Although one-dimensional polymer nanomaterials can be prepared by approaches such as the template method, the control over the morphologies of one-dimensional polymer nanomaterials containing multiple components is still a great challenge. In this work, we investigate the formation of polymer nanopeapods using a novel double-solution wetting method in the nanopores of anodic aluminum oxide (AAO) templates. A polystyrene (PS) solution in dimethylformamide (DMF) is first introduced into the nanopores of the AAO templates. Then a second polymer solution of poly(methyl methacrylate) (PMMA) in acetic acid is infiltrated into the nanopores. Because of the stronger interaction between acetic acid and aluminum oxide than that between DMF and aluminum oxide, the PMMA solution preferentially wets the pore walls of the templates and the PS solution is isolated in the center of the nanopores. After the evaporation of the solvent, peapod-like PS/PMMA nanostructures are obtained, where the shell and the core are composed of PMMA and PS, respectively. The compositions of the polymer nanopeapods are confirmed by removing PS or PMMA selectively. The formation mechanism of the nanostructures is related to the Rayleigh-instability-type transformation and further studied by changing experimental parameters such as the polymer concentration or the polymer molecular weight. This work not only provides a simple approach to prepare multicomponent polymer nanomaterials with controlled morphologies and sizes, but also contributes to a deeper understanding of polymer−solvent interactions in confined geometries.

One-dimensional polymer nanomaterials are prepared by a microwave-annealing-induced nanowetting (MAIN) method using anodic aluminum oxide templates.

We study the formation of porous polymer nanostructures fabricated by the surface-induced phase separation of polymer solutions in anodic aluminum oxide (AAO) templates. Poly(methyl methacrylate) (PMMA) and tetrahydrofuran (THF) are used to investigate the evolution process of the surface-induced phase separation. With the longer immersion time of the AAO template in the polymer solution, the size of the solvent-rich droplet is increased by the coarsening process, resulting in the formation of porous polymer nanostructures. The coarsening mechanism is further evaluated by changing the experimental parameters including the immersion time, the polymer concentration, the polymer molecular weight, and the solvent quality. Under conditions in which polymer solutions have higher viscosities, the coarsening process is slowed down and the formation of the porous nanostructures is prohibited. The prevention of the porous nanostructures can also be realized by adding water to the PMMA/THF solution before the immersion process.

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.

Spherical core−shell structures have been widely investigated in recent years, and they can be used for various applications, such as drug delivery, biological labeling, and batteries. Although many methods have been developed to prepare core−shell structures, it is still a great challenge to fabricate core−shell structures in the nanoscale with wellcontrolled morphologies and sizes. In this work, we present a simple method to fabricate core−shell polymer nanospheres consisting of polystyrene (PS) cores and poly(methyl methacrylate) (PMMA) shells. The nanostructures are prepared by a solution-based template wetting method. After the nanopores of anodic aluminum oxide (AAO) templates are wetted sequentially by PS/PMMA blend solutions and water, the core−shell nanostructures can be formed. The formation process is related to the Rayleigh-instability-type transformation. Selective removal techniques are also used to confirm the morphologies of the core− shell nanostructures. S pherical core−shell structures have attracted significant attention in recent years. Because of the special morphology and the characteristic of multicomponents, they can be used in different applications, such as drug delivery, biological labeling, and batteries. 1−3 For polymers, most researches focus on preparing core−shell structures in micrometer sizes. 4−9 Preparation of spherical polymer core−shell structures in the nanometer sizes with controlled morphologies, however, is still a great challenge. Here, we present a feasible template wetting method to fabricate core−shell polymer nanospheres using polystyrene (PS)/poly(methyl methacrylate) (PMMA) blend solutions.The template wetting method, pioneered by Martin et al., is a powerful approach to prepare one-dimensional nanomaterials. 10,11 One of the most commonly used templates is the anodic aluminum oxide (AAO) template, which can be prepared by the anodization of aluminum foils. 12,13 In general, there are three major ways to use the template wetting method to introduce polymers into the nanopores of porous templates, including the melt method, the solvent annealing method, and the solution method. 14−20 Compared to the other two methods, the solution method is more versatile considering the various experimental parameters that can be used. In the solution method, polymer chains are first dissolved in suitable solvents, and the polymer solutions wet the nanopores via capillary force. Tunable parameters such as the type of solvent, the concentration of solution, the interfacial tension, the immersing time, and the drying condition can be changed in the solution method. 15,21−23 Here, we use the solution method to fabricate the core−shell polymer nanospheres, which is related to the confinement effect of the cylindrical nanopores, the nonsolvent effect, and the surface-induced phase separation. For the confinement effect, the sizes of polymer nanostructures are controlled by the pore sizes of the templates. For the nonsolvent effect, we have previously studied the morphologies of polym...