Nanostructure sizes and interfacial rougness in blends of linear and cyclic block copolymers*

Cyclic block copolymers (BCPs) are predicted to assemble into nanostructured domains up to 40% smaller than their linear analogues while exhibiting superior thin film stability and assembly dynamics, properties that are desirable nanolithography. However, synthesizing large quantities of high purity cyclic BCPs is challenging. Thus, we employ dissipative particle dynamic (DPD) simulation to probe the self-assembly behavior of cyclic/linear BCP blends with the aim of answering two questions: How much impact do linear impurities have on cyclic BCP nanostructure size? Can cyclic BCPs be used as structure-directing agents to shrink the domains of linear BCPs in majority-linear blends? Our simulations indicate that up to 10% linear impurity in a cyclic BCP product has a negligible impact on domain spacing and interfacial width, suggesting that costly post-synthesis purification of cyclic BCPs to remove linear impurities may be unnecessary. In majority-linear BCP blends, we find that domain spacing decreases in direct proportion to the amount of cyclic BCP in the blend. These findings provide guidance to experimentalists wishing to utilize cyclic BCPs in nanolithography applications.