Synthesis and characterization of high χ block copolymers with new monomer DVBAM

Abstract

The directed self-assembly (DSA) of block copolymers (BCPs) is one of the most promising methods for nanofabrication technique with a sub-20 nm patterns. In DSA technique, the Flory-Huggins interaction parameter (χ), which is associated with repulsion between block chains, affects a defect density and correlation length of self-assembly nanopatterns. Therefore, BCPs with large χ value are important to form long-range ordered and well-defined nanostructures. In this study, we synthesized new benzamide monomer, N-dodecyl-4-vinylbenzamide (DVBAM), and its diblock copolymers composed of a crystalline hard poly(DVBAM) (PDVBAM) block and an amorphous and soft poly(methyl methacrylate) (PMMA) block. The resulting diblock copolymers were successfully synthesized with low polydispersity, ¯(M_w )/¯(M_n )<1.3, using a reversible addition-fragmentation chain transfer (RAFT) polymerization. The block copolymerization proceeded on controlled/living characteristics. The dependence of self-assembled morphologies was examined by controlling the molecular weight of diblock copolymers and the composition of PMMA block to PDVBAM segment. The morphologies of thin films of the block copolymers after solvent annealing were analyzed by atomic force microscopy (AFM), scanning electron microscope (SEM) and grazing-incidence small angle X-ray scattering (GISAXS). The results showed that new block copolymer thin film generates self-assembled nanopatterns (lamellaes or spherical domains) with large correlation length because of their large χ value.