Preparation of diblock copolymer films for the localization of C60 and multiwalled carbon nanotubes on aqueous substrate

Abstract

Dropping polystyrene-block-poly(ethylene oxide) (PS-b-PEO) solution on a still and clean water surface caused the formation of homogeneous films of diblock copolymer at the organic vapor/water interface. The morphologies of the PS-b-PEO were studied to control and modulate the arrangement of ordered structures by applying different solvents at different annealing times. After 24 h of annealing under toluene vapor, a lamellar morphology was produced, whereas a cylindrical morphology was produced under chloroform vapor. This simple method was used to obtain more than one type of ordered microdomain structure using the same symmetric diblock copolymer. Interestingly, the microdomain size reached 120 nm, much larger than that obtained by bulk or solution self-assembly. The microphase-separated PS-b-PEO copolymer was utilized as a novel template for the selective self-assembly of the polymer-functionalized C₆₀ and the carbon nanotubes (CNTs) by combining aqueous substrate with solvent annealing. The PS-grafted C₆₀ enhanced the PS-b-PEO to form a lamellar microstructure. The PS-grafted C₆₀ accommodated in the PS phase expanded the scale of PS domains. The PEO-covered CNTs were prepared to form a PEO-covered CNT/water solution for application to a complex substrate with diblock copolymer templates. This methodology enables accommodation of a selective assembly of the CNTs onto the PEO phase. This assembly strategy is a versatile approach and may open a new route for the controlled assembly of anisotropic nanostructured materials with desirable patterns on soft substrate.