Self-Assembly of Conjugated Polymers Into Ring Structures by Breath Figures

A simple method to fabricate rings of conjugated polymers is presented based on the breath figure technique. In humid atmosphere, the rapid evaporation of solvent induces the cooling of the solution surface of conjugated polymers. Water droplets condense onto the solution surface and undergo coalescence to form larger ones. After the solvent and water droplets evaporate completely, isolated rings are formed. Our results show that it is a general method to produce ring structure in different conjugated polymer systems. The influences of solvent properties, solution concentrations, etc. on the pattern formation are investigated. Compared with the conventional honeycomb structure obtained by breath figures, the key to the formation of ring structure is discussed. Furthermore, ring structure can be tuned from circular to elliptic by applying moist air flow with controlled direction onto the surface of the polymer solution. This approach offers a complimentary way to pattern conjugated polymers in a simple, cost-effective, and one-step matter.