Abstract
Silicon-containing block copolymer 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. The rod–coil block copolymer with the volume fraction of the Si-containing block of 0.22 presents an asymmetrical lamellar structure in which the rod block forms a hexatic columnar nematic liquid crystalline phase. A solvent vapor annealing step first produces well-ordered in-plane cylinders of the Si-containing block, then a subsequent thermal annealing 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 and wide-angle X-ray scattering.
Highlights
Silicon-containing block copolymer 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
The conformationally asymmetrical PDMS-b-PMPCS (DM, Figure 1a) block copolymer has a high χ value estimated as about 4 times that of the well-studied high-χ block copolymers (BCPs) PDMS-b-PS.[12,35]
The phase behavior of the thermotropic liquid crystalline PMCPS is highly dependent on its molecular weight (MW) and the thermal annealing temperature
Summary
Silicon-containing block copolymer 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. A subsequent thermal anneal of the in-plane cylindrical morphology resulted in vertical lamellae with hexagonal columnar nematic liquid crystalline ordering of the rod block parallel to the substrates.
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