Limits of Directed Self-Assembly in Block Copolymers.

Gadelrab, Karim R; Ding, Yi; Pablo-Pedro, Ricardo; Chen, Hsieh; Gotrik, Kevin W; Tempel, David G; Ross, Caroline A; Alexander-Katz, Alfredo · Nano Lett · 2018

basic_science · Level V

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Abstract

Understanding the conditions under which defects appear in self-assembling soft-matter systems is of great importance, for example, in the development of block-copolymer (BCP) nanolithography. Here, we explore the limits of the directed self-assembly of BCPs by deliberately adding random imperfections to the template. Our results show that defects emerge due to local "shear-like" distortions of the polymer-template system, a new mechanism that is fundamentally different from the canonical mechanisms of 2D melting. Furthermore, our results provide a general criterion for melting, obtaining the highest tolerance to random deviations from the perfect template at about 0.1 L<sub>0</sub>, where L<sub>0</sub> is the natural BCP periodicity. These findings establish the limits of directed self-assembly of BCPs and can be extended to other classes of materials with soft interactions.