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Dewetting of Swollen Poly(3-hexylthiophene) Films during Spin-Coating Processes: Implications for Device Fabrication
(2018-05-01)
Chung, Pei-Yun
;
Cheng, Ming-Hsiang
;
Tseng, Hsiao-Fan
;
Liu, Chih-Ting
;
Chiu, Tang-Yao
Poly(3-hexylthiophene) (P3HT) films have been usually prepared by spin-coating for the applications of electronic devices such as organic photovoltaic devices (OPV) and organic field-effect transistors (OFETs). The wetting and dewetting behaviors of the swollen P3HT films during the spin-coating processes, however, are still poorly understood. In this work, we investigate the dewetting behaviors of P3HT thin films and the formation of ring structures during the spin-coating process by controlling the spin rates and the solution temperatures. Quantitative studies of the dewetting phenomena are conducted by measuring the sizes of the ring structures of the dewetting patterns. It is observed that the sizes of the ring structures are larger at lower spin rates because of the longer dewetting times allowed during the spin-coating processes. More importantly, the dewetting behaviors of the P3HT films are discovered to be affected by the formation of the P3HT nanowhiskers (nanowires). This work offers a deeper understanding of the dewetting behaviors of swollen P3HT films during the spin-coating processes, which is crucial for the development of P3HT-based optoelectronic devices.
Interplay of Template Constraints and Microphase Separation in Polymeric Nano-Objects Replicated from Novel Modulated and Interconnected Nanoporous Anodic Alumina
(2018-01-01)
Bayat, Haider
;
Lin, Chia-Hua
;
Cheng, Ming-Hsiang
;
Steuber, Marc
;
Chen, Jiun-Tai
We report on a versatile strategy to fabricate shape-controlled polymeric nano-objects with an internal compartmentalized structure by replication from pore-diameter-modulated and interconnected nanoporous anodized aluminum oxide (AAO). The AAO with modulated pore diameters is synthesized in a refined temperature-modulated hard anodization (TMHA) approach, by alternating the flow rate of an air stream cooling the electrolyte. Through pore-widening of the templates with modulated pore diameters, a stable interconnected 3D network with transversal ellipsoidal holes is fabricated as a second template structure. From these unprecedented template structures exhibiting modulated pores and an intricate 3D network structure, shape-controlled polymeric nano-objects are replicated using the melt wetting method with polystyrene homopolymer (PS) and cylinder-forming block copolymer polystyrene-block-polydimethylsiloxane (PS298-b-PDMS195). The replicated nanostructures are separated into individual anisotropically shaped nanocapsules by passing the replicas through a polycarbonate membrane followed by gentle sonication. Inside the nano-objects, the microphase separation of PS298-b-PDMS195 affords parallel aligned nanophases, in which domain sizes and morphologies are different compared to the unconfined bulk according to transmission electron microscopy analyses. These advanced AAO platforms and the nanoscale polymer replicas offer new routes for compartmentalized nano objects with potential future relevance for applications ranging from drug nanocarriers to biosensors.
Controlled Assembly of Polymer-Tethered Gold Nanorods via a Rayleigh-Instability-Driven Transformation: Implications for Biomedical Applications
(2019-05-01)
Chiu, Tang-Yao
;
Cheng, Ming-Hsiang
;
Chang, Chun-Wei
;
Ko, Hao-Wen
;
Chen, Jiun-Tai
We study the assembly and morphology transformation of gold nanorods tethered with polystyrene ligands (AuNRs@PS). The AuNRs@PS nanotubes are first fabricated in the nanopores of anodic aluminum oxide (AAO) templates by the solution wetting method. When the samples are thermally annealed, the Rayleigh-instability-driven transformations of the nanostructures are triggered by the decrease of the interfacial energies between the nanotubes and the inner air cylinders. Four different morphologies are identified: nanotubes (I), undulated structures (II), Rayleigh-instability-induced structures (III), and nanorods (IV). The morphology diagrams of the AuNRs@PS structures using different thermal annealing temperatures and times are also made, showing that the morphology transformation rates are higher at higher annealing temperatures. This work has implications to be applied in different fields such as biomedical applications.
Block copolymer micelles confined in cylindrical nanopores: Effects of annealing solvents and hybridization
(2020-05-01)
Cheng, Ming-Hsiang
;
Yao, I-Chun
;
Chiu, Tang-Yao
;
Chen, Jiun-Tai
;
交大名義發表
Amphiphilic block copolymer micelles have been intensively investigated and applied into various research fields for decades. One of the most promising characteristics for block copolymer micelles is the selective incorporation of metal precursors in the cores or coronas of the micelles. By combining with nanoporous membranes, aligned polymer nanostructures can be generated, facilitating the applications such as nanolithography and catalysis. The morphology transitions and controllability of block copolymer micelles in confined geometries, however, have seldom been studied. In addition, for hybrid micelles in which polymer segments are selectively incorporated with inorganic metal precursors, the relationship between hybridization and morphologies of polymer nanostructures in the confined states is still under discussion. In this work, we investigate the effects of annealing solvents and hybridization with metal precursors (gold(III) chloride trihydrate (HAuCl4 center dot 3H(2)O)) on the morphologies of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer micelles confined in the nanopores of anodic aluminum oxide (AAO) templates. Tuned by the annealing solvent vapors and the selective ion complexation between HAuCl4 and P4VP cores, various morphologies can be effectively controlled, such as the spherical-micelles-in-rod morphology, the parallel-cylinders-in-rod morphology, and the hemispherical-micelles-in-rod morphology. This study not only investigates the effects of annealing solvent vapors and hybridization on the morphologies of block copolymer micelles confined in cylindrical nano-geometries but also offers a viable route for preparing metal nanoparticles embedded in porous templates.
Rayleigh-Instability-Induced Transformation for Confined Polystyrene Nanotubes Prepared Using the Solvent-Vapor-Induced Wetting Method
(1970-01-01)
Fang, Zhi-Xuan
;
Chu, Chien-Wei
;
Tsai, Chia-Chan
;
Chang, Chun-Wei
;
Cheng, Ming-Hsiang
Polystyrene (PS) nanotubes prepared using the solvent-vapor-induced wetting method with anodic aluminum oxide templates are for the first time applied to study the thermal stabilities of polymer nanotubes confined in cylindrical geometries. The morphologies of the PS nanotubes and the corresponding transformed PS nanostructures driven by the Rayleigh instabilities after thermal annealing treatments are characterized by scanning electron microscopy. Morphology diagrams of the Rayleigh-instability-induced nanostructures for PS nanotubes prepared via the solvent-vapor-induced wetting method and the solution wetting method are constructed to study the differences in kinetics for samples using different wetting methods. Slower transformation kinetics for the PS samples prepared by the solvent-vapor-induced wetting method than those prepared by the solution wetting method are observed, indicating the better thermal stabilities and the relatively denser packings of the polymer chains in the nanopores for the PS samples prepared using the solvent-vapor-induced wetting method.
Curved block copolymer nanodiscs: structure transformations in cylindrical nanopores using the nonsolvent-assisted template wetting method
(2019-11-07)
Lin, Yu-Liang
;
Cheng, Ming-Hsiang
;
Chang, Chun-Wei
;
Chu, Chien-Wei
;
Liu, Chih-Ting
In this work, we study the structure transformations of cylinder-forming polystyrene-block-polydimethylsiloxane (PS31k-b-PDMS14.5k) confined in cylindrical nanopores. PS-b-PDMS nanotubes, nanospheres, and curved nanodiscs are ingeniously prepared by a facile template wetting strategy using anodic aluminum oxide (AAO) templates. Quantitative analyses of the structure transformations from nanospheres to curved nanodiscs are also conducted, showing that the lengths of the curved nanodiscs can be controlled by adjusting the annealing temperature and time. Furthermore, the PDMS domains of the nanostructures can be selectively etched using HF solutions, generating porous PS nanostructures. This work not only offers versatile routes to prepare block copolymer nanostructures with controlled shapes but also provides a deeper understanding of the structure transformation of block copolymers in confined geometries.
Hierarchical hybrid nanostructures: controlled assembly of polymer-encapsulated gold nanoparticles via a Rayleigh-instability-driven transformation under cylindrical confinement
(2016-01-01)
Ko, Hao-Wen
;
Chang, Chun-Wei
;
Chi, Mu-Huan
;
Chu, Chien-Wei
;
Cheng, Ming-Hsiang
We develop a novel route based on the solution wetting method using anodic aluminum oxide (AAO) templates to fabricate hierarchical hybrid nanostructures assembled from polystyrene-encapsulated gold nanoparticles (Au@PS NPs). Hybrid nanostructures including nanotubes and nanospheres can be reliably prepared, in which the spatial arrangement of the Au@PS NPs is determined by the pore diameters of the templates and the molecular weights of the thiol-ended polystyrene (PS-SH) ligands. In particular, the Rayleigh-instability-driven transformation plays a key role in the formation of the hybrid nanospheres.
Controlled self-assemblies of polystyrene-block-polydimethylsiloxane micelles in cylindrical confinement through a micelle solution wetting method and Rayleigh-instability-driven transformation
(2017-08-28)
Ko, Hao-Wen
;
Higuchi, Takeshi
;
Chang, Chun-Wei
;
Cheng, Ming-Hsiang
;
Isono, Komei
Block copolymer micelles have been extensively discussed for many decades because of their applications, such as lithography and drug delivery. However, controlling the morphologies of nanostructure assembly using block copolymer micelles as building elements remains a great challenge. In this work, we developed a novel route to induce micelle assembly in confined geometries. Polystyrene-block-polydimethylsiloxane (PS-b-PDMS) micelle solutions were used to prepare micelle nanostructures, and the critical parameters affecting the morphologies were determined. Micelle nanorods, micelle nanospheres, and multi-component nanopeapods were prepared by wetting anodic aluminum oxide (AAO) templates with micelle solutions. Rayleigh-instability-driven transformation was discovered to play an important role in controlling the morphologies of the micelle nanostructures. This study not only proposes a versatile approach to preparing block copolymer micelle nanostructures, but it also provides deeper insight into the controlling factors of block copolymer micelle morphologies in cylindrical confinement.
Solvent On-Film Annealing (SOFA): Morphological Evolution of Polymer Particles on Polymer Films via Solvent Vapor Annealing
(2017-07-11)
Tseng, Hsiao-Fan
;
Cheng, Ming-Hsiang
;
Li, Jia-Wei
;
Chen, Jiun-Tai
;
應用化學系
Over the past few decades, anisotropic polymer particles are of significant interest because of their unique properties which can be applied in various areas, such as drug delivery, biotechnology, and electronics. Most approaches to synthesize anisotropic polymer particles, however, are complicated, and the three-dimensional shapes of the anisotropic particles are usually difficult to be controlled. In this work, we develop a solvent on-film annealing (SOFA) method to fabricate anisotropic polymer particles by studying the morphological evolution of polystyrene (PS) microspheres on poly(methyl methacrylate) (PMMA) films annealed in toluene vapor. At different annealing stages, the isotropic PS microspheres gradually transform to anisotropic PS particles with different morphologies, such as UFO-, cymbal-, peanut-, and bowl-shaped particles. The morphology evolution is driven by the surface and interfacial tensions during the annealing processes and can be confirmed by a selective removal technique. Acetic acid, a selective solvent for PMMA, and cyclohexane, a selective solvent for PS, are also used as the annealing solvents to further investigate the effect of the annealing solvent.
Blending Homopolymers for Controlling the Morphology Transitions of Block Copolymer Nanorods Confined in Cylindrical Nanopores
(2017-06-21)
Cheng, Ming-Hsiang
;
Hsu, Yu-Chen
;
Chang, Chun-Wei
;
Ko, Hao-Wen
;
Chung, Pei-Yun
The microphase separation of block copolymers in confined geometries has been widely investigated over the last few decades. The controllability and versatility of the confinement-induced morphologies, however, are still difficult to be achieved because of the limited experimental parameters in the process of fabricating the confined nanostructures. In this work, we study the morphology transitions of lamellae forming polystyrene-block-polydimethylsiloxane (PS-b-PDMS) nanorods confined in the nanopores of anodic aluminum oxide (AAO) templates. The nanorods are formed by solvent-assisted template wetting, and the morphologies are compared to those in the bulk state. By blending PS-b-PDMS with homopolystyrene (hPS), the morphologies of the nanorods can be controlled because of the changes of the effective volume fractions. Special morphology transitions from concentric lamellar morphology, to multihelical morphology, and finally to spherical-like morphology are observed by increasing the weight ratios of hPS. hPS with different molecular weights is also applied to investigate the effect of hPS on the morphologies of the PS-b-PDMS/hPS blend nanostructures. The unusual morphologies are further confirmed by a selective removal process, which also generates nanochannels for possible refilling with functional materials.

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