May 6, 2010
Patterning and alignment of π-conjugated polymer
Long flexible nanowires of poly(3-hexylthiophene) can be deposited at desired locations and with a particular orientation by simply dip coating a chemically patterned substrate with aged solutions. The Han group based at Changchun Institute of Applied Chemistry, China, is studying the influence of the aggregation state of π-conjugated polymer in solution on film structure and device efficiency.
Dip coating, which provides many degrees of freedom – for example, withdrawing motion, solution properties, evaporation conditions and suspension chemistry – to control the deposition process, has been used to pattern the π-conjugated polymers. The combination of aged solution, chemically patterned substrate and dip-coating process has made it possible to deposit poly(3-hexylthiophene) (P3HT) and orientate the nanowires at desired locations.
It is widely accepted that on a chemically patterned substrate the solution-substrate interactions guide the solvent to the desired locations. Different wettabilities on the substrate cause the liquid to flow out of the lyophobic areas and into the lyophilic areas. However, the team found that the difference in the receding contact angles of the toluene solution rather than the toluene-substrate interaction determines the distribution of P3HT solution on the n-octadecyltrichlorosilane (OTS) patterned Si/SiOx substrate during the dip-coating process.
In combination with this thickness fluctuation of the thin liquid film, the size of P3HT aggregates in the solution, which changes during the ageing process, also determines the local structures in the two areas.
The researchers presented their work in the journal Nanotechnology.
About the author
Dr Longjian Xue studied the influence of interfacial properties on the polymer thin films at the State Key Lab of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry (CIAC), Chinese Academy of Sciences, China. He is now a postdoctoral researcher investigating the formation of nanostructures in an electric field at RWTH-Aachen University, Germany. Prof. Yanchun Han is director of the State Key Laboratory of Polymer Physics and Chemistry at CIAC. Her research interests include organic optoelectronic devices, polymer films, surfaces and interfaces, and nanostructured composite materials.