Isomeric Effect Enabled Thermally Driven Self-Assembly of Hydroxystyrene-Based Block Copolymers

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• 作者：Catherine Kanimozhi ; Myungwoong Kim ; Steven R. Larson ; Jonathan W. Choi ; Youngwoo Choo ; Daniel P. Sweat ; Chinedum O. Osuji ; Padma Gopalan
• 刊名：ACS Macro Letters
• 出版年：2016
• 出版时间：July 19, 2016
• 年：2016
• 卷：5
• 期：7
• 页码：833-838
• 全文大小：414K
• 年卷期：0
• ISSN：2161-1653

文摘

We demonstrate through isomeric effect the modulation of thermal properties of poly(hydroxystyrene) (PHS)-based block copolymers (BCPs). A minimal structural change of substituting 3HS for 4HS in the BCP results in a drastic decrease in T_g, which in turn enables the thin film assembly of the BCP via thermal annealing. We synthesized a series of poly(3-hydroxystyrene-b-tert-butylstyrene) [P(3HS-b-tBuSt)] and poly(4-hydroxystyrene-b-tert-butylstyrene) [P(4HS-b-tBuSt)] BCPs by sequential anionic polymerization of protected 3HS/4HS monomer and tBuSt followed by deprotection. Measured T_g of P(3HS) was ∼20–30 °C lower than P(4HS) of comparable molecular weights. As a result, thermally driven self-assembly of P(3HS-b-tBuSt) BCPs in both bulk and thin film is demonstrated. For P(4HS-b-tBuSt) thermal annealing in thin-film at high temperatures results in poorly developed morphology due to cross-linking reaction of the 4HS block. The smallest periodicity observed for P(3HS-b-tBuSt) was 8.8 nm in lamellar and 11.5 nm in cylindrical morphologies. The functionality of the 3HS block was exploited to incorporate vapor phase metal oxide precursors to generate sub-10 nm alumina nanowires.