Photoinduced Alignment of Nanocylinders by Supramolecular Cooperative Motions
ABSTRACT A linearly polarized laser beam was used to control nanocylinders self-assembled in an amphiphilic diblock liquid-crystalline copolymer consisting of flexible poly(ethylene oxide) as a hydrophilic block and poly(methacrylate) containing an azobenzene moiety in the side chain as a hydrophobic liquid-crystalline segment. The perfect array of poly(ethylene oxide) nanocylinders was achieved, aligned perpendicularly to the polarization direction of the actinic light by supramolecular cooperative motions between the ordered azobenzene and microphase separation. By the simple and convenient way of photocontrol, the macroscopic parallel patterning of nanocylinders can be easily obtained in an arbitrary area.
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- "Zhu et al.  employed the RAFT technique to synthesize polystyrene with a terminal functionalized with an azo structure, and achieved enhanced fluorescence emission after UV irradiation. Ikeda and his coworkers  synthesized an azo-based LC diblock copolymer (PEO-b-PM11AzCN), demonstrating that the supramolecular-ordered nanostructures that can hierarchically assemble in block copolymer films are widely used as templates or scaffolds to prepare nanomaterials according to supramolecular cooperative motions. "
ABSTRACT: This study describes the synthesis of an azobenzene-containing diblock copolymer, poly(StO50-b-Azo7), by using the macro-chain transfer agent StO macro-CTA, and employing sequential reverse addition-fragmentation transfer (RAFT) polymerization. We studied the effects of azobenzene (azo) unit on E/Z photoisomerization, the phase transition temperature, and self-assembly behavior of diblock copolymer, and evaluated the characteristic time involved in the decay process of the photoisomerization kinetics of diblock copolymer. Diblock copolymer poly(StO50-b-Azo7) exhibited moderate thermal stability, with thermal decomposition temperature of 5% weight loss at approximately 340.9 °C, suggesting that the enhancement of the thermal stability was attributed to the incorporation of azo segments into block copolymer. The diblock copolymer showed lower E–Z photoisomerization rates (T1 = 68.0 s) compared with azo monomer (T1 = 10.95 s). Gradually adding water to the tetrahydrofuran (THF) solution of poly(StO50-b-Azo7) produced spherical micelles. Spherical aggregates of poly(StO50-b-Azo7) were obtained (mean diameter = approximately 181.4 nm) by diluting the polymer disperse in a mixture of THF/H2O (water content = 10 vol%), and are shown in TEM images of the diblock copolymer. The results of this study contribute to research on the development of photoresponsive polymer materials.Journal of the Taiwan Institute of Chemical Engineers 03/2015; DOI:10.1016/j.jtice.2015.03.008 · 3.00 Impact Factor
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ABSTRACT: A novel amphiphilic copolymer poly(ethylene glycol)-block-poly(N,N-dimethylamino-2-ethylmethacrylate)-blockpoly[6-(4-methoxy-azobenzene-4′-oxy) hexyl methacrylate] (PEG-b-PDMAEMA-b-PMMAzo) was prepared by ATRP polymerization. The self-assembly and responsive behaviors were investigated by SEM, TEM, LLS and UV-Vis spectra. The results indicated that the copolymers can self-assemble into spherical structures in aqueous media. The aggregate size can be tuned by pH and temperature. The trans-cis isomerization behavior of the formed aggregates was also examined. Upon irradiation with a linear polarized light, the elongation degree of the aggregates was increased with the irradiation time.Chinese Journal of Polymer Science 05/2013; 31(5). DOI:10.1007/s10118-013-1283-y · 1.84 Impact Factor
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ABSTRACT: Photocontrol of molecular alignment is an exceptionally-intelligent and useful strategy. It enables us to control optical coefficients, peripheral molecular alignments, surface relief structure, and actuation of substances by means of photoirradiation. Azobenzene-containing polymers and functionalized liquid crystalline polymers are well-known photocontrollable materials. In this paper, we introduce recent applications of these materials in the fields of mechanics, self-organized structuring, mass transport, optics, and photonics. The concepts in each application are explained based on the mechanisms of photocontrol. The interesting natures of the photocontrollable materials and the conceptual applications will stimulate novel ideas for future research and development in this field.Polymers 03/2012; 4(1). DOI:10.3390/polym4010150 · 3.68 Impact Factor