Highly Asymmetric Lamellar Nanopatterns via Block Copolymer Blends Capable of Hydrogen Bonding

Abstract

Highly asymmetric lamellar microdomains, such as those required for many lithographic line patterns, cannot be straightforwardly achieved by conventional block copolymer self-assembly. We present a conceptually new and versatile approach to produce highly asymmetric lamellar morphologies by the use of binary blends of block copolymers whose components are capable of hydrogen bonding. We first demonstrate our strategy in bulk systems and complement the experimental results observed by transmission electron microscopy and small-angle X-ray scattering with theoretical calculations based on strong stretching theory to suggest the generality of the strategy. To illustrate the impact on potential lithographic applications, we demonstrate that our strategy can be transferred to thin film morphologies. For this purpose, we used solvent vapor annealing to prepare thin films with vertically oriented asymmetric lamellar patterns that preserve the bulk morphological characteristics. Due to the highly asymmetric lamellar microdomains, the line width is reduced to sub-10 nm scale, while its periodicity is precisely tuned.

Effect of the Degree of Hydrogen Bonding on Asymmetric Lamellar Microdomains in Binary Block Copolymer Blends

“…Since the volume fraction of PS microdomain in the blend was 0.8, the ratio of PS and (P2VP + PHS) lamellar width is 4, confirmed by smallangle X-ray scattering (SAXS) and transmission electron microscopy (TEM). 20,21 Very recently, Shi et al 22,23 reported that an extremely asymmetric lamellar structure with up to ∼97 wt % of one block by using binary mixture of a miktoarm star block copolymer [S(IS′) 3 , here S and I denote PS and polyisoprene, respectively] and suitable choice of molecular weight of PS homopolymer. Although S(IS′) 3 stabilized extremely asymmetric lamellar structure even at large amount of PS homopolymer, the resulting microdomains do not show longrange ordering, resulting in nonuniform lamellar spacing throughout the entire area.…”

“…20 Since asymmetric lamellar microdomains are formed due to the interface curvature change by favorable hydrogen bonding interaction between the hydroxyl group and nitrogen atom, a large ratio of lamellar width (thus, enhanced asymmetry) could potentially be achieved by increasing the degree of the hydrogen bonding. Poly(4-vinylpyridine) (P4VP) is a model polymer that exhibits much stronger hydrogen bonding with PHS compared with P2VP.…”

Phase Behavior of Binary Blend Consisting of Asymmetric Polystyrene-block-poly(2-vinylpyridine) Copolymer and Asymmetric Deuterated Polystyrene-block-poly(4-hydroxystyrene) Copolymer

“…We also demonstrated the potential of lithographic applications that the line width can be reduced to the sub-10 nm scale and its periodicity can be precisely tuned by fabricating a thin film having vertically oriented asymmetric lamellar microdomains. 25 We consider possible morphologies of a binary blend of high molecular weight of as-PS-b-P2VP and lower molecular weight of as-PS-b-PHS based on the conjecture. The first one is that as-PS-b-PHS chains are located in either PS microdomains or P2VP microdomains of as-PS-b-P2VP (Figure 1a−c).…”

Controllable multicompartment morphologies from cooperative self-assembly of copolymer–copolymer blends

“…Such structures can also be obtained from the cooperative self-assembly of block copolymer blends, such as AB/B [23][24][25][26] , AB/AC [27][28][29][30] , AB/CB 12,[31][32][33][34][35][36][37] and AB/BAB 38,39 . Such structures are the focus of the study here.…”