Block copolymers (BCPs) are widely used in materials science due to their unique ability to self-assemble into various nanostructures, which is well described by the segregation strength cN. Recent advanced in BCPs have focused on the development of new systems that can overcome the size limitation of traditional BCPs. Such efforts have been demonstrated with design and synthesis of new type of BCPs, changing the BCP architectures, or introducing the specific junctions between blocks. In this work, we demonstrate that the introduction of short middle block can manipulate the effective c between A and B blocks. For example, in the polystyrene (PS) and polymethyl methacrylate (PMMA) based BCPs, the short middle block of PS-r-PMMA (R) was incorporated to prepare the ARB type triBCPs. In this case, the order-disorder transition (ODT) temperatures decreased due to the reduced effective c. Moreover, it was also expected that the R block increases effective dispersity via compositional distribution, leading to an increased domain size compared to the AB diBCP with same MW and dispersity. We prepared various ARB type triBCPs and AB diBCPs having the similar dispersity via living-radical polymerization, and their morphologies were characterized by TEM, SAXS, and GISAXS. Consequently, it was shown that the ARB-type triBCP exhibited ~50 % increase in the domain spacing compared to the AB diBCPs with same MW and dispersity. As another example, we synthesized AHB-type triBCP, where A and B represent the PS and PMMA blocks, and H represents a short poly(methacrylic acid) (PMAA) that can form hydrogen bonds with the same PMAA (H block) or with PMMA (B block). Due to the hydrogen bonding, we hypothesized the enhanced intermolecular interactions at the domain interface will increase the effective χ, thereby increasing the ODT as compared with AB diblock with the same molecular weight, in contrast with ARB case. This enhanced window for the ordered structure allowed us to fabricate sub-10 nm nanostructures. AHB-type triBCP was synthesized through the sequential anionic polymerization of styrene, tert-butyl methacrylate (tBMA), and MMA. Subsequently, the PtBMA block was modified to PMAA via acid deprotection. The resulting BCP was thermally annealed in bulk and thin film, and characterized by SEM, TEM, and GISAXS. The results in both systems, ARB and AHB type triBCPs, were also compared with theoretical predictions.

Manipulation of effective interaction parameters from ARB and AHB type triblock copolymers

253rd National Meeting (2017)

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