The effect of molecular weight on the rate and extent of melt-infiltration of polystyrene into mesoporous silicon-based photonic crystals is investigated as a function of polymer molecular weight. Polymer viscosity and chain end-to-end (Ree) distance correlate with the rate and extent of infiltration. High molecular weight (Mw) polystyrene (200 or 400 kDa) infiltrates the mesoporous material in two distinct phases: a rapid phase where the larger pores of the template are filled, followed by a slower phase during which the smaller pores fill. Low molecular weight polystyrene (20 and 35 kDa) fills the pores more uniformly, progressing into the film as a single, relatively distinct front of liquid polymer. Scanning electron microscope (SEM) analyses of cross sections of the films are consistent with the optical measurements, showing a lower extent of infiltration for the higher molecular weight polymers. Removal of the porous Si templates by soaking in a chemical etchant generates free-standing films of nanostructured polymer. The low molecular weight samples display better replication. Partial removal of the template enables tuning of the hydrophobicity of the free-standing polymer films, which is demonstrated with a flexible and chemically stable polyvinylidene fluoride polymer.

Engineering the Properties of Polymer Photonic Crystals with Mesoporous Silicon Templates

BARILLARO, GIUSEPPE;
2017

Abstract

The effect of molecular weight on the rate and extent of melt-infiltration of polystyrene into mesoporous silicon-based photonic crystals is investigated as a function of polymer molecular weight. Polymer viscosity and chain end-to-end (Ree) distance correlate with the rate and extent of infiltration. High molecular weight (Mw) polystyrene (200 or 400 kDa) infiltrates the mesoporous material in two distinct phases: a rapid phase where the larger pores of the template are filled, followed by a slower phase during which the smaller pores fill. Low molecular weight polystyrene (20 and 35 kDa) fills the pores more uniformly, progressing into the film as a single, relatively distinct front of liquid polymer. Scanning electron microscope (SEM) analyses of cross sections of the films are consistent with the optical measurements, showing a lower extent of infiltration for the higher molecular weight polymers. Removal of the porous Si templates by soaking in a chemical etchant generates free-standing films of nanostructured polymer. The low molecular weight samples display better replication. Partial removal of the template enables tuning of the hydrophobicity of the free-standing polymer films, which is demonstrated with a flexible and chemically stable polyvinylidene fluoride polymer.
Wang, Joanna; Lee, Gha Y.; Kennard, Rhiannon; Barillaro, Giuseppe; Bisiewicz, Rachel H.; Cortez Lemus, Norma A.; Cao, Xiaoyu C.; Anglin, Emily J.; Park, Jennifer S.; Potocny, Andrea; Bernhard, Drew; Li, Jianlin; Sailor, Michael J.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/855481
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