Current-Induced Formation of Gradient Crystals in Block Copolymer Electrolytes
详细信息 查看全文
- 作者：Scott A. Mullin ; Gregory M. Stone ; Alexander A. Teran ; Daniel T. Hallinan ; A. Hexemer ; Nitash P. Balsara
- 刊名：Nano Letters
- 出版年：2012
- 出版时间：January 11, 2012
- 年：2012
- 卷：12
- 期：1
- 页码：464-468
- 全文大小：262K
- 年卷期：v.12,no.1(January 11, 2012)
- ISSN：1530-6992
文摘
Conventional ordered phases such as crystals and liquid crystals have constant domain spacings. In this Letter, we report on the formation of coherently ordered morphologies wherein the domain spacing changes continuously along a specified direction. We have coined the term 鈥済radient crystal鈥?to refer to this structure, a signature of which is a small-angle X-ray scattering pattern that resembles a sundial. Gradient crystals composed of a gyroid morphology form spontaneously when ionic current is driven through a block copolymer electrolyte. We propose that this structure forms because it allows for a continuous change in domain spacing without requiring the introduction of defects. Previous studies have shown that applied electric fields ranging from 1000 to 40鈥?00 V/mm can induce long-range structural order, alignment, and morphological transitions in block copolymers. Gradient crystals form under applied electric fields as low as 2.5 V/mm due to the presence of direct ionic currents that are absent in the aforementioned studies.