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Microphase segregation and selective chain scission of poly(2‐methyl‐2‐oxazoline)‐block‐polystyrene

Tran, Helen, Bergman, Harrison M., de la Rosa, Victor R., Maji, Samarendra, Parenti, Kaia R., Hoogenboom, Richard, Campos, Luis M.
Journal of polymer science 2019 v.57 no.12 pp. 1349-1357
annealing, atomic force microscopy, cleavage (chemistry), composite polymers, copper, hydrophilicity, molecular weight, polymerization, solvents, ultraviolet radiation
Herein, we report the design and synthesis of a block copolymer (BCP) with a high Flory–Huggins interaction parameter to access 10 nm feature sizes for potential lithographic applications. The investigated BCP is poly[(2‐methyl‐2‐oxazoline)‐block‐styrene] (PMeOx‐b‐PS), where the PMeOx segment functions as a hydrophilic segment. Two BCPs with different molecular weights were prepared using PMeOx as macroinitiator for copper(0) mediated controlled radical polymerization. The thin film self‐assembly of the obtained PMeOx‐b‐PS was performed by solvent annealing and investigated by atomic force microscopy. Both polymers formed PMeOx cylinders in a PS matrix with an average cylinder diameter of 10.5 nm. Additionally, the ability of the PMeOx domains to selectively degrade under ultraviolet irradiation was explored. It was shown that scission of the PMeOx block does occur selectively, and furthermore that the degraded domains can be removed while leaving the PS matrix intact. By combining synthetic accessibility, small feature sizes, and a selectively cleavable domain, this new BCP system holds significant promise as a lithographic mask for patterning surfaces with high precision. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1349–1357