Vertical Lamellae Formed by Two-Step Annealing of a Rod-Coil Liquid Crystalline Block Copolymer Thin Film.
ACS nano(2020)
摘要
Silicon-containing block copolymer (Si-BCPs) thin films with high interaction parameter and etch contrast are ideal candidates to generate robust nanotemplates for advanced nanofabrication, but they typically form in-plane oriented microdomains as a result of the dissimilar surface energies of the blocks. Here, we describe a two-step annealing method to produce vertically aligned lamellar structures in thin film of a silicon-containing rod-coil thermotropic liquid crystalline block copolymer (LC BCP). The rod-coil BCP with volume fraction ~0.22 of the Si-containing block presents an asymmetrical lamellar structure in which the rod block forms a hexatic columnar nematic liquid crystalline phase. A solvent vapor annealing (SVA) step first produces well-ordered in-plane cylinders, then a subsequent thermal annealing (TA) promotes the phase transition from in-plane cylinders to vertical lamellae. The pathways of the order-order transition were examined by microscopy and in situ using grazing incidence small angle X-ray scattering (GISAXS) and wide angle X-ray scattering (GIWAXS).
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关键词
silicon-containing block copolymer,liquid crystal block copolymer,thin film,solvent vapor annealing thermal annealing,vertical orientation
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