Effect of UV Pretreatment on the Nanopore Formation within Organosilicate Thin Films

We have investigated the low-temperature cure process to realize nanoporous organosilicate thin films at temperature below 150°C by adding a small amount of photoacid generator PAG followed by UV irradiation. The Gemini surfactant, which decomposes in the temperature range from 170 to 420°C, was used as a pore-generating material porogen for organosilicate matrix. The UV pretreatment in the presence of PAG lowers the condensation temperature of poly methyl silsesquioxane matrix and leads to the fast matrix vitrification enabling the addition of increased amount of porogens. Because the full vitrification of the matrix 150°C by UV pretreatment in the presence of PAG below the decomposition temperature of porogens 170°C prevents the pore collapse, the porosity up to 35.5% was achieved with an average pore size of 3.4 nm, as measured from X-ray reflectivity as well as ellipsometric porosimetry. It is shown that both dielectric constant and refractive index continue to decrease to 2.0 and 1.26, respectively. The present experimental system demonstrates that porogens with low degradation temperature can be successfully incorporated to realize nanoporous films without pore collapse. Consequently, this process can widen the choice of porogens to prepare nanoporous films.This work was supported by the NANO Systems Institute-National Core Research Center (NSI-NCRC) of the Korea Science and Engineering Foundation KOSEF , the Brain Korea 21 Program endorsed by the Ministry of Education of Korea, and System IC 2010 Project of Korea Ministry of Commerce, Industry and Energy

Effect of Interfacial Adhesion on the Mechanical Properties of Organic/Inorganic Hybrid Nanolaminates

Two different kinds of organic polyelectrolyte (PE)/inorganic silicate nanolaminates carrying dissimilar interfacial adhesion between the organic and the inorganic layers were prepared using the layer-by-layer self-assembly. To investigate the mechanical behavior of the prepared hybrid films, apparent modulus (E'), hardness (H), and crack length were measured by depth-sensing nanoindentation as well as a microVickers experiment. The fracture toughness of the hybrid films was then calculated based on the measured mechanical values. In the case of forming strong interfacial adhesion between the organic and the inorganic layers (A series), the fracture toughness and the crack resistance of hybrid multilayer films were significantly improved as a result of the redistribution of stress concentration and the dissipation of fracture energy by the plasticity of organic PE layers. On the other hand, samples with relatively low interfacial adhesion between the organic and the inorganic layers (T series) had little effect on the improvement of fracture toughness of the hybrid films.This work was financially supported by the National Research Laboratory Program (Grant M1-0104-00-0191) and funded in part by the Ministry of Education through the Brain Korea 21 Programs at Seoul National University. Additionaly, this work was supported by the SRC=ERC program of MOST=KOSEF (R11-2005-048-00000-0). B. Y. also acknowledges the financial support through the Seoul Science Fellowship. The X-ray experiments performed at Pohang Light Source were supported by the Ministry of Science and Technology of Korea (MOST)

Effect of Pore Generating Materials on the Electrical and Mechanical Properties of Porous Low-k Films

This work is supported by the NANO Systems Institute-National Core Research Center(NSI-NCRC) from the Korea Science and Engineering Foundation (KOSEF) and System IC 2010 Project of Korea Ministry of Commerce, Industry and Energy. Financial supports from the Ministry of Science and Technology (MOST) and the Korean Ministry of Education through the National Research Laboratory Fund and the Brain Korea 21 Program are also greatly acknowlewdged

Lipid crystals mechanically stimulate adjacent extracellular matrix in advanced atherosclerotic plaques

Objective: Although lipid crystals (LCs) have received attention as a causative factor of plaque rupture, the mechanisms by which they increase plaque vulnerability are unknown. We examined whether solid-state LCs physically affect the adjacent extracellular matrix (ECM) using a combination of multimodal nonlinear optical (MNLO) imaging and finite element analysis (FEA). Methods: The changes of ECMs affected by lipids in atherosclerotic arteries in apolipoprotein E-deficient mice (n=32) fed a high-fat diet for 20-30 weeks were micro-anatomically visualized by a 3D MNLO imaging platform including CARS for lipids, TPEF for elastin, and SHG for collagen. Results and Conclusion: The TPEF signal of elastin was increased at the peripheral regions of LCs (<10μm) compared with foam cell regions. In order to confirm the increase of elastin, biochemical assay (western blot) was performed. The protein level of elastin was increased approximately 2.25-fold (p=0.024) in LC-rich arteries. Under the hypothesis that the increase of elastin resulted from the mechanical stimulus from solid-state LCs, MNLO images were subjected to FEA to simulate the displacement according to the expanding magnitude of the vessel during cardiac cycles. We found that microscale focal stress was increased specifically around the LCs. These FEA results corresponded with the increase of elastin observed by TPEF. These data suggest that LCs mechanically stimulate the adjacent ECM to alter the composition of ECM and cause vessel remodeling. The combination of MNLO imaging and FEA has great potential to verify the mechanical predictions in cardiovascular diseases. © 2014 Elsevier Ireland Ltd.