerging as candidate ma... more ABSTRACT Block copolymers with metals confined in one or more blocks are emerging as candidate materials for nanomanufacturing applications due to their unprecedented nanoscale pattern transfer capabilities. In this article we highlight recent developments in metal-containing block copolymers in terms of their novel synthetic methodologies with particular emphasis on sequential infiltration synthesis, their hierarchical self-assembly from nano, meso, and submicron scales, and their applications as an etch mask for high-throughput, high-aspect-ratio nano and meso scale patterning.
Block copolymers (BCPs) consist of two or more chemically distinct and incompatible polymer chain... more Block copolymers (BCPs) consist of two or more chemically distinct and incompatible polymer chains (or blocks) covalently bonded. Due to the incompatibility and connectivity constraints between the two blocks, diblock copolymers spontaneously self-assemble into microphase-separated nanoscale domains that exhibit ordered 0, 1, 2 or 3 dimensional morphologies at equilibrium. Commonly observed microdomain morphologies in bulk samples are periodic arrangements of lamellae, cylinders, or spheres. Block copolymer lithography refers to the use of these ordered structures in the form of thin films as templates for patterning through selective etching or deposition. The self-assembly and domain orientation of block copolymers on a given substrate is critical to realize block copolymer lithography as a tool for large throughput nanolithography applications. In this work, we survey the morphology of cylinder-forming block copolymers by atomic force microscopy (AFM). Three kind of block copolym...
A series of tree-shaped, amphiphilic dendrimers was synthesized. The products belong to the famil... more A series of tree-shaped, amphiphilic dendrimers was synthesized. The products belong to the family of one-directional arborols of the form ([9]-n), where the notation signifies that each molecule has nine hydroxyl groups ([9]-) as the hydrophilic head and an alkyl chain as the hydrophobic moiety (n = 6, 8, or 10 carbon atoms). The surfactant character changes dramatically as the number of methylene groups increases. The critical micelle concentration of [9]-6 was determined, and pressure-area isotherms of the less soluble [9]-8 and [9]-10 were obtained. Large structures existed atop the spread layers. Large structures were also found in solutions of [9]-6.
ABSTRACT Charge-regulated synthesis of triangular prisms in aqueous solution using self-assembled... more ABSTRACT Charge-regulated synthesis of triangular prisms in aqueous solution using self-assembled polyelectrolyte micelles as templates is described in detail. Micelles formed from amphiphilic polystyrene-block-sulfonated poly(1,3-cyclohexadiene) (PS-b-sPCHD) serve as templates to direct the formation of novel triangular prisms of CuCl2 single crystals. We demonstrate that the edge lengths of these triangular prisms can be easily tailored at room temperature from the nanoscale to the mesoscale by simply adjusting the ratio of charged micelles to protons in the solution. This approach can be extended to the preparation of different ordered crystal structures with a precision hard to achieve via other approaches.
Palladium has been extensively studied as a material for hydrogen sensors because of the simplici... more Palladium has been extensively studied as a material for hydrogen sensors because of the simplicity of its reversible resistance change when exposed to hydrogen gas. Various palladium films and nanostructures have been used, and different responses have been observed with these diverse morphologies. In some cases, such as with nanowires, the resistance will decrease, whereas in others, such as with thick films, the resistance will increase. Each of these mechanisms has been explored for several palladium structures, but the crossover between them has not been systematically investigated. Here we report on a study aimed at deciphering the nanostructure-property relationships of ultrathin palladium films used as hydrogen gas sensors. The crossover in these films is observed at a thickness of approximately 5 nm. Ramifications for future sensor developments are discussed.
Poly(styrene-block-ferrocenyldimethylsilane) (PS-b-PFS) is a metal-containing block copolymer tha... more Poly(styrene-block-ferrocenyldimethylsilane) (PS-b-PFS) is a metal-containing block copolymer that exhibits certain advantages as a scaffold for nanoporous membranes and as a mask for lithographic applications. These advantages include compatibility with a wide range of substrates, ease of control over domain morphologies and remarkable stability, which aid in the development of robust nanoporous networks or high-aspect-ratio patterns. An asymmetric cylinder-forming PS-b-PFS copolymer is subjected to different processing to manipulate the morphology of the phase-separated domains. Control of film structure and domain morphology is achieved by adjusting the film thickness, mode of annealing, and/or annealing time. Changing the process from thermal or solvent annealing to hybrid annealing (thermal and then solvent annealing in sequence) leads to the formation of mesoscale spherulitic and dendritic morphologies. In this communication, we show that reversing the order of the hybrid annealing (solvent annealing first and then thermal annealing) of relatively thick films (> 100 nm) on homogeneously thick substrates develops a discontinuous lamellar structure. Furthermore, the same processing applied on a substrate with a thin, mechanically flexible window in the center leads to the formation of sub-micron scale concentric ring patterns. Enhanced material mobility in the thick film during hybrid annealing along with dynamic rippling effects that may arise from the vibration of the thin window during spin casting are likely causes for these morphologies.
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