Block Copolymer Bottlebrushes: New Routes to Ever Smaller Microdomain Sizes

Block copolymer self-assembly presents exciting opportunities for the development of nanotemplates for advanced lithography applications, wherein the microdomain sizes (\textasciitilde 10--100 nm) are governed by the total copolymer degree of polymerization, $N$. However, this methodology is limited in its smallest achievable length scale, since AB diblock copolymers self--assemble only above a critical $N$ that depends on the magnitude of the effective segmental interaction parameter $\chi_{\mathrm{AB}}$. Numerous recent reports have focused on developing ``high $\chi_{\mathrm{AB}}$'' AB diblocks that self--assemble at low values of $N$. In this talk we explore the ability of non-linear polymer architectures to induce block copolymer ordering at reduced length scales. Thus, we describe the melt and thin-film self-assembly behavior of block copolymer bottlebrushes derived from linking the block junctions of low molecular weight AB diblocks. We quantitatively demonstrate that increasing the bottlebrush backbone degree of polymerization ($N_{\mathrm{backbone}})$ results in a larger reduction in the critical copolymer arm degree of polymerization ($N_{\mathrm{arm}})$ required for self-assembly, thus reducing the length scales at which these materials self-assemble.