Phase structural formation and oscillation in polystyrene-block-polydimethylsiloxane thin films

Abstract

The solvent-induced spherical structure in a polystyrene-block-polydimethylsiloxane (PS-b-PDMS) block copolymer was obtained and stabilized by preparing both the bulk and thin films from propylene glycol methyl ether acetate (PGMEA) solutions. The diblock copolymer possessed a total molecular weight of 42 kDa with a PS volume fraction of 72.2%, and it formed a cylindrical phase structure in the equilibrium bulk state. During thermal annealing, only changes in the sphere size and packing rearrangement were found. In contrast, a unique structure evolution route was observed during solvent treatments. Under a controlled vapour of a PS selective solvent, an oscillation of the structural transition between spheres and cylinders was observed in the thin films. The kinetics of this oscillation of structural transition was found to be closely related to the solvent vapour concentration and film thickness. This experiment revealed a unique ordering pathway towards the equilibrium structure in the thin film for this strongly segregated PS-b-PDMS diblock copolymer.

Photoluminescent Arrays of Nanopatterned Monolayer MoS2

“…A SEM image of such domains (Figure e) exhibits both nanodots and nanorods of monolayer MoS 2 , and the measured dimensions of the nanopatterns in Figure f,g are consistent with those of the ox‐PDMS structures in Figure . The uniform domains as in Figure c are composed primarily of rod‐shaped structures with a small number of nanodots interspersed as revealed by SEM (Figure h), similar to previously reported patterns formed with a PS‐ b ‐PDMS polymer . The ratio of areas covered by dots and rods is determined by the thickness of the deposited BCP and affects the optical contrast of the nanostructured domains.…”

Block Co-Polymers for Nanolithography: Rapid Microwave Annealing for Pattern Formation on Substrates

“…This coherence is a significant advantage for application of these films (particularly for subsequent pattern transfer to underlying silicon substrate that would be needed in industry). It should also be noted that the good wetting of the substrate might be related to the efficient heating of the sample and short treatment periods that limit solvent condensation [23]. It should be emphasized that the regularity and structural order of the patterns indicate that the surface interactions between the BCP and the brush coated surface are significantly robust to survive the microwave processing and, in particular, thermal and mechanical strains that must exist at the interfaces.…”

“…The oxidation of the PDMS cylinders during this etch step is confirmed by FTIR with the detection of a Si-O-Si signal at 1100 cm −1 [22] as displayed in Figure 1c. De-wetting is a major issue with high χ BCP systems such as PS-b-PDMS and this can lead to the formation of BCP island structures at the substrate surface upon solvent annealing this polymer for extended times [23]. However, it should be noted that the 1.0 wt% BCP in toluene solution used in film casting provided a continuous film (film thickness, ~34 nm (Table 2)), i.e., close to the 33 nm BCP domain spacing) and de-wetting was not observed after microwave irradiation.…”

Three‐Dimensional Block Copolymer Nanostructures by the Solvent‐Annealing‐Induced Wetting in Anodic Aluminum Oxide Templates

“…Different from the melt method, the Flory–Huggins interaction parameter ( χ ) between the two blocks is also affected by the solvent during the annealing process . The volume fractions of the two blocks are also changed due to the different degree of swelling of polymer chains in the solvent vapors …”

“…[ 37 ] The volume fractions of the two blocks are also changed due to the different degree of swelling of polymer chains in the solvent vapors. [ 38 ] The block copolymer used in this work is polystyreneblock -polydimethylsiloxane (PS-b -PDMS). This polymer has been suggested as a promising candidate for nanolithography because it can self-assemble into microdomain patterns with large correlation lengths and low defect densities.…”