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Channel flow setup. The desired mesoscopic pattern is carved through a thick polytetrafluoroethylene (PTFE) sheet; this sheet is then sandwiched between a top aluminum plate, and a bottom silicon wafer covered with a spin-coated block copolymer film, to form the channel. The syringe pump (right) drives fluid (oil) into the channel through a hole in the top plate; fluid exits at the edge of the PTFE sheet. The assembly is clamped to a digital hot plate to heat the polymer film above the glass transition temperature of the polystyrene block.
PS-PHMA 21-64 diblock copolymer alignment in a complex channel. The channel is wide and from inlet to outlet. Each TM-AFM micrograph was taken at the center of the channel, at the indicated location, showing how well the cylinders ( spacing) align with the flow direction.
PS-PEP 5-13 diblock copolymer alignment in the same complex channel as in Fig. 2. Each wide TM-AFM micrograph was taken at the center of the channel, at the indicated location, showing how well the cylinders ( spacing) align with the flow direction. No images are shown from the upstream portion of the channel due to extensive delamination of the film at high stresses.
Alignment of PS-PHMA 21-64 in a diverging-converging wedge channel (left), which includes a preheating chamber for the fluid. The graph shows the nematic order parameter as a function of stress, after of flow at ; diamonds are from the diverging portion of the channel, whereas triangles are from the converging portion. Crosses are data generated on the same polymer from rheometer experiments (, ) for comparison. The continuous curves are fitted to the recrystallization model, with either (bold line) or (thin line).
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