Abstract
Creation of hollow, one-dimensional nanomaterials has gained great recent attention in the chemical and material sciences. In a study aimed at discovering new functional materials of this type, we observed that an amphiphilic diacetylene (DA) derivative, containing an azobenzene moiety and an oligo-ethylene group, self-assembles to form nanotubes and undergoes photopolymerization to form hollow polydiacetylene (PDA) nanotubes with a uniform wall thickness and diameter. The azobenzene-PDA nanotubes are photoresponsive in that on-and-off UV-irradiation leads to a reversible morphological change between straight and bent forms in association with E-Z photoisomerization of the azobenzene group. Owing to the UV-induced structural change feature, the new DA and PDA nanotubes serve as a controlled release material. Accordingly, fluorescent rhodamine B encapsulated inside the nanotubes are effectively released by using repeated on-off UV irradiation. Furthermore, photo-release of rhodamine B was shown to occur in an artemia (brine shrimp).
Highlights
Polydiacetylenes (PDAs), a family of structurally and optically unique conjugated polymers, can be readily prepared by polymerization of well-ordered assemblies of diacetylenes (DAs)[1,2,3,4,5,6,7,8,9,10]
The light yellow precipitate was photopolymerized by 254 nm UV irradiation, resulting in a blue color, which is a typical characteristic of self-assembled DAs
In the investigation described above, we developed an effective approach for fabricating a photoresponsive PDA nanotube that has a uniform wall thickness and diameter
Summary
Polydiacetylenes (PDAs), a family of structurally and optically unique conjugated polymers, can be readily prepared by polymerization (typically 254 nm UV-irradiation, heat treatment or electric pulse) of well-ordered assemblies of diacetylenes (DAs)[1,2,3,4,5,6,7,8,9,10]. It was observed that DA-Azo-TEG nanotubes dispersed in a solution of 1:1 (v/v) ethanol-water display a light yellow color, which changes to blue upon irradiation with 254 nm light. When gradually heated from ambient temperature to 90 °C, the color change from blue to red was observed in the PDA-Azo-TEG nanotube dispersion (Fig. 3c).
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