Conjugated, conductive polymers are the key component in the development of flexible displays, low-cost, large-scale displays, and thin-film transistors. [1] However, ever since the seminal discovery of the conductive nature of ("doped") polyacetylene by Heeger, McDiarmid, Shirakawa, and coworkers, the processing of conductive polymers into devices has been a critical issue. [2][3][4][5][6][7] The rigid conjugated polymer backbone results in very low solubilities in organic solvents and thermal properties that prohibit thermoplastic processing. These drawbacks can be overcome to some extent by introducing substituents as side chains, which, however, also alters the electronic properties and often requires additional synthetic effort. [1] Polyacetylene itself is still considered unprocessable. [4][5][6][7][8] Grafting to other polymers has been reported to result in processable materials. [9][10][11] We report a different approach, namely, the synthesis of aqueous dispersions of submicron polyacetylene particles by catalytic polymerization in emulsion. Such dispersions are suited for processing by printing techniques, as exemplified by the generation of a polyacetylene-based functioning electronic circuit by ink-jet printing as a straightforward and versatile technique.
The concept of processing polyacetylene from polymer particle dispersions was suggested early on, but hitherto has not been reported. [12,13,38] The few examples of polyacetylene particle dispersions reported to date are restricted to dispersions of polyacetylene in organic solvents. [12,14,15] The reported catalyst productivities are very low (35 mol acetylene per mol metal), [15] such that metal residues can be problematic for polymer stability and also for the electronic properties. It is well known that polymer particles can be stabilized in aqueous dispersions effectively by appropriate surfactants. Printing techniques are usually developed for aqueous systems. The insolubility of most polymers in water can be advantageous in the preparation of multilayer devices, in which the application of organic solvents often poses