Symmetric Poly(ethylene oxide-b-styrene-b-isoprene) Triblock Copolymers: Synthesis, Characterization, and Self-Assembly in Bulk and Thin Film

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• 作者：Yali Qiao ; Rachel Ferebee ; Bongjoon Lee ; Indranil Mitra ; Nathaniel A. Lynd ; Jeffery Hayat ; Gila E. Stein ; Michael R. Bockstaller ; Chuanbing Tang
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：September 23, 2014
• 年：2014
• 卷：47
• 期：18
• 页码：6373-6381
• 全文大小：507K
• ISSN：1520-5835

文摘

The synthesis, characterization, and self-assembly of a series of linear poly(ethylene-b-styrene-b-isoprene) (PEO鈭扨S鈭扨I) triblock copolymers containing nearly equal volume fractions of PEO and PI (f_PEO 鈮?f_PI) and various fractions of the middle PS block (70.8 vol % 鈮?f_PS 鈮?75.6 vol %) is reported. A range of azide-functionalized poly(ethylene oxide-b-styrene) diblock copolymers were prepared by atom transfer radical polymerization (ATRP) of styrene using the same batch of PEO-macroinitiator, followed by azide-functionalization. Monohydroxyl-terminated poly(cis-1,4-isoprene) was first alkyne-functionalized and then sequentially attached to azide-functionalized PEO鈭扨S via copper(I)-catalyzed azide鈭抋lkyne cycloaddition reaction, producing PEO鈭扨S鈭扨I triblock copolymers with low dispersity. Bulk samples of each linear triblock copolymer reveal the formation of a binary microdomain structure in which a PS and PI domains mix to form a uniform matrix for spherical PEO microdomains, and the PEO microdomains are arranged in a BCC lattice. Additionally, the thin film ordering of these triblock copolymers was investigated using a high-humidity solvent annealing process, both with and without low concentrations of a lithium salt. The morphology was analyzed by atomic force microscopy and GISAXS, revealing layers of spherical PEO domains arranged with in-plane hexagonal symmetry. The inclusion of salt increased both the size and periodicity of PEO domains.