(587d) Comparison of the Stability of Perpendicular Lamellae Formed By Linear Block Copolymers and Their Cyclic Analogs

Block copolymer (BCP) thin films with lamellar nanostructures oriented perpendicular to the substrate surface are a potential alternative to traditional photolithography for patterning nanoscale features for the semiconductor industry. Conventionally, A-block-B diblock copolymer architecture has been used extensively for such applications. However, a mismatch in the surface energies of two blocks (A and B) leads to the formation of lamellae oriented parallel to the substrate, which is undesirable for BCP-based nanolithography. Moving to A-block-(B-random-C) block-random copolymer (BRCP) architecture provides a feasible way to control the surface energy of the “random” coblock (B-random-C) relative to A block and thereby controlling the orientation of the nanostructure. Here, we use dissipative particle dynamics simulations to study the thermodynamic phase behavior of BRCPs as a function of the segregation strengths, composition of the coblock, and the interfacial tensions between the blocks. We first verify that; indeed, the interfacial tension can be tuned by tuning the composition of the “random” coblock. We also find that BRCPs have composition-dependent effective segregation strengths at the order-disorder transitions (ODTs) unlike the same molecular weight diblock copolymers where the segregation strength at the ODT is always constant. Comparing the ODTs of BRCPs against the diblock copolymer system maintained at the same effective segregation strengths reveals that BRCPs have a larger window of stability to form the lamellae. We hypothesize that the difference in thermodynamic stabilities of the two systems originates from the differences in the interfacial tension of block-random copolymers from that of diblock copolymers. We aim to develop a predictive model to estimate the ODTs of BRCPs using the information of ODTs of diblock copolymers.

Funding acknowledgment – NSF 1825881