Polymeric materials have been extensively utilized as electron transport (n-type) materials in organic solar cells instead of conventional fullerene derivatives due to their superior optoelectronic properties and stability. Among them, polymers with a structure comprising fused heterocyclic multi-ring aromatic units, and branched alkyl side chains ensuring solubility have been focused on. However, from the perspective of electron transport, the branched alkyl chains might hinder the stacking of conjugated systems. We proposed the molecular design, where highly flexible oxyethylene groups as side chains are incorporated aiming to achieve an optimal balance between electron mobility and solubility. We synthesized the conjugated polymer, P(NDI2O4C6-T2) consisting of naphthalene dimide as the main chain, and linear hexyl tetra(oxyethylene) group as the side chain (3, 6, 9, 12-tetraoxaoctadecyl group), and evaluated the basic properties including electron mobility. For comparison, analogues with linear octyl and branched 2-octyldodecyl groups, P(NDI2C8-T2) and P(NDI2OD-T2) were also prepared. Consequently P(NDI2O4C6-T2) exhibited the highest electron mobility and solubility in conventional organic solvents. Quantum chemical calculations were also carried out to verify the experimental results based on the intra- and intermolecular interaction in the polymer.

This study investigates the integration of polarizing dyes, commonly used in LCDs and polarized sunglasses, into yarns and textiles to evaluate their optical properties and explore potential applications in clothing. The high-temperature-resistant polarizing dyes, stable above 300°C, facilitated the production of colored polyester yarns via melt spinning. Initially, monofilament yarns in five colors (Yellow, Red, Blue, Cyan, Black) were created and their polarizing properties were assessed. Polarizing microscopic observations showed distinct variations in light absorption and reflection, depending on the yarn’s alignment with the polarizer. Colors appeared darker when the yarn was perpendicular and lighter when parallel to the polarizer, confirming the alignment of the longitudinal direction of the yarn and polarizing dye with the light absorption axis. Using a UV-Vis spectrophotometer (Shimadzu UV-2450) with a commercial polarizing film (99% polarization degree), a practical method was established to evaluate the degree of polarization. The monofilament yarns were compatible with embroidery machines, allowing the creation of samples with unique optical effects. Hidden images were created by stitching directionally with polarizing films. Furthermore, multifilament yarns were developed, twisted, and woven into textiles using a commercial Jacquard loom. These textiles exhibited significant differences in light transmission and reflection when observed with a polarizing film. Even without the polarizing film, the textiles displayed unique visual effects based on their orientation and light angle. The findings suggest that polarized textiles have great potential for innovative applications in fashion and costume design.