Plate waves in Hadamard materials

The dispersion equation for elastic waves of small amplitude in a pre-stressed plate of restricted Hadamard material is derived and its solutions are investigated in detail. The implications for stability are discussed.     

Synthesis and Characterization of Diastereoisomerically Pure Tetracyclo[6.2.1.13,6.02,7]dodec‐9‐ene‐4‐carboxylic Acid Derivatives

The synthesis and detailed NMR analysis of diastereoisomerically pure samples of 4‐methyltetracyclo[6.2.1.1^3,6.0^2,7]dodec‐9‐ene‐4‐carboxylic acid ( 2 ), tetracyclo[6.2.1.1^3,6.0^2,7]dodec‐9‐ene‐4‐carboxylic acid ( 6 ) and their tert‐butyl esters are reported. Mixtures containing two isomers of the methyl esters of these compounds were obtained by a twofold, sequential Diels‐Alder reaction between cyclopentadiene, and methyl methacrylate or methyl acrylate, respectively. Pure diastereoisomers of the acids were prepared by selective hydrolysis of their methyl esters.     

Design of photoresists with reduced environmental impact. II. Water‐soluble resists based on photocrosslinking of poly(2‐isopropenyl‐2‐oxazoline)

The performance of water‐ and solvent‐cast, two‐component photoresist films containing poly(2‐isopropenyl‐2‐oxazoline) or poly(2‐isopropenyl‐2‐oxazoline‐co‐styrene) with a photoacid generator has been investigated. These materials afford negative‐tone images after deep‐UV exposure and development in a suitable medium (water or toluene). Resist solutions prepared from polymers containing at least 80 mol % 2‐isopropenyl‐2‐oxazoline may be cast from and developed in pure water. Features of higher quality can be obtained when the resist is cast from 2‐methoxyethanol, probably because side reactions such as partial hydrolysis of the pendant oxazoline rings in aqueous environments are avoided. It was possible to resolve micrometer scale patterns using ca. 200 mJ/cm² of irradiation at 254 nm, followed by heating 2 min at 130°C and development in water alone. Image quality and etch resistance were improved using copolymers containing up to 20 mol % of styrene repeat units. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1225–1236, 1999     

Molecular model of phenolic polymer dissolution in photolithography

The resolution of photolithographic processes has advanced to the point that difficulties, such as line‐edge roughness, associated with phenomena occurring at molecular length scales are becoming important. In order to control these phenomena, it is necessary to understand them. To that end, a numerical model has been used to simulate the dissolution of phenolic polymers in aqueous base. The simulation applies the Critical Ionization Model to a rectangular‐lattice representation of the polymer matrix. The model has been adapted to describe the dissolution process that is responsible for photoresist function. Both continuum and molecular versions of the model are presented. The Continuum Model yields dissolution profiles that approximate the contours of the calculated spatial variations in chemical blocking (blocking profile). An algorithm has been developed to connect individual cells to form polymer chains, and to fill the lattice in a way that produces a Gaussian chain length distribution. The model employs only a single adjustable parameter, the time‐step correction factor (assuming one can measure the probability of ionization once a site encounters the developer). The Molecular Model predicts a dissolution rate that decreases non‐linearly with respect to degree of chemical blocking, as is observed experimentally. Dissolution profiles can be generated with the Molecular Model based either on this calculated dependence of the dissolution rate on blocking fraction or from direct application of the model to a blocking profile. The probabilistic nature of the model introduces edge roughness of the same degree as that observed experimentally. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2103–2113, 1999     

Design of high-χ block copolymers for lithography

This report describes the design and synthesis of a series of lamella-forming, silicon-containing block copolymers (Si-BCPs) and evaluation of these materials as potential candidates for lithographic applications. The interaction parameter χ of each Si-BCP is measured by both the mean-field theory predicted order-disorder transition and by analysis of X-ray scattering profiles. The introduction of more-polar methoxy and less-polar methylsilyl moieties increases χ to about 2–3 times that of the reference material, poly(styrene-block−4-trimethylsilylstyrene). The incremental increases appear to be essentially additive in this family of block copolymers, suggesting that improvements in χ can be predicted from appropriate monomer choice. Perpendicularly oriented thin-films of the ordered Si-BCPs generated by thermally annealing between two “neutral” polymeric surfaces and developed by etching on commercial RIE equipment show excellent image fidelity. These images demonstrate the excellent etch contrast of the Si-BCPs and document improvements in pattern fidelity that are realized with more strongly segregated BCPs. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 344–352     

Basic flows of a micropolar liquid

Steady plane shear flow, rotation flow, plane wave disturbances, oscillatory boundary layers, and free surface waves in a micropolar liquid are investigated.     

Preparation and characterization of MgB2 superconductor

The MgB₂ superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties. The upper critical field, irreversibility line and critical current density have been determined using magnetization data. The current-voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition. The surface analysis using X-ray photoelectron spectroscopy shows that MgB₂ is sensitive to atmospheric degradation.