Interplay of viscosities in controlling the orientation of conjugated polymer thin films fabricated by floating film transfer method

Aligned thin films with controlled molecular orientation are highly desired for high performance organic electronic devices. A crystalline conjugated copolymer DPP- TTT has been utilized to prepare large area and oriented thin films by the floating film transfer method (FTM). Amongst the various factors controlling the orientation under FTM, relative viscosities of polymer solution and orthogonal liquid substrates have been demonstrated to playa pivotal role not only in controlling the magnitude but also the directionality of the molecular orientation. It was revealed that utilization of the polymer solution and orthogonal liquid substrates with varying viscosities exhibited a reversal of orientation direction, when the viscosity of the polymer solution was higher than that of the orthogonal liquid substrate.