화학공학소재연구정보센터
Journal of Polymer Science Part A: Polymer Chemistry, Vol.54, No.12, 1852-1863, 2016
Poly(N-vinyl pyrrolidone)-block-Poly(N-vinyl carbazole)-block-Poly(N-vinyl pyrrolidone) Triblock Copolymers: Synthesis via RAFT/MADIX Process, Self-Assembly Behavior, and Photophysical Properties
Poly(N-vinyl pyrrolidone)-block-poly(N-vinyl carbazole)-block-poly(N-vinyl pyrrolidone) (PVP-b-PVK-b-PVP) triblock copolymers were synthesized via sequential reversible addition-fragmentation chain transfer/macromolecular design via the interchange of xanthate (RAFT/MADIX) process. First, 1,4-phenylenebis(methylene) bis(ethyl xanthate) was used as a chain transfer agent to mediate the radical polymerization of N-vinyl carbazole (NVK). It was found that the polymerization was in a controlled and living manner. Second, one of a, x-dixanthate-terminated PVKs was used as the macromolecular chain transfer agent to mediate the radical polymerization of N-vinyl pyrrolidone (NVP) to obtain the triblock copolymers with various lengths of PVP blocks. Transmission electron microscopy (TEM) showed that the triblock copolymers in bulks were microphase-separated and that PVK blocks were self-organized into cylindrical microdomains, depending on the lengths of PVP blocks. In aqueous solutions, all these triblock copolymers can self-assemble into the spherical micelles. The critical micelle concentrations of the triblock copolymers were determined without external adding fluorescence probe. By analyzing the change in fluorescence intensity as functions of the concentration, it was judged that the onset of micellization occurred at the concentration while the FL intensity began negatively to deviate from the initial linear increase with the concentration. Fluorescence spectroscopy indicates that the self-assembled nanoobjects of the PVP-b-PVK-b-PVP triblock copolymers in water were capable of emitting blue/or purple fluorescence under the irradiation of ultraviolet light. (C) 2016 Wiley Periodicals, Inc.