Impact of stereocomplexation on the directed self-assembly poly (styrene-$b$-\textit{(rac)}-lactide) on chemically patterned surfaces

Poly (styrene) - block -- poly (\textit{rac}- lactide) (PS-\textit{b(rac)}PLA) with bulk lamellar period, L$_{\mathrm{o}}$, was directed to assemble on chemically patterned surfaces with period , L$_{\mathrm{s}}$. The surface energies of the blocks are similar enabling thermal annealing of the films. The racemic PLA block including short sequences of L- and D-lactide acid chains formed stereocomplexes. PS-\textit{b(rac)}PLA could be directed to assemble with a high degree of perfection over the entire range of 1 \textless L$_{\mathrm{s}}$/L$_{\mathrm{o}}$ \textless 2. As the L$_{\mathrm{o}}$ increased to accommodate the larger L$_{\mathrm{s}}$, the width of the PS domain increased faster than PLA domain. This behavior contrasts sharply with the lamellae-forming systems without strong inter-chain interactions for which assembly occurs for 1\textless L$_{\mathrm{s}}$/L$_{\mathrm{o}}$ \textless 1.1. Experimental and molecular simulation results will be discussed in the context of non-equilibrium assembly behavior of triblock copolymers, and the potential for chemical complexity and chain architecture to improve the function block polymer materials for lithographic applications.