High χ–Low N Block Polymers: How Far Can We Go?

Block polymers incorporating highly incompatible segments are termed "high χ" polymers, where χ is the Flory-Huggins interaction parameter. These materials have attracted a great deal of interest because low molar mass versions allow for the formation of microphase-separated domains with very small (<10 nm) feature sizes useful for nanopatterning at these extreme dimensions. Given that well-established photolithographic techniques now face difficult challenges of implementation at scales of 10 nm and below, the drive to further develop high χ block polymers is motivated by trends in the microelectronics industry. This Viewpoint highlights our perspective on this niche of block polymer self-assembly. We first briefly review the relevant recent literature, exploring the various block polymer compositions that have been specifically designed for small feature size patterning. We then overview the now standard method for the benchmarking χ values between different pairs of polymers and the consequences of low N and high χ on the thermodynamic aspects of microphase separation. Finally, we comment on restrictions going forward and offer our perspective on the future of this exciting area of block polymer self-assembly.