Rational Design of a Block Copolymer with a High Interaction Parameter

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• 作者：Daniel P. Sweat ; Myungwoong Kim ; Steven R. Larson ; Jonathan W. Choi ; Youngwoo Choo ; Chinedum O. Osuji ; Padma Gopalan
• 刊名：Macromolecules
• 出版年：2014
• 出版时间：October 14, 2014
• 年：2014
• 卷：47
• 期：19
• 页码：6687-6696
• 全文大小：728K
• ISSN：1520-5835

文摘

A series of poly(4-tert-butylstyrene-block-2-vinylpyridine) [P(tBuSt-b-2VP)] block copolymers (BCPs) with varying volume fractions, molecular weights, and narrow dispersities were synthesized from the commercially available monomers by sequential living anionic polymerization. The copolymers were thoroughly characterized by ¹H NMR spectroscopy, size exclusion chromatography, thermal gravimetric analysis, and differential scanning calorimetry (DSC). To examine the effect of the tert-butyl group on the effective interaction parameter (蠂_eff) relative to poly(styrene-block-2-vinylpyridine) [(P(S-b-2VP)], the self-assembly of symmetric copolymers was studied by small-angle X-ray scattering (SAXS) and transmission electron microscopy. Order-to-disorder transitions (ODTs) were identified by both DSC and SAXS on five copolymers, to define the equation 蠂_eff(T) = (67.9 卤 1.3)/T 鈥?(0.0502 卤 0.0029), which shows a higher enthalpic contribution to 蠂_eff than P(S-b-2VP) and approximately 1.5 times larger 蠂_eff. This enables a minimum full pitch of 9.6 nm for the symmetric copolymers. Asymmetric copolymers were also examined for bulk self-assembly by SAXS and TEM, exploring both P2VP and PtBuSt cylindrical phases with diameters as small as 6 nm. Feasibility of thin film assembly by thermal annealing was demonstrated for a P2VP cylinder forming BCPs to yield parallel cylinders that were seeded with Pt ions and etched to yield Pt nanowires with diameters as small as 5.8 nm.