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Photo-Induced Micellization of Block Copolymers
Department of Environmental and Life Sciences, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi 441-8580, Japan
Department of Materials Science, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi 441-8580, Japan
* Author to whom correspondence should be addressed.
Received: 30 September 2010; in revised form: 16 November 2010 / Accepted: 25 November 2010 / Published: 26 November 2010
Abstract: We found novel photo-induced micellizations through photolysis, photoelectron transfer, and photo-Claisen rearrangement. The photolysis-induced micellization was attained using poly(4-tert-butoxystyrene)-block-polystyrene diblock copolymer (PBSt-b-PSt). BSt-b-PSt showed no self-assembly in dichloromethane and existed as isolated copolymers. Dynamic light scattering demonstrated that the copolymer produced spherical micelles in this solvent due to irradiation with a high-pressure mercury lamp in the presence of photo-acid generators, such as bis(alkylphenyl)iodonium hexafluorophosphate, diphenyliodonium hexafluorophosphate, and triphenylsulfonium triflate. The 1H NMR analysis confirmed that PBSt-b-PSt was converted into poly(4-vinylphenol)-block-PSt by the irradiation, resulting in self-assembly into micelles. The irradiation in the presence of the photo-acid generator also induced the micellization of poly(4-pyridinemethoxymethylstyrene)-block-polystyrene diblock copolymer (PPySt-b-PSt). Micellization occurred by electron transfer from the pyridine to the photo-acid generator in their excited states and provided monodispersed spherical micelles with cores of PPySt blocks. Further, the photo-Claisen rearrangement caused the micellization of poly(4-allyloxystyrene)-block-polystyrene diblock copolymer (PASt-b-PSt). Micellization was promoted in cyclohexane at room temperature without a catalyst. During micellization, the elimination of the allyl groups competitively occurred along with the photorearrangement of the 4-allyloxystyrene units into the 3-allyl-4-hydroxystyrene units.
Keywords: micellization; photolysis; photoelectron transfer; photo-claisen rearrangement; self-assembly; micelles; photo-acid generators; block copolymers
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Cite This Article
MDPI and ACS Style
Yoshida, E.; Kuwayama, S. Photo-Induced Micellization of Block Copolymers. Polymers 2010, 2, 623-648.
Yoshida E, Kuwayama S. Photo-Induced Micellization of Block Copolymers. Polymers. 2010; 2(4):623-648.
Yoshida, Eri; Kuwayama, Satoshi. 2010. "Photo-Induced Micellization of Block Copolymers." Polymers 2, no. 4: 623-648.