Self-Seeding in One Dimension: A Route to Uniform Fiber-like Nanostructures from Block Copolymers with a Crystallizable Core-Forming Block

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• 作者：Jieshu Qian ; Yijie Lu ; Anselina Chia ; Meng Zhang ; Paul A. Rupar ; Nikhil Gunari ; Gilbert C. Walker ; Graeme Cambridge ; Feng He ; Gerald Guerin ; Ian Manners ; Mitchell A. Winnik
• 刊名：ACS Nano
• 出版年：2013
• 出版时间：May 28, 2013
• 年：2013
• 卷：7
• 期：5
• 页码：3754-3766
• 全文大小：650K
• 年卷期：v.7,no.5(May 28, 2013)
• ISSN：1936-086X

文摘

One-dimensional micelles formed by the self-assembly of crystalline-coil poly(ferrocenyldimethylsilane) (PFS) block copolymers exhibit self-seeding behavior when solutions of short micelle fragments are heated above a certain temperature and then cooled back to room temperature. In this process, a fraction of the fragments (the least crystalline fragments) dissolves at elevated temperature, but the dissolved polymer crystallizes onto the ends of the remaining seed fragments upon cooling. This process yields longer nanostructures (up to 1 渭m) with uniform width (ca. 15 nm) and a narrow length distribution. In this paper, we describe a systematic investigation of factors that affect the self-seeding behavior of PFS block copolymer micelle fragments. For PI₁₀₀₀-PFS₅₀ (the subscripts refer to the number average degree of polymerization) in decane, these factors include the presence of a good solvent (THF) for PFS and the effect of annealing the fragments prior to the self-seeding experiments. THF promoted the dissolution of the micelle fragments, while preannealing improved their stability. We also extended our experiments to other PFS block copolymers with different corona-forming blocks. These included PI₆₃₇-PFS₅₃ in decane, PFS₆₀-PDMS₆₆₀ in decane (PDMS = polydimethylsiloxane), and PFS₃₀-P2VP₃₀₀ in 2-propanol (P2VP = poly(2-vinylpyridine)). The most remarkable result of these experiments is our finding that the corona-forming chain plays an important role in affecting how the PFS chains crystallize in the core of the micelles and, subsequently, the range of temperatures over which the micelle fragments dissolve. Our results also show that self-seeding is a versatile approach to generate uniform PFS fiber-like nanostructures, and in principle, the method should be extendable to a wide variety of crystalline-coil block copolymers.

Keywords:

crystalline-coil; block copolymers; self-seeding