Photo-Induced Micellization of Block Copolymers

Abstract

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 1 H 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. OPEN ACCESSPolymers 2010, 2 624

Positive‐tone photoresist consisting of a multifunctional acrylate resin that can be patterned after photo‐crosslinking

“…It is considered that the crosslinked structure in the frozen PPaP underwent acid catalyzed degradation and becomes soluble in a TMAH solution (Scheme ). TPST, which is widely used for chemically amplified deep UV photoresist, generates acid at wavelengths much shorter than 300 nm . The acid catalyzes degradation of tertiary ester linkages in the resin, and the degradation produces alkaline soluble carboxylic acid derivatives together with 2,5‐dimethyl‐2,4‐hexadiene …”

“…TPST, which is widely used for chemically amplified deep UV photoresist, generates acid at wavelengths much shorter than 300 nm. 35 The acid catalyzes degradation of tertiary ester linkages in the resin, and the degradation produces alkaline soluble carboxylic acid derivatives together with 2,5-dimethyl-2,4-hexadiene. 4 Changes in the film structure before and after decomposition were analyzed by FTIR.…”