Ki-Ho Nam

Herein, we present a strategy for designing thermally stable adhesive compositions that synergistically balance hydrogen-bond-mediated interfacial adhesion with network-derived bulk cohesion. Complementary hydrogen bonding between carbazole- and benzophenone-based bismaleimides (BMIs) establishes a cohesive molecular framework, while 2,2′-diallylbisphenol A (DABPA)-mediated allyl–maleimide ene reactions regulate network evolution to alleviate brittleness and improve processability. Subsequent incorporation of low-viscosity epoxy prepolymer promotes substrate wetting and generates hydroxyl functionalities during curing while yielding an interpenetrating polymer network. Nonisothermal differential scanning calorimetry analyses of the BMI compositions revealed pseudo-first-order curing behavior, and kinetic modeling demonstrated composition-dependent curing kinetics that govern curing reactivity and melt processability. With the subsequent incorporation of 30 phr of epoxy prepolymer, BMI–DABPA exhibited a low melt viscosity of 0.019 Pa·s, providing sufficient fluidity for resin spreading and substrate wetting. The resulting complementary hydrogen-bonded dual-network BMI adhesive delivered a lap shear strength of 11.53 MPa on an Fe substrate while maintaining excellent thermal stability (Td5% > 407 °C; char yield >43% at 800 °C). This work demonstrates the potential of balancing adhesion, cohesion, and processing characteristics in BMI adhesives by designing a reactive monomer system of sufficiently low viscosity, providing a rational molecular design strategy for future developments.

Antibacterial properties are as critical as filtration efficiency in water treatment membranes, as they determine longevity and biofouling resistance. This study reports the fabrication of flexible antibacterial films featuring an in situ fluorine‐doped laser‐induced graphene (F‐LIG) surface, generated via direct CO ₂ laser writing on fluorinated polyimide (F‐PI) substrates. By adjusting laser parameters, the surface wettability of F‐LIG is tuned from hydrophilic to highly hydrophobic (contact angle: 131.5°). The hydrophobic F‐LIG exhibited synergistic antibacterial activity through (1) chemical inhibition, where fluorination‐induced low surface energy suppressed bacterial adhesion, and (2) physical disruption, where nanoscale roughness mechanically damaged bacterial cells. Antibacterial tests against Escherichia coli and Staphylococcus aureus demonstrated up to 80.7% bacterial removal, surpassing the hydrophilic variant. Furthermore, a bacterial‐responsive Janus membrane is fabricated by combining an F‐LIG top layer with a porous fluorinated polyimide (F‐PPI) substrate, prepared via non‐solvent‐induced phase separation (NIPS). Permeability and dye removal experiments using pigment blue 15:3 and methylene blue revealed that the porous F‐LIG membranes achieved removal efficiencies of up to 96.3% and 83.9%, respectively, despite slightly lower permeability than commercial PVDF filter paper. These results highlight the promise of F‐LIG‐based membranes that integrate antibacterial and filtration functions within a single platform.

Water pollution is an inevitable concern associated with technological advancement. To address this problem, it is necessary to significantly shorten the manufacturing process of porous materials while enabling effective pollutant removal. Herein, a facile, rapid, and scalable approach is reported to obtain sulfur‐doped hierarchically porous laser‐induced graphene (S‐LIG) as a catalytic membrane with three‐dimensional networks by localized laser irradiation, along with possible adsorption and electrochemical degradation mechanisms for pollutant removal. S‐LIG is derived from sulfur‐containing porous polyimide film which is prepared via thermally induced phase separation followed by stepwise thermal imidization. Methylene blue (MB) adsorption behavior on the S‐LIG membrane closely fits the pseudo‐second‐order and Freundlich isotherm models, suggesting a complex sorption mechanism, including both strong chemical interaction and physical adsorption. Furthermore, S‐doping enhances catalytic activity for generating reactive oxygen species (ROS), aiding MB degradation via indirect oxidation, and improves direct oxidation on the anode by accelerating electron transfer at the electrodes. This results in a stable 93% MB degradation at a low 1.5 V after 24 h. Additionally, the impact of solution pH reveals that electrostatic attraction forces under basic conditions and the high generation of ROS under acidic conditions favor adsorption and electrochemical oxidation.

Phenylethynyl-terminated imide (PETI) oligomers are highly valued for their diverse applications in films, moldings, adhesives, and composite material matrices. PETIs can be synthesized at varying molecular weights, enabling the fine-tuning of their properties to meet specific application requirements. Upon thermal curing, these oligomers form super-rigid network structures that enhance solvent resistance, increase glass-transition temperatures, and improve elastic moduli. Their low molecular weights and melt viscosities further facilitate processing, making them particularly suitable for composites and adhesive bonding. This review examines recent advancements in developing ultra-high-temperature PETIs, focusing on their structure–processing–properties relationships. It begins with an overview of the historical background and key physicochemical characteristics of PETIs, followed by a detailed discussion of PETIs synthesized from monomers featuring noncoplanar configurations (including kink and cardo structures), fluorinated groups, flexible linkages, and liquid crystalline mesogenic structures. The review concludes by addressing current challenges in this research field and exploring potential future directions.

Polymers with a low dielectric constant (D_k) are promising materials for high-speed communication networks, which demand exceptional thermal stability, ultralow D_k and dissipation factor, and minimum moisture absorption. In this paper, we prepared a series of novel low-D_k polyimide films containing an MCM-41-type amino-functionalized mesoporous silica (AMS) via in situ polymerization and subsequent thermal imidization and investigated their morphologies, thermal properties, frequency-dependent dielectric behaviors, and water permeabilities. Incorporating 6 wt.% AMS reduced the D_k at 1 MHz from 2.91 of the pristine fluorinated polyimide (FPI) to 2.67 of the AMS-grafted FPI (FPI-g-AMS), attributed to the free volume and low polarizability of fluorine moieties in the backbone and the incorporation of air voids within the mesoporous AMS particles. The FPI-g-AMS films presented a stable dissipation factor across a wide frequency range. Introducing a silane coupling agent increased the hydrophobicity of AMS surfaces, which inhibited the approaching of the water molecules, avoiding the hydrolysis of Si–O–Si bonds of the AMS pore walls. The increased tortuosity caused by the AMS particles also reduced water permeability. All the FPI-g-AMS films displayed excellent thermooxidative/thermomechanical stability, including a high 5% weight loss temperature (>531 °C), char residue at 800 °C (>51%), and glass transition temperature (>300 °C).

The manufacturing of fiber-reinforced plastics has been linked to the discharge of volatile organic compounds (VOCs), particularly toluene and benzene, which have been identified as posing substantial risks to human health and the environment. To counteract this issue, activated carbons have been suggested as a means of reducing VOC emissions through adsorption. The objective of this study was to investigate the adsorption characteristics of toluene and benzene onto activated carbons produced from coal (AC) and coconut shells (CAC). The study was carried out in an aqueous medium. The findings revealed that the AC sample with higher surface characteristics exhibited a higher adsorption capacity (toluene: 196.0784 mg g⁻¹ and benzene: 181.8182 mg g⁻¹) in comparison to the CAC sample (toluene: 135.1351 mg g⁻¹ and benzene: 116.2791 mg g⁻¹). The superior adsorption performance of AC on both VOCs can be attributed to its higher surface characteristics. The Langmuir model was found to be more appropriate than the Freundlich model, as indicated by the higher coefficient of determination (R²) value of the Langmuir isotherm (avg. R² = 0.9669) compared to that of the Freundlich isotherm (avg. R² = 0.9654), suggesting the use of a monolayer adsorption mechanism. The adsorption kinetics of the samples were analyzed using the pseudo-first-order and pseudo-second-order models, and the former was found to be more fitting, indicating that the rate of adsorption is directly proportional to the concentration difference between the solution and the sample surface. The adsorption process was found to be spontaneous and favorable based on the positive value of ΔG_ads. Furthermore, the adsorption process was endothermic and disordered, as indicated by the positive values of ΔH_ads and ΔS_ads. The regeneration efficiency of all the samples was secured more than 95% upon the fifth cycle.