Gas transport properties of novel polybenzoxazole (PBO) – silica hybrid membranes with a para-substituted structure were investigated. The para-substituted PBO – silica hybrid membranes were prepared with a para-substituted poly(o-hydroxy amide) as a precursor polymer and tetraethoxysilane (TEOS) via thermal oxazolization and sol-gel processes. The neat para-substituted PBO membranes treated at different temperatures showed higher fractional free volumes than corresponding PBO membranes with a meta-substituted structure reported previously. Gas permeability of the para-substituted PBO – silica hybrid membranes increased with increasing treated temperature and silica content. The increased permeability was brought by increased inter-molecular chain distance and free volume holes formed at the polymer / silica interfaces. It was worth noting that the hybrid membranes showed simultaneous enhancements of CO₂ permeability and CO₂/CH₄ selectivity, suggesting improved size-selective CO₂/CH₄ separation ability by the free volume holes formed at the polymer / silica interfaces. It was concluded the para-substituted PBO – silica hybrid membranes possessed prominent gas permeability and selectivity, and were expected to apply to high-performance gas separation membranes.

Millimeter-thick laminated materials comprised solely of cellulose nanofibers (CNFs) combine optical transparency, high strength, and thermal anisotropy. These CNF laminates were fabricated by stacking thin CNF sheets and applying CNFs dispersed in a water/ethanol mixture as binder, followed by hot pressing. The number of stacked CNF sheets can control the laminate thickness within a wide range of dimensions. Here, we report the correlation between the material properties and laminate thickness of this all-CNF plate material. CNF laminates with different thicknesses (~30-500 μm) were fabricated using 1-15 CNF sheets. The crystallinity of the CNFs in the laminates was greatly enhanced by increasing the number of stacked sheets. This trend in crystallinity is explained by the longer period of time required for drying thicker laminates in the hot press process. The visible-light transmittance of the laminates was well described by the Beer–Lambert law; scattering and/or reflection at the binding interface between sheets were estimated to be negligibly small. The elastic modulus of the laminates increased with increasing number of stacked sheets and reached a maximum of 36 GPa. This increasing trend was explained by the enhanced crystallinity of the CNFs in the laminates. The tensile strengths of the laminates varied greatly, and no clear trend as a function of the number of stacked sheets was found. The thermal conductivity increased with increasing number of stacked sheets, which was attributed to the enhanced crystallinity.

Metal phthalocyanine, a synthetic porphyrin-like compound, has several applications in catalysis. Supported metal phthalocyanine catalysts have attracted increasing attention. In this study, glutaraldehyde (GA) was used for modifying polyvinyl alcohol (PVA) nanofibers by acetalization to improve the water resistance. Subsequently, cobalt tetra (2,4-dichloro-1,3,5-triazine) aminophthalo-cyanine (Co-TDTAPc) was prepared and reacted with OH groups on the surface of the PVA nanofibers to produce Co-TDTAPc–PVA nanofibers. The water resistance test results show that the GA-treated nanofibers demonstrate no significant change in fiber appearance after being soaked in water for 24 h, thus indicating the excellent water resistance of the PVA nanofibers. Moreover, Co-TDTAPc–PVA nanofibers considerably accelerate the degradation of azo fluorescent peach red in the hydrogen peroxide aqueous solution system, and the degradation rate exceeds 98% in 60 min. Furthermore, the nanofibers maintain high catalytic activity after five cycles of tiontesting. These findings indicate that the modified Co-TDTAPc–PVA nanofibers as a navel supported catalyst have a potential application in dye wastewater treatment.