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We studied the elongational crystallization of poly(ethylene terephthalate) (PET) from the supercooled melt. We found that the novel three-dimensional (3D) structure of “nano-oriented crystals (NOCs)” was formed, where nanocrystals (NCs) were arranged on monoclinic lattice. We observed the structure and morphology of NOCs by means of polarizing optical microscope and small/wide angle X-ray scatterings. We clarified the important role of a primary structure of the plate-like benzene ring in the formation of the NOCs of PET. We also showed high performance of NOCs of PET, such as high heat resistance temperature and high maximum tensile stress.
The gas transport properties of polybenzoxazole (PBO)–silica hybrid membranes were investigated. The gas permeability of the PBO–silica hybrid membranes increased withincreasing silica content and thermal treatment temperature. The hybrid membranes prepared with tetraethoxysilane (TEOS) showed simultaneous enhancements in CO2 permeability and CO2/CH4 selectivity with increasing silica content and thermal treatment temperature. The prominent CO2/CH4 separation ability might be attributable to free volume holes created around the polymer/silica interfacial area and increased intermolecular chain distance.
Synthesis and properties of borafluorene-containing conjugated polymers with various comonomers are presented. From the comparison with the gallafluorene copolymers, higher luminescent quantum yields were obtained from the borafluorene copolymers. Additionally, from the electrochemical measurements, it was shown that the electron-withdrawing property of the boron atoms led to the stabilization of LUMOs of the borafluorene copolymers. In the X-ray diffraction profiles, the significant peaks originated from π−π stacking and assembly of the side chains were observed. The borafluorene copolymers were more crystalline materials relative to the gallafluorene polymers.
The thermoresponsive copolymer P(MEO2MA-co-OEGMA500) was successfully prepared using a novel photopolymerization procedure. The synthesis was carried out using a user-friendly method with a few ppm of a photoredox iridium-based catalyst. Monomer conversions higher than 50% were achieved in less than 1 h of synthesis showing a faster polymerization rate when compared to the traditional Cu-based ATRP synthesis. The photochemically controlled method here described provides true control over polymer structure, architecture, and properties. Furthermore, the polymer showed no toxicity on four mammalian cell lines at the highest concentration tested (0.4 mg/ml).
A facile and practical surface-engineering methodology to enhance the self-assembly of PS-b-PDMS BCPs with high χ by precisely controlling the molecular weight and weight percent of PS brushes. Highly ordered sub-20-nm BCP patterns were successfully obtained in a few minutes under the optimum PS brush condition.