Teruaki Hayakawa’s research while affiliated with Institute of Science Tokyo and other places

Flower-like particles (FLPs) are highly attractive materials owing to their intricate morphologies and high specific surface areas. However, a definitive method for fabricating organic FLPs with unique three-dimensional morphologies has yet to be established. In this paper, we report on a synthetic route for poly(amic acid) (PAA) FLPs using a specially designed semiaromatic PAA consisting of alternate rigid aromatic segments and flexible alkyl segments via one-step precipitation polymerization at room temperature. The particle morphology can be tuned from spherical to flower-like by adjusting the mixed-solvent ratio. Based on small-angle X-ray scattering, wide-angle X-ray diffraction, and polarized optical microscopy analyses, the flower-like morphology is attributed to the microcrystalline structure formed by the folded and stacked alignment of the PAA precursors. Moreover, solubility plays a crucial role in determining the crystallization rate and growth mechanism, thereby leading to variations in the flower-like morphology. Notably, the flower-like morphology is preserved after thermal imidization and carbonization. The as-synthesized carbon flowers demonstrated high catalytic activity and selectivity for the 2-electron electrochemical reduction of oxygen in an acidic electrolyte, which could be attributed to the N-content of 2.72% and the efficient mass transport granted by the open structure of the unique flower-like morphology.

High-frequency electronic applications increasingly require polymer-based insulators with low dielectric constants ( D k ) and dissipation factors ( D f ). Reducing molecular mobility effectively decreases the D f of polyimides (PIs), which are widely used as interlayer dielectrics in semiconductor integrated circuits. In this study, we reduced molecular mobility by synthesizing smectic liquid crystalline polyimides (LC-PIs) via the use of diamines with phenyl benzoate structures and alkyl chains, and promoting mesogen stacking in LC structures. Self-supporting films were fabricated, and their dielectric properties were evaluated, revealing significantly lower D f values than those of conventional PI. The functional groups responsible for increasing D f are visualized via molecular dynamics simulations performed by applying a virtual alternating electric field to 3D models of the LC-PIs whose structure was confirmed via wide-angle X-ray diffraction. This study highlights the potential of smectic LC-PIs in the molecular design of polymeric materials with lower D f .

Extreme ultraviolet (EUV) lithography currently enables the creation of ultrafine patterns. However, as miniaturization progresses, stochastic defects become a significant challenge. Directed self‐assembly (DSA) of block copolymers (BCPs) has gained attention for pattern rectification to improve the quality of EUV patterns or for density multiplication to obtain sub‐10 nm features. DSA is one of the most promising miniaturization processes because it does not cause stochastic defects. However, dislocation defects are an important issue in density multiplication using strongly segregating BCP. This study demonstrates the use of DSA on 300 mm silicon wafers with higher‐Flory‐Huggins interaction parameter (χ) polystyrene‐block‐poly(methyl methacrylate) derivatives for sub‐10 nm features. These higher‐χ polymers, synthesized from polystyrene‐block‐[poly(glycidyl methacrylate)‐random‐poly(methyl methacrylate)] (PS‐b‐PGM) and 2,2,2‐trifluoroethanethiol (PS‐b‐PGFM), show excellent reproducibility of perpendicular lamellae. Line patterns with a sub‐10 nm half‐pitch are successfully formed by DSA on 300 mm wafers. Line patterns without parallel‐oriented structures or dislocations can be achieved by optimizing the chemical guides and annealing conditions. A polymer with a higher χN value exhibits improved roughness in the resulting line patterns.

Machine learning has rapidly advanced the design and discovery of new materials with targeted applications in various systems. First-principles calculations and other computer experiments have been integrated into material design pipelines to address the lack of experimental data and the limitations of interpolative machine learning predictors. However, the enormous computational costs and technical challenges of automating computer experiments for polymeric materials have limited the availability of open-source automated polymer design systems that integrate molecular simulations and machine learning. We developed SPACIER, an open-source software program that incorporates RadonPy, a Python library for fully automated polymer physical property calculations based on all-atom classical molecular dynamics, into a Bayesian optimization-based polymer design system to overcome these challenges. As a proof-of-concept study, we synthesized optical polymers that surpass the Pareto boundary formed by the tradeoff between the refractive index and the Abbe number.

Mesoporous carbons (MPCs) with a bimodal distribution of pore diameters are more advantageous than their monomodal counterparts for applications in adsorption, catalysis, and drug delivery systems; however, reports on their fabrication remain limited. In this study, we successfully fabricated bimodal MPCs using a soft template method with poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA)-b-poly(4-vinylpyridine) (P4VP)-b-polystyrene (PS) and resol. The blend samples formed microphase-separated structures comprising PTFEMA spheres, PS cylinders, and matrix domains composed of P4VP and resol, leading to the separation of the PTFEMA and PS domains. The P4VP and resol matrix domains were carbonized at a high temperature of 900 °C, whereas the PTFEMA and PS domains were thermally decomposed. This process resulted in bimodal MPCs with both spherical and cylindrical mesopores. The pore diameters calculated using scanning electron microscopy were approximately 10 and 30 nm, while nitrogen adsorption measurements indicated a large specific surface area with a bimodal pore distribution.

The modification of Pt-based cathode catalysts with small molecules has emerged as a promising strategy to enhance their durability in the oxygen reduction reaction (ORR) within proton exchange membrane fuel cells (PEMFCs). This study investigates the efficacy of a novel compound, hexaaza macrocyclic ligand (H 2 HAM), as a modifier anticipated to establish a substantial interaction with the Pt surface. X-ray photoelectron spectroscopy (XPS) analyses, focusing on N1s and Pt4f spectra, reveal a significant electron donation from the ligand to the Pt surface, indicating an improved ligand-Pt interaction. Electrochemical studies demonstrate that the H 2 HAM-modified Pt/C catalyst maintains its electrochemical active surface area (ECSA) and mass-specific activity more durably compared to a pristine Pt/C catalyst. These findings underscore the potential of H 2 HAM as an effective modifier for enhancing the durability of Pt-based cathode catalysts in PEMFC applications. Figure 1

Nitrogen-doped mesoporous carbons are attracting significant attention as next-generation electrocatalytic materials due to their high specific surface area, high electrical conductivity, and exceptional chemical stability. Especially, due to the facilitated mass transport of products, high selectivity for the two-electron oxygen reduction reaction is expected, making it applicable to the synthesis of hydrogen peroxide (H 2 O 2 ).¹ In this study, we focused on the soft template method by utilizing the self-assembly of a block copolymer (BCP) through microphase separation.² In our laboratory, we have been working on the synthesis of poly(4-vinylpyridine)- b -poly(2,2,2-trifluoroethyl methacrylate) (P4VP- b -PTFEMA). The significant repulsive interaction between these two components allows extensive control of the domain size. Furthermore, poly(4-vinylpyridine) serves as both the nitrogen and carbon sources and is selectively crosslinked by resol, thus enabling a high carbonization yield to be obtained. We employed this BCP as a soft template and introduce resol as a cross-linker for fabricating nitrogen-doped mesoporous carbons. Here, we investigated in detail the effects of the composition of the block copolymer and the amount of the crosslinker on the morphology and nitrogen content of the mesoporous carbon. P4VP- b -PTFEMA was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. A mixture of P4VP- b -PTFEMA and resol was dissolved in DMF at 5 wt%, and the solution was evaporated and dried under vacuum at 100 °C for 24 hours to prepare a composite film. Subsequently, the film was heated to 900 °C to fabricate nitrogen-doped mesoporous carbons. Small-angle X-ray scattering (SAXS) analysis of the composite film revealed various microphase-separated structures depending on the BCP-to-resol ratio (Fig. 1 (a)). Furthermore, nitrogen-doped mesoporous carbons with pore diameters ranging from 6.2 nm to 24 nm were fabricated using various molecular weights of PTFEMA (Fig. 1 (b)). Additionally, in our presentation, we will discuss how the pore size affects the selectivity of the two-electron reaction and the catalytic efficiency in the oxygen reduction reaction. [Reference] (1) Park et al ., ACS Catal . 2014 , 4 , 3749. (2) Liu et al. , Polym. Chem. 2014 , 5 , 6452. [Acknowledgement] This study was financially supported by JSPS-KAKENHI(21K04828). Figure 1