Ribet Stephanie M, Murthy Akshay A, Roth Eric W, Dos Reis Roberto, Dravid Vinayak P
Department of Materials Science and Engineering, Northwestern University, Evanston, IL.
International Institute of Nanotechnology, Northwestern University, Evanston, IL.
Mater Today (Kidlington). 2021 Nov;50:100-115. doi: 10.1016/j.mattod.2021.05.006. Epub 2021 Jun 19.
Inspired by the unique architectures composed of hard and soft materials in natural and biological systems, synthetic hybrid structures and associated soft-hard interfaces have recently evoked significant interest. Soft matter is typically dominated by fluctuations even at room temperature, while hard matter (which often serves as the substrate or anchor for the soft component) is governed by rigid mechanical behavior. This dichotomy offers considerable opportunities to leverage the disparate properties offered by these components across a wide spectrum spanning from basic science to engineering insights with significant technological overtones. Such hybrid structures, which include polymer nanocomposites, DNA functionalized nanoparticle superlattices and metal organic frameworks to name a few, have delivered promising insights into the areas of catalysis, environmental remediation, optoelectronics, medicine, and beyond. The interfacial structure between these hard and soft phases exists across a variety of length scales and often strongly influence the functionality of hybrid systems. While scanning/transmission electron microscopy (S/TEM) has proven to be a valuable tool for acquiring intricate molecular and nanoscale details of these interfaces, the unusual nature of hybrid composites presents a suite of challenges that make assessing or establishing the classical structure-property relationships especially difficult. These include challenges associated with preparing electron-transparent samples and obtaining sufficient contrast to resolve the interface between dissimilar materials given the dose sensitivity of soft materials. We discuss each of these challenges and supplement a review of recent developments in the field with additional experimental investigations and simulations to present solutions for attaining a nano or atomic-level understanding of these interfaces. These solutions present a host of opportunities for investigating and understanding the role interfaces play in this unique class of functional materials.
受自然和生物系统中由硬材料和软材料组成的独特结构启发，合成混合结构及相关的软硬界面最近引起了广泛关注。即使在室温下，软物质通常也受涨落主导，而硬物质（通常作为软组分的基底或锚定物）则由刚性力学行为支配。这种二分法提供了大量机会，可在从基础科学到具有重大技术意义的工程见解的广泛领域中利用这些组分所具有的不同特性。这类混合结构，包括聚合物纳米复合材料、DNA功能化纳米粒子超晶格和金属有机框架等，在催化、环境修复、光电子学、医学等领域带来了有前景的见解。这些硬相和软相之间的界面结构存在于各种长度尺度上，并且常常强烈影响混合系统的功能。虽然扫描/透射电子显微镜（S/TEM）已被证明是获取这些界面复杂分子和纳米级细节的宝贵工具，但混合复合材料的特殊性质带来了一系列挑战，使得评估或建立经典的结构-性能关系尤其困难。这些挑战包括与制备电子透明样品相关的挑战，以及鉴于软材料对剂量的敏感性，在获得足够对比度以分辨不同材料之间的界面方面的挑战。我们讨论了这些挑战中的每一个，并通过额外的实验研究和模拟补充了该领域的最新进展综述，以提出实现对这些界面的纳米或原子级理解的解决方案。这些解决方案为研究和理解界面在这类独特功能材料中所起的作用提供了大量机会。
