Rina Maeda

Perpendicularly oriented sub-10-nm block copolymer lamellae by atmospheric thermal annealing for one minute

The directed self-assembly (DSA) of block co-polymers (BCPs) can realize next-generation lithography for semiconductors and a variety of soft materials. It is imperative to simultaneously achieve many requirements such as a high resolution, orientation control of micro-domains, etch selectivity, rapid and mild annealing, a low cost, and compatibility with manufacturing for developing suitable BCPs. Here, we describe a new design for modified polysiloxane-based BCPs targeted for sub-10-nm-wide lines, which are able to form perpendicularly oriented lamellar structures in thin films. The hydroxyl groups in the side chains introduced in the polysiloxane block provide a good balance with the polystyrene surface free energy, thereby leading to the perpendicular orientation. Moreover, this orientation can be completed in only one minute at 130 °C in an air atmosphere. Oxygen plasma etching for the thin films results in the achievement of a line width of 8.5 nm.

Well-ordered mesoporous polymers and carbons based on imide-incorporated soft materials

The preparation of well-ordered functional mesoporous polymers through the direct doping and soft templating approach remains challenging and has so far been only limited to specific systems, because of the difficulty to balance the interaction between templates and precursors. Herein we demonstrate the successful preparation of an imide-functionalized mesoporous polymer and its derived nitrogen-doped mesoporous carbon with high regularity, tunable morphology, and high surface area, using highly stable aromatic imide as the nitrogen source. Amic acid, the precursor of imide, undergoes a co-self-assembly process with an amphiphilic block copolymer template and transforms into imide on heating. Upon calcination at 350 °C the template F127 is removed without damaging the imide linkage, leading to a highly ordered polymer network with the intrinsic imide functionality. Further carbonization at 600 °C allows the formation of nitrogen-doped mesoporous carbon. This newly developed system, which exhibits a high degree of flexibility, allows precise morphological control of 1-dimensional lamellar, 2-dimensional hexagonal and 3-dimensional cubic mesostructures on the basis of adjustments of each component in the system. This homologous series of imide functionalized mesoporous polymers and nitrogen-doped mesoporous carbons have potential applications in the field of advanced materials.

Alkylated cage silsesquioxanes: a comprehensive study of thermal properties and self-assembled structure

Derivations of mono-substituted polyhedral oligomeric silsesquioxanes (POSS) with long aliphatic chains were synthesized and self-assembled structures were investigated. The effects of the alkyl chain length and branching on the thermal self-assembling behaviors of the POSS derivatives were examined by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). In addition, small- and wide-angle X-ray scattering (SAXS/WAXS) as well as transmission electron microscopy (TEM) were employed to elucidate their self-assembled morphologies. Long-range straight ordered lamellar structures with sharp boundaries could be reliably formed in the bulk samples of alkylated cage silsesquioxanes by thermal annealing. Furthermore, this research demonstrates an approach to precisely control the feature size at the nanometer scale by carefully tuning parameters of alkyl chain length and branching number.

Perpendicular Orientation Control without Interfacial Treatment of RAFT-Synthesized High-χ Block Copolymer Thin Films with Sub-10 nm Features Prepared via Thermal Annealing

In this study, a series of perpendicular lamellae-forming poly(polyhedral oligomeric silsesquioxane methacrylate-block-2,2,2-trifluoroethyl methacrylate)s (PMAPOSS-b-PTFEMAs) was developed based on the bottom-up concept of creating a simple yet effective material by tailoring the chemical properties and molecular composition of the material. The use of silicon (Si)-containing hybrid high-χ block copolymers (BCPs) provides easy access to sub-10 nm feature sizes. However, as the surface free energies (SFEs) of Si-containing polymers are typically vastly lower than organic polymers, this tends to result in the selective segregation of the inorganic block onto the air interface and increased difficulty in controlling the BCP orientation in thin films. Therefore, by balancing the SFEs between the organic and inorganic blocks through the use of poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) on the organic block, a polymer with an SFE similar to Si-containing polymers, orientation control of the BCP domains in thin films becomes much simpler. Herein, perpendicularly oriented BCP thin films with a χeff value of 0.45 were fabricated using simple spin-coating and thermal annealing processes under ambient conditions. The thin films displayed a minimum domain size of L0 = 11 nm, as observed via atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Furthermore, directed self-assembly (DSA) of the BCP on a topographically prepatterned substrate using the grapho-epitaxy method was used to successfully obtain perpendicularly oriented lamellae with a half pitch size of ca. 8 nm.

Thermally conductive tough flexible elastomers as composite of slide-ring materials and surface modified boron nitride particles via plasma in solution

We have developed a thermally conductive flexible elastomer as a composite material with slide-ring (SR) materials and boron nitride (BN) particles surface-modified via plasma in solution. This composite shows excellent properties as a flexible insulator for thermal management. Surface modification of BN particles using plasma in solution increases the tensile strength, extension ratio at break, toughness, and rubber characteristics of the composites, compared to SR and non-modified BN, while the Youngs modulus values are identical. Furthermore, the thermal conductivity also improved as a result of plasma surface modification.

Synthesis and characterization of self-assembling block copolymers containing fluorine groups

The fluorine-containing block copolymers of poly(styrene-block-2,2,2-trifluoroethyl methacrylate) (PS-b-PTFEMA) and poly(4-hydroxystyrene-block-2,2,2-trifluoroethyl methacrylate) (PHOST-b-PTFEMA), which all are capable of both top-down and bottom-up lithography were developed. The reported block copolymers were synthesized by either anionic polymerization or atom transfer radical polymerization (ATRP). Characterization of bulk and thin films were carried out using differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). Thin films of the resulting block copolymers were subjected to conventional lithographic processing using e-beam and deep-UV radiation to create integrated patterns such as dots in lines.