Exploring the Synthesis of Two-Dimensional Polymers: From Langmuir Films to Crystals
AuthorMurray, Daniel J.
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Since the isolation of graphene the field of two-dimensional (2D) materials has become an intense research topic. Much of this work deals with naturally occurring 2D materials such as graphene, hexagonal boronitride, and molybdenum disulfide. While these materials have many unique properties and promising applications their structures are essentially fixed. This is one reason that interest in 2D materials that are synthesized using mild synthetic organic chemistry methods is growing. Using mild organic chemistry methods will allow for 2D materials with structures that have been designed to suit a specific application. These structures can be tuned and optimized in the same way small molecules can be. There are many promising applications such as separations membranes, surface patterning, and molecular electronics that will benefit from the realization of these materials. In this dissertation I will explore the design principles, and methods for the synthesis of these materials, which we call two-dimensional polymers (2DPs). Chapter one will explore how we can classify 2DPs using the theory of tilings. Doing this not only provides a way to define 2DPs but also gives insights into the design of appropriate monomers for the synthesis of 2DPs. Four different 2DPs will be presented in this dissertation. The first two are synthesized using amphiphilic shape-persistent tri-functional monomers that are confined at the air/water interface. Figure Ia shows antrip-DEG, which is one of the amphiphilic monomers used. These monomers are spread at the air/water interface and irradiated to give the 2DP. High resolution scanning probe microscopy is used to show that both of the 2DPs made at the air/water interface are periodic and have pores ~0.9 nm in diameter. The last two 2DPs are made by a crystal approach. In this approach monomers are crystalized to preorganize them in 2D. The crystal is then irradiated with UV light to polymerize the 2D layers. Exfoliation of the layers provides the 2DP. We have characterized the crystals by X-ray diffraction, numerous spectroscopy techniques, and numerous microscopy techniques.