Self-Alignment of Cylinder-Forming Silicon-Containing Block Copolymer Films

Abstract

Well-ordered perpendicular cylinders of star-block copolymers (BCPs) composed of polystyrene and poly­(dimethyl­siloxane) blocks with high aspect ratio can be achieved by using a combination of architecture effect (entropy effect) and surface air plasma treatment (enthalpy effect). An interesting morphological evolution from disordered texture to hexagonally packed cylinders with perpendicular orientation has been observed, in which perpendicular cylinders are initiated at the top surface and bottom substrate of the thin film, followed by a self-alignment process, resulting in span-thru cylinders through the thin film. The self-alignment process is systematically examined by a combination of real space imaging using transmission electron microscopy, reciprocal space imaging using grazing incidence small-angle X-ray scattering, and three-dimensional tomography. The experimental results reveal a unique mechanism for the formation of highly ordered BCP thin films via surface-induced nucleation of perpendicularly oriented cylinders followed by lateral ordering of the cylinders. This discovery provides an insight into the mechanisms of confined self-assembly of BCP for the engineering of nanostructured thin films with controlled orientation and long-range order.

Vacuum-Driven Orientation of Nanostructured Diblock Copolymer Thin Films

“…Accordingly, it is feasible to fabricate welloriented film-spanning perpendicular cylinders due to the nucleation and growth during microphase separation from the top and bottom of the thin film simultaneously through a selfalignment process. 36 Yet, as shown in Figure 5a of the TEM micrograph, randomly distributed dotlike textures with deformed features could be found after thermal annealing at 300 °C under a high vacuum degree. The formation of a hexagonally packed dotty pattern mixed with a smeared texture reflects the misalignment problem of the cylinder microdomains, even though the formation of the perpendicular cylinders is indeed driven by vacuum from the top and the bottom of the thin film.…”

“…Similar results for the vacuum-driven orientation from the top and the bottom of the thin film can be found as discussed previously (see Figure S7 for details). Accordingly, it is feasible to fabricate well-oriented film-spanning perpendicular cylinders due to the nucleation and growth during microphase separation from the top and bottom of the thin film simultaneously through a self-alignment process . Yet, as shown in Figure a of the TEM micrograph, randomly distributed dotlike textures with deformed features could be found after thermal annealing at 300 °C under a high vacuum degree.…”

Synthesis, Molecular Characterization, and Phase Behavior of Miktoarm Star Copolymers of the ABn and AnB (n = 2 or 3) Sequences, Where A Is Polystyrene and B Is Poly(dimethylsiloxane)

“…The utilization of PDMS-based copolymers on numerous applications, ranging from nanotechnology to photonics constitutes a highly investigated topic, due to the advanced properties that these materials exhibit. − Also, unique structures may occur due to the high immiscibility of PDMS toward other blocks. PDMS-based BCPs (block copolymers) either linear or graft, miktoarm, and/or star block copolymers ,, are of high scientific and technological interest, , and several applications employing the aforementioned systems have already been reported.…”

Lyotropic Morphology Transition of Double Zwitterionic Diblock Copolymer Aqueous Solutions

“…Block copolymers produce periodic ordered nanostructures including body‐centered cubic, hexagonally close‐packed cylinder (HEX), bicontinuous cubic gyroid, and lamellar (LAM) due to immiscibility in the dissimilar chains, [ 1–5 ] and are fascinating as unique materials based on the prescribed nanostructures. [ 6–8 ] Introduction of solvents into block copolymers expands the diversity of morphologies and gives the capability to transform in response to chemical and physical conditions because of the variable interactions between the solvents and polymer chains. [ 9–14 ] Neutral or weakly selective solvents distribute evenly in both phases, thereby the morphology is steady although reducing the interfacial energy.…”