Quantify the contribution of chain length heterogeneity on block copolymer self-assembly

This work quantitatively explores the effect of chain length heterogeneity on self-assembly behaviors of block copolymer, focusing on the narrow distribution region. A library of discrete diblock copolymers consisting of oligo dimethylsiloxane (oDMS) and oligo lactic acid (oLA) blocks were modularly prepared with one monomer difference in composition, which form highly ordered nanostructures at room temperature. The molecular weight distribution of the oLA block was then precisely modulated through a reconstruction approach, achieving an absolute control on chain length heterogeneity. By meticulously tuning the breadth and symmetry of the distribution profile, the lattice dimension of the assembled nanostructure significantly expands, while no appreciable difference on the phase stability was observed. This work provides an explicit access to block copolymers with narrow dispersity that are not possible through conventional chemical approach, revealing the critical contribution of dispersity on selfassembly and bridging the existing gaps between experiments and theories.