Reversible and tunable morphologies of amphiphilic block copolymer nanorods confined in nanopores: Roles of annealing solvents

• Published in: Polymer (Guilford) Vol. 228; p. 123859
• Main Authors: Tseng, Yu-Hsuan, Lin, Yu-Liang, Ho, Jhih-Hao, Chang, Chun-Ting, Fan, Yi-Chun, Shen, Ming-Hui, Chen, Jiun-Tai
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 16.07.2021; Elsevier BV
• Subjects: Aluminum; Aluminum oxide; Annealing; Block copolymer; Block copolymers; Ethylene oxide; Functional materials; Materials selection; Microphase separation; Morphology; Nanomaterials; Nanorod; Nanorods; Nanostructure; Nanotechnology; Polymers; Polystyrene; Polystyrene resins; PS-b-PEO; Self-assembly; Solvent vapor annealing; Solvents; Vapors; Wetting; Solvent vapor annealing; Microphase separation; PS-b-PEO; Nanorod; Block copolymer
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2021.123859

In the past few decades, block copolymer nanostructures have been fabricated using porous templates via traditional wetting methods, such as the thermal annealing method and the solution wetting method. The microphase-separated morphologies of most prepared block copolymer nanostructures, however, can only be controlled by tuning the pore sizes of the templates or by changing the molecular weights of the polymer blocks, limiting the potential applications of block copolymer nanostructures. Here, we present an ingenious approach to form polystyrene-block-poly (ethylene oxide) (PS-b-PEO) nanorods in the nanopores of anodic aluminum oxide (AAO) templates via the solvent vapor annealing method. The solvent vapors not only induce the PS-b-PEO chains to wet the nanopores but also control the microphase-separated morphologies of the nanorods. By changing the annealing solvents, the internal morphologies of the PS-b-PEO nanorods can be well-controlled because of the change of the solvent-polymer interactions and the effective volume fractions. When the samples are annealed in THF, THF/water (1:1 by weight), and THF/MeOH (1:1 by weight) vapors, PS-b-PEO nanorods with helical, spherical, and cylindrical morphologies can be achieved, respectively. The sizes of the self-assembled nanodomains are also measured and compared quantitatively. Furthermore, the morphologies of the PS-b-PEO nanorods can be reversibly converted by annealing in different solvents alternately. Thanks to the possibility to selectively introduce precursor materials into the hydrophilic PEO domains of the PS-b-PEO nanorods, this work provides a powerful technique to fabricate functional nanomaterials with unique morphologies for further applications. [Display omitted] •Polystyrene-block-poly (ethylene oxide) (PS-b-PEO) nanorods are formed.•The nanorods are introduced via the solvent vapor annealing method.•PS-b-PEO nanorods with helical, spherical, and cylindrical morphologies can be achieved.•The morphologies of the PS-b-PEO nanorods can be reversibly converted.