Department of Chemical Engineering, University of California, Berkeley, California 94720, USA.
Nano Lett. 2012 Jan 11;12(1):464-8. doi: 10.1021/nl203826s. Epub 2011 Dec 22.
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 "gradient crystal" 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 40,000 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.
传统的有序相，如晶体和液晶，具有恒定的畴间距。在这封信中，我们报告了相干有序形态的形成，其中畴间距沿着指定方向连续变化。我们创造了“梯度晶体”这个术语来指代这种结构，其特征是小角 X 射线散射图案类似于日晷。当离子电流通过嵌段共聚物电解质驱动时，由介晶形态组成的梯度晶体自发形成。我们提出这种结构形成的原因是它允许域间距连续变化，而不需要引入缺陷。先前的研究表明，施加的电场范围从 1000 到 40000 V/mm 可以诱导嵌段共聚物的长程结构有序、排列和形态转变。由于存在直接的离子电流，梯度晶体在低至 2.5 V/mm 的外加电场下形成，而在上述研究中则不存在这种电流。
