Mold design rules for residual layer-free patterning in thermal imprint lithography

We present the mold design rules for assuring residual layer-free patterning in thermal imprint processes. Using simple relations for mass balance, structural stability, and work of adhesion, we derive the conditions with respect to the given single or multigeometrical feature of the mold, which are compared with simple thermal imprint experiments using soft imprint molds. Our analysis could serve as a guideline for designing the optimum mold geometry and selecting mold material in residual layer-free thermal imprint processes.     

Synthesis of and ethylene oligomerization with binuclear palladium catalysts having sterically modulated bis-imine ligands with methylene spacer

Sterically modulated bis-imine ligands (L¹-L³) were prepared by reacting 4,4′-methylene bis-(2,6-dialkyl aniline) and antipyrine-4-carboxaldehyde in a 1:2 stoichiometric ratio. The reactions of L¹-L³ with dichloro(cycloocta-1.5-diene)palladium(II) [PdCl₂(cod)] yield the corresponding binuclear palladium complexes with the general formula Pd₂Cl₄L (L = L¹, L², and L³). The binucleating ligands bind to the palladium ion via the lone pair on the imine nitrogen and amide oxygen atoms, resulting in a square-planar geometry around the metal center. All the palladium catalysts efficiently oligomerize ethylene to produce C₄-C₂₀ fractions at activities of up to 1308 kg-oligomer mol-Pd⁻¹ bar⁻¹ h⁻¹ at 30 °C in combination with ethylaluminum sesquichloride. The formation of active sites by the change in geometry of the metal complexes could be traced using spectroscopic and electrochemical techniques.     

A highly porous metal-organic framework: structural transformations of a guest-free MOF depending on activation method and temperature

A doubly interpenetrating porous metal–organic framework ( SNU‐77 ) has been synthesized from the solvothermal reaction of the extended carboxylic acid tris(4′‐carboxybiphenyl)amine (H₃TCBPA) and Zn(NO₃)₂ ? 6H₂O in N,N‐dimethylacetamide (DMA). SNU‐77 undergoes single‐crystal‐to‐single‐crystal transformations during various activation processes, such as room‐temperature evacuation, supercritical CO₂ drying, and high temperature evacuation, to afford SNU‐77R , SNU‐77S , and SNU‐77H , respectively. These guest‐free MOFs exhibited different fine structures with different window shapes and different effective window sizes at room temperature. Variable‐temperature synchrotron single‐crystal X‐ray analyses reveal that the guest‐free structure is also affected by changes in temperature. Despite the different fine structures, SNU‐77R , SNU‐77S , and SNU‐77H show similar gas sorption properties due to the nonbreathing nature of the framework and an additional structural change upon cooling to cryogenic gas sorption temperature. SNU‐77H exhibits a large surface area (BET, 3670 m² g^?1), a large pore volume (1.52 cm³ g^?1), and exceptionally high uptake capacities for N₂, H₂, O₂, CO₂, and CH₄ gases.     

Determination of singlet oxygen quenching and protection of biological systems by various extracts from seed of Rumex crispus L

The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging effect and total phenolic contents were evaluated for the screening of singlet oxygen ((1)O(2)) quenching efficacy of various seed extracts from Rumex crispus L. The butanol and ethyl-acetate extracts displayed remarkable effect of DPPH as compared to positive control ascorbic acid. The concentrations (QC(50)) of butanol and ethyl-acetate extracts required to exert 50% reducing effect on (1)O(2) were found to be 116 and 82 μg mL(-1), respectively. Both extracts were also found to protect the in vitro biological system from the detrimental effect of (1)O(2) on type II photosensitization in Escherichia coli, red blood cell, lactate dehydrogenase and histidine. Among all the tested extracts, the ethyl-acetate and butanol extracts contained higher amount of total phenolic contents. The results suggest that our study may contribute to the development of new bioactive products with potential applications to reduce photo-produced oxidative stress involving reactive oxygen species in living organisms.     

Micropatterning of proteins on ion beam‐induced poly(acrylic acid)‐grafted polyethylene film

Micropatterns of proteins were created by using patterned ion beam irradiation onto a polyethylene film and graft polymerization of acrylic acid. Acrylic acid was selectively graft polymerized on the irradiated regions. The results of the grafting study revealed that the optimum fluence to achieve the maximum grafting degree was 1 × 10¹⁵ ions/cm². Biotin was covalently immobilized on the grafted regions of the polyethylene film. Protein patterning was achieved through specific binding of biotin and streptavidin. The resolved protein patterns with the maximum fluorescence intensity were achieved on the poly(acrylic acid) (PAA)‐grafted polyethylene films prepared at the fluence of 1 × 10¹⁵ ions/cm². This method can be used for patterning of various biomolecules and for further biological applications. Copyright © 2010 John Wiley & Sons, Ltd.     

Encapsulation and Stabilization of Photo‐Sensitive Antioxidants by Using Polymer Microcapsules with Controlled Phase Heterogeneity

We describe a robust method for both encapsulating and stabilizing photo‐sensitive antioxidants in polymer microcapsules prepared by a water‐in‐oil‐in‐water double emulsification and evaporation technique, in which a volatile solvent from the oil layer consisting of poly(methyl methacrylate) and methylene chloride is gradually removed. Using poly(ethylene glycol) (PEG) in this study, we demonstrate that control over its molecular weight allows to tune the phase property of the capsule wall; introducing PEG with high molecular weight results in increased heterogeneity. The heterogeneity of the capsule walls displays an ability to effectively block sunlight, which is essential for improving the molecular stability of photo‐sensitive antioxidants. In this study, we experimentally confirm this by observing natural sunlight‐driven molecular decomposition of a model antioxidant, riboflavin‐5′‐phosphate, in poly (methyl methacrylate) microcapsules.

     

Real hypersurfaces in complex two-plane Grassmannians with commuting Ricci tensor

In this paper, first we introduce the full expression for the Ricci tensor of a real hypersurface M$M$ in complex two-plane Grassmannians _G2(C^m+2)$G_2\left({\mathbb{C}}^{m+2}\right)$ from the equation of Gauss. Next we prove that a Hopf hypersurface in complex two-plane Grassmannians _G2(C^m+2)$G_2\left({\mathbb{C}}^{m+2}\right)$ with commuting Ricci tensor is locally congruent to a tube of radius r$r$ over a totally geodesic _G2(C^m+1)$G_2\left({\mathbb{C}}^{m+1}\right)$. Finally it can be verified that there do not exist any Hopf Einstein hypersurfaces in _G2(C^m+2)$G_2\left({\mathbb{C}}^{m+2}\right)$.     

Ab initio studies of the intramolecular amide hydrolysis in N-methylmaleamic acids

The intramolecular amide hydrolysis reactions of N-methylmaleamic acids (NMMA) are studied at the MP2/6-31G**//RHF/4-31G level of theory as model reactions of peptide bond cleavage by a proteolytic enzyme. In contrast to the previously reported results for a bimolecular reaction model of peptide hydrolysis, the unimolecular reactions studied here proceed via the concerted pathway in which the C–O bond formation and the release of methylamine occur simultaneously in preference to the stepwise one. The determination of an intrinsic reaction coordinate shows that the reaction is facilitated by the intramolecular proton transfer from the undissociated carboxyl group to the nitrogen of the leaving amine group. Mainly because of the increase in activation energy, methyl substitution at the 2-position retards the hydrolysis reaction rate by a factor of 14 compared to the reaction of the unsubstituted molecule. In contrast, additional methyl substitution at 3-position leads to 35-fold increase in the reaction rate. These variations of reactivity are caused by the charge redistributions in the amide group induced by methyl substitutions and the resulting changes in electrophilicity of the aminocarbonyl carbon.     

Microphase‐separated structure of telechelic urethane acrylate anionomers and their network in various solvents

Telechelic urethane acrylate anionomer (UAA) chain showed less viscosity and polyelectrolyte behavior in water than dimethyl acetamide (DMAc) because of hydrophobic aggregation. UAA networks prepared in different solvents (water and DMAc) exhibited very different swelling behaviors in the same swelling medium, which can be interpreted as due to the very different microstructures formed in the solvents. UAA networks prepared with water (UAHG networks) had microphase‐separated hydrophilic and hydrophobic domains, whereas UAA networks synthesized with DMAc (UADG networks) had relatively homogeneous network structures. The mechanical property of the UAHG and UADG networks, measured with a dynamic mechanical analyzer, was also very sensitive to the solvent type used during the crosslinking reaction. UAHG networks with a microphase‐separated structure had a higher modulus than UADG networks. The results of the mechanical property measurements showed that water was a much better solvent for the hydrophilic hard segments of UAA chain than DMAc, even though DMAc dissolved both hydrophilic and hydrophobic segments of UAA chain. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2081–2095, 2000