Blending Homopolymers for Controlling the Morphology Transitions of Block Copolymer Nanorods Confined in Cylindrical Nanopores

Abstract

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.

Wettability and Applications of Nanochannels

“…This work demonstrated the size and morphology of polymeric nanomaterials could be simply regulated by using nonsolvent like water. Recently, Chen et al further investigated the morphology transitions of PS‐ b ‐PDMS nanorods filled in the nanochannels of AAO templates, and the nanorods were formed by toluene‐assisted template wetting . By blending PS‐ b ‐PDMS with PS, concentric lamellar morphology, multihelical morphology, and spherical‐like morphology, could be obtained at different polystyrene ratios.…”

“…Chen and co‐workers further studied the water effect on the PMMA nanomaterials formation in the nanochannels of the AAO template, indicating polymeric nanospheres or nanorods were formed with adding water to the polymeric solution, and polymeric nanotubes were obtained without adding water . PS‐ b ‐PDMS were also fabricated by Chen et al confined in the AAO nanochannels, and by regulation the weight ratios of PS, diverse morphologies of PS‐ b ‐PDMS nanomaterials were formed, containing nanorods, concentric lamellar, multihelical and spherical‐like morphology . Moreover, Steinhart et al reported confinement of PMMA/liquid‐crystal nanotubes containing ≈30 nm thick PMMA outside layer and a 5–10 nm thick liquid‐crystalline inside layer in the AAO nanochannels .…”

Dewetting of Swollen Poly(3-hexylthiophene) Films during Spin-Coating Processes: Implications for Device Fabrication

“…The above results demonstrate that the spin rates play a critical role in the dewetting process; at lower spin rates, the samples are surrounded by the solvent molecules for longer times, allowing the formation of ring structures with larger sizes. After the evaporation of the solvents and the formation of the dewetting patterns, it is interesting to see whether or not the dewetting processes can be continued using solvent annealing by placing the dewetted samples in solvent annealing chambers. − For the dewetted P3HT films using P3HT solution in chloroform at 30 °C and spin-coated at 2000 rpm, the samples were first dried and then annealed in solvent (chloroform) vapors. The mechanism of the solvent annealing process and the AFM results at different annealing times are shown in Figure .…”

Synthetic advances of internally nanostructured polymer particles: From and beyond block copolymer

“…Designing BCPs with different volume fractions of segments has been reported. [68] Typically, four methods are used to introduce polymer chains into the internal space of porous templates, including solution wetting, solvent vapor annealing, microwave annealing and melt wetting method. For solution wetting, polymers are dissolved in a good solvent to form a homogeneous solution and then the AAO membrane can be wetted by the solution by capillary force.…”