Tailored and Guided Dewetting of Block Copolymer/Homopolymer Blends

Abstract

The dewetting and ordering characteristics of a lamellae forming poly(styrene-block-methyl methacrylate) (PS-b-PMMA) block copolymer (BCP) either alone or blended with low molecular weight polystyrene (PS) and polymethylmethacrylate (PMMA) homopolymers were investigated. Although a significant reduction of the morphological stability is observed for the blend BCP compared to the neat BCP, an increase of one order of magnitude occurs in the correlation length of the lamellar nano-domains.Moreover, the morphological instability of blend BCP results in dewetting of relatively thick films with the formation of micrometric size areas consisting of highly ordered and defect free perpendicular lamellae monodomains. These results can be exploited for large-scale manufacturing of BCP-based plasmonic and optical structures featuring substantial thickness-modulation.

Hyperbolic Metamaterials via Hierarchical Block Copolymer Nanostructures

“…As reported in our previous work, [ 36 ] the dewetting process determined by BCP/homopolymer blend instability generates highly ordered lamellar nanofeatures perpendicularly oriented to the substrate in a single‐grain configuration, representing a promising method for fabricating large‐scale templates for metamaterials with in‐plane optical axis. However, its practical implementation is prevented by the random disposition of the dewetted droplets over unpatterned surfaces.…”

“…As a result, a low‐temperature dewetting process, typically occurring in ultrathin (sub‐10 nm) films, [ 46 ] takes place on relatively thick BCPs. [ 36 ]…”

“…Substrate neutralization was performed by grafting process of α‐hydroxy ω‐Br polystyrene‐ stat ‐polymethyl methacrylate (PS‐ stat ‐PMMA) random copolymer (RCP) (14.60 kg mol –1 ), with styrene fraction ( f ) of 0.59 and a polydispersity index Đ = 1.30, [ 36 ] over silicon wafers covered by 1.5 nm thick native oxide layer. A solution of PS‐ stat ‐PMMA (18 mg) in toluene (2 mL) was spin‐coated onto the Si wafers at 3000 rpm for 60 s [ 59 ] after cleaning and substrate activation by O 2 plasma treatment at 130 W for 10 min.…”

“…Low molecular weight homopolymer PMMA (3.9 kg mol –1 ) with Ð = 1.18 and PS (3.1 kg mol –1 ) with Ð = 1.09 were synthesized as described in a previous work. [ 36 ] A solution prepared with equal amounts of PS and PMMA homopolymers (1.12 mg) blended with BCP (4.5 mg) and dissolved in toluene (2 mL) was spin‐coated over RCP‐neutralized substrate obtaining a 35 nm thick layer. Subsequent annealing treatment by RTP at 270 °C for 600 s in N 2 environment induced the dewetting in the BCP blend film.…”

“…The SEM micrographs were processed to evaluate the long‐range ordering and orientation of the lamellar nanostructures by using a standard software routine; further details can be found in ref. [ 36 ] . 3D optical profilometer (S neox SENSOFAR) equipped with a 150× confocal objective was used for the determination of the droplet heights.…”