Order鈥揙rder Transition between Equilibrium Ordered Bicontinuous Nanostructures of Double Diamond and Double Gyroid in Stereoregular Block Copolymer

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• 作者：Che-Yi Chu ; Wen-Fu Lin ; Jing-Cherng Tsai ; Chia-Sheng Lai ; Shen-Chuan Lo ; Hsin-Lung Chen ; Takeji Hashimoto
• 刊名：Macromolecules
• 出版年：2012
• 出版时间：March 13, 2012
• 年：2012
• 卷：45
• 期：5
• 页码：2471-2477
• 全文大小：357K
• 年卷期：v.45,no.5(March 13, 2012)
• ISSN：1520-5835

文摘

While ordered bicontinuous double diamond (OBDD) in block copolymers has always been considered as an unstable structure relative to ordered bicontinuous double gyroid (OBDG), here we report the existence of a thermodynamically stable OBDD structure in a diblock copolymer composed of a stereoregular block. A slightly asymmetric syndiotactic polypropylene-block-polystyrene (sPP-b-PS) as cast from xylene was found to display the OBDD morphology. When the OBDD-forming diblock was heated, this structure transformed to the OBDG phase at ca. 155 掳C. Interestingly, OBDD was recovered upon cooling even in the temperature range above melting point of sPP, indicating that OBDD was a thermodynamically stable structure for sPP-b-PS melt, which was in contradiction to the conventional view. We propose that the larger free energy cost encountered in OBDD due to the larger packing frustration may be compensated sufficiently by the release of free energy due to local packing of the conformationally ordered segments of sPP blocks, which stabilizes the OBDD structure at the lower temperatures.