Revealing the 3D Structure of Block Copolymers with Electron Microscopy: Current Status and Future Directions

Abstract

Block copolymers (BCPs) are considered model systems for understanding and utilizing self-assembly in soft matter. Their tunable nanometric structure and composition enable comprehensive studies of self-assembly processes as well as make them relevant materials in diverse applications. A key step in developing and controlling BCP nanostructures is a full understanding of their three-dimensional (3D) structure and how this structure is affected by the BCP chemistry, confinement, boundary conditions, and the self-assembly evolution and dynamics. Electron microscopy (EM) is a leading method in BCP 3D characterization owing to its high resolution in imaging nanosized structures. Here we discuss the two main 3D EM methods: namely, transmission EM tomography and slice and view scanning EM tomography. We present each method’s principles, examine their strengths and weaknesses, and discuss ways researchers have devised to overcome some of the challenges in BCP 3D characterization with EM- from specimen preparation to imaging radiation-sensitive materials. Importantly, we review current and new cutting-edge EM methods such as direct electron detectors, energy dispersive X-ray spectroscopy of soft matter, high temporal rate imaging, and single-particle analysis that have great potential for expanding the BCP understanding through EM in the future.

The Development and Atomic Structure of Zinc Oxide Crystals Grown within Polymers from Vapor Phase Precursors

“…42 Demonstrated applications included improved water purification, 10,43 controlled mechanical 16,17,36,40,44−46 and electrical properties, 23,30,38,39,47 templating for nanofabrication, 11,18,48 and imaging contrast enhancement. 9,49,50 Mechanistic studies are imperative for an improved understanding of the SIS process and its better integration into real-world systems. Currently, the great majority of such studies were dedicated to trimethyl aluminum (TMA), 7,8,12,13,15,29 which has been probed by microgravimetry, infrared (IR) spectroscopy, ellipsometry, electron microscopy (EM), time-of-flight-secondary ion mass spectrometry (ToF-SIMS), X-ray, and other methods, with models developed to predict and understand diffusion and growth as a function of process parameters.…”

“…The scope of polymers has been greatly broadened over this time period, as well, and SIS has been used to alter the inherent properties of both natural , and synthetic polymers, ,− including block copolymers (BCPs) and block terpolymers . Demonstrated applications included improved water purification, , controlled mechanical ,,,,− and electrical properties, ,,,, templating for nanofabrication, ,, and imaging contrast enhancement. ,, …”

“… 42 Demonstrated applications included improved water purification, 10 , 43 controlled mechanical 16 , 17 , 36 , 40 , 44 − 46 and electrical properties, 23 , 30 , 38 , 39 , 47 templating for nanofabrication, 11 , 18 , 48 and imaging contrast enhancement. 9 , 49 , 50 …”

Hybrid Metrology for Nanostructured Optical Metasurfaces

“…Nonetheless, attaining such an advanced level of control over the refractive index requires surmounting numerous technological and metrological hurdles associated with fabricating and measuring dimensional aspects (e.g., size, height, and periodicity) − as well as structural features (e.g., chemical state and material density) of the meta-atoms (Figure c).…”