Abstract
We present a feasible approach to the direct development of three-dimensionally (3D) bicontinuous gyroid (GYR) nanostructure in high-molecular-weight, composition-controlled polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) films. The use of a neutral solvent vapor to elaborately control the swelling of block copolymer (BCP) films is essential to generate a direct pathway to GYR (or giant GYR) structure through a hexagonal (HEX) cylindrical morphology in the same material, because the thermal ordering of highly entangled BCP imposes the limit on the chain mobility. Along with the improved mechanical strength arising from the high molecular weight property of the polymers, the structural integrity and overall excellence of a large-scale GYR morphology were confirmed by the results of membrane performance, which showed greater permeability through the nanoporous GYR structure up to by a factor of three than that through the HEX structure. Moreover, a 3D nanoporous GYR template was applied to an affordable material to reproduce an inverse skeletal replica of the GYR structure with its structure being uniformly interconnected. This simple approach to the GYR template, owing to its structural tunability in a controlled composition of BCP, is anticipated to be applicable to a wide range of materialization for practical systems.
Highlights
Materialization of well-organized, uniform nanostructures has currently been a challenge to meet the increasing demands for these materials in high-performance and high-precision applications such as high-density data storage[1,2], bio-sensors[3,4], water filtration[5,6,7], controlled drug release[8,9], and nanoscale replication[10,11,12]
A 0.5-μm-thick block copolymer (BCP) film was prepared onto a standard Si substrate and subjected to the solvent vapor annealing (SVA) process with tetrahydrofuran (THF) vapor as a neutral solvent for both blocks of PS-b-PMMA
This schematic represents that a morphological transition through a hexagonal (HEX) cylinder to a gyroid (GYR) morphology occurred during the time-controlled SVA process
Summary
Materialization of well-organized, uniform nanostructures has currently been a challenge to meet the increasing demands for these materials in high-performance and high-precision applications such as high-density data storage[1,2], bio-sensors[3,4], water filtration[5,6,7], controlled drug release[8,9], and nanoscale replication[10,11,12]. The chain mobility of high- and ultrahigh-molecular-weight BCPs could readily be accelerated by applying a solvent vapor annealing (SVA) process, and the long-range ordered morphologies have typically been regulated by annealing them for an appropriate period of time with a neutral solvent[19,20]. The brush-type BCP chain architecture forms densely grafted side chains along the main chains, and the side chains with the different chemical identity are generally less entangled and radially stretched from the mainchains, eventually leading to a greater chain mobility for ordering of high-molecular-weight BCPs. the formation of three-dimensional (3D) textures from BCP self-assembly has been studied in the pursuit of developing new transport characteristics owing to the structurally interconnected pathways found in these materials.
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