Synthesis of poly(styrene-b-4-(tert-butyldimethylsiloxy)styrene) block copolymers and characterization of their self-assembled patterns

Abstract

Directed self-assembly (DSA) of block copolymers (BCPs) is regarded as one of the alternative methods to traditional top-down lithography approaches due to its ability to form well-aligned nanostructures such as spheres, cylinders, and lamellae with controlled domain size. Despite extensive research activities in this field, the question of how the Flory-Huggins interaction parameter (chi) and polydispersity of chains affect self-assembled pattern formation remains. Here, we report the self-assembly behavior of poly(styrene-b-4-(tert-butyldimethylsiloxy) styrene) (PS-b-P4BDSS) BCP, which has an intermediate. between those of poly(styrene-b-methyl methacrylate) (PS-b-PMMA) and poly(styrene-b-dimethylsiloxane) (PS-b-PDMS), which allows pattern formation of the BCP in a wide range of length scales induced by simple thermal annealing. We also demonstrate the effect of polydispersity on self-assembled pattern quality by comparing BCPs synthesized via anionic polymerization with those synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization. The self-assembled pattern of BCPs with a narrow PDI (PDI < 1.05 via anionic polymerization) shows 38% lower line edge roughness than that of BCPs with a broad PDI (PDI > 1.15 via RAFT polymerization).