Shape-Directed Patterning and Surface Reaction of Tetra-diacetylene Monolayers: Formation of Linear and Two-Dimensional Grid Polydiacetylene Alternating Copolymers

Side chains containing two diacetylene units spaced by an odd number of methylene units exhibit pronounced bumps composed of 0.3 nm steps, in opposite directions, at odd and even side-chain positions. In densely packed self-assembled monolayers, the bis-diacetylene bumps stack into each other, similar to the stacking of paper cups. Bis-diacetylene side chain structure and associated packing constraints can be tailored by altering the bump width, direction, side-chain location, and overall side-chain length as a means to direct the identities and alignments of adjacent molecules within monolayers. Scanning tunneling microscopy (STM) at the solution-HOPG interface confirms the high selectivity and fidelity with which bis-diacetylene bump stacking directs the packing of shape-complementary side chains within one-component monolayers and within two-component, 1-D self-patterned monolayers. Drop cast or moderately annealed monolayers of anthracenes bearing two bis-diacetylene side chains assemble single domains as large as 10(5) nm(2). Light-induced cross-linking of two-component, 1-D patterned monolayers generates linear polydiacetylene alternating copolymers (A-B-)(x) and 2-D grid polydiacetylene alternating copolymers (A(-B-)(-B-)A(-B-)(-B-))(x) that covalently lock in monolayer structure and patterns.