Template-Directed Synthesis of One-Monomer-Thick Two-Dimensional Polymers Made of Cucurbit[6]uril

Abstract

Synthesis of two-dimensional (2D) polymers on surface is an attractive strategy for the fabrication of nanoscale devices. Although numerous approaches have been reported over the last several decades, the synthesis of one-monomer-thick, covalently bonded 2D polymers with a long-range-ordered internal structure has yet to be achieved. This thesis describes the synthesis and characterization of one-monomer-thick 2D polymers made of cucurbit[n]uril (CB[n]), a family of synthetic molecules comprising n glycoluril units. The CB[n] based 2D polymers were synthesized on an atomically flat template-stripped gold (TSG) surface via the cross metathesis of (allyloxy)12cucurbit[6]uril (AOCB[6]) which consists of a rigid disk-shaped host molecule with twelve polymerizable allyl groups at the periphery. To synthesize one-monomer-thick 2D polymers, well-ordered an ammonium-terminated self-assembled monolayer (SAM) was prepared on a TSG substrate. An adlayer of AOCB[6] formed through hydrogen bonding and charge-dipole interaction between the carbonyl portal of AOCB[6] and the terminal ammonium group on the SAM. Polymerization of the AOCB[6] adlyaer was carried out using the Grubbs’ catalyst and the resulting polymers were transferred to other substrates and characterized using various techniques including fluorescence spectroscopy and transmission electron microscopy, atomic force microscopy, and scanning tunneling microscopy. Interestingly, this 2D polymer shows a sheet-like structure and one-monomer-thick with several micrometer lateral dimensions. CB[n] has a hydrophobic hollow cavity that is accessible through two identical carbonyl portals and thus through strong host-guest interactions such 2D polymers become more attractive for various applications such as functionalized membrane, sensor, and others.