Photoinduced Morphological Transformations of Soft Nanotubes

• Published in: Chemistry : a European journal Vol. 21; no. 24; pp. 8832 - 8839
• Main Authors: Kameta, Naohiro, Masuda, Mitsutoshi, Shimizu, Toshimi
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 08.06.2015; WILEY‐VCH Verlag; Wiley; Wiley Subscription Services, Inc
• Subjects: Chemistry; Chemistry, Multidisciplinary; Irradiation; Membranes; Micrometers; morphological transformation; Morphology; Nanostructure; Nanotechnology; Nanotubes; photostimulus; Physical Sciences; Residues; Science & Technology; Self assembly; supramolecular chemistry; Transformations; ORGANIC NANOTUBES; TUBES; NANOSTRUCTURES; AMPHIPHILES; ORGANIZATION; nanotubes; self-assembly; GUEST RELEASE; photostimulus; TEMPERATURE; morphological transformation; AZOBENZENE; SUPRAMOLECULAR POLYMERIZATION; POLYGLYCINE-II; supramolecular chemistry
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.201500430

In water, synthetic amphiphiles composed of a photoresponsive azobenzene moiety and an oligoglycine hydrogen‐bonding moiety selectively self‐assembled into nanotubes with solid bilayer membranes. The nanotubes underwent morphological transformations induced by photoisomerization of the azobenzene moiety within the membranes, and the nature of the transformation depended on the number of glycine residues in the oligoglycine moiety (i.e., on the strength of intermolecular hydrogen bonding). Upon UV‐light irradiation of nanotubes prepared from amphiphiles with the diglycine residue, trans‐to‐cis isomerization induced a transformation from nanotubes (inner diameter (i.d.) 7 nm), several hundreds of nanometers to several tens of micrometers in length, to imperfect nanorings (i.d. 21–38 nm). The cis‐to‐trans isomerization induced by continuous visible‐light irradiation resulted in the stacking of the imperfect nanorings to form nanotubes with an i.d. of 25 nm and an average length of 310 nm, which were never formed by a self‐assembly process. Time‐lapse fluorescence microscopy enabled us to visualize the transformation of nanotubes with an i.d. of 20 nm (self‐assembled from amphiphiles with the monoglycine residue) to cylindrical nanofibers with an i.d. of 1 nm; shrinkage of the hollow cylinders started at the two open ends with simultaneous elongation in the direction of the long axis. Ring master: Azobenzene‐modified amphiphiles self‐assembled in water to produce nanotubes (inner diameter (i.d.) 7 mm) with solid bilayer membranes and lengths ranging from nanometers to micrometers. The trans‐to‐cis photoisomerization induced transformation from nanotubes to imperfect nanorings, and cis‐to‐trans photoisomerization generated nanotubes (i.d. 25 mm, average length 310 nm) that consisted of stacked nanorings (see figure).