Self-Assembled Copolymer Adsorption Layer-Induced Block Copolymer Nanostructures in Thin Films

Constructing a Comprehensive Nanopattern Library through Morphological Transitions of Block Copolymer Surface Micelles via Direct Solvent Immersion

This study establishes a comprehensive library of nanopatterns achievable by a single block copolymer (BCP), ranging from spheres to complex structures like split micelles, flower-like clusters, toroids, disordered micelle arrays, and unspecified unique shapes. The ordinary nanostructures of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) surface micelles deposited on a SiOx surface undergo a unique morphology transformation when immersed directly in solvents. Investigating parameters such as immersion solvents, BCP molecular weight, substrate interactions, and temperature, this work reveals the influence of these parameters on the thermodynamics and kinetics governing the morphology transformation. Additionally, the practical application of BCP nanopattern templates for fabricating metal nanostructures through direct solvent immersion of surface micelles is demonstrated. This approach offers an efficient and effective method for producing diverse nanostructures, with the potential to be employed in nanolithography, catalysts, electronics, membranes, plasmonics, and photonics.

Influence of Selected Factors on the Adsorption Layer Structure of Polyamino Acids and Their Block Copolymers at the Solid-Aqueous Solution Interface

The adsorption mechanism of different polymers containing ionic polyamino acids monomers in the chain structure at the solid-liquid interface was investigated. Initially, the influence of molecular weight and solution pH on simple polyamino acids (poly(L-aspartic acid) and poly(L-lysine) binding was determined. Considering the obtained dependencies, the polymer adsorption layer conformation was proposed in the systems containing block copolymers (both diblock and symmetrical triblock) consisting of polypeptide as well as poly(ethylene glycol) fragments. The presented studies focused on the application of two experimental methods. The polymer adsorption was carried out using the batch method and the adsorbate concentration was determined spectrophotometrically. Then, the turbidimetric measurements were taken. The analysis of the obtained results showed that the adsorption process of block copolymers depends on two factors. Firstly, the solution pH determines both the nature of the interactions of the copolymer structural units with the solid surface and the conformation of the polypeptide chains. The second parameter influencing the adsorption layer structure is the ratio of the lengths of both blocks. Introducing a short PEG fragment into the polymer main chain may improve the polymer adsorption properties by increasing the number of interactions with the adsorbent surface.

Scaling Laws for Block Copolymer Surface Micelles

Polymers under confinement exhibit different structures and properties from the bulk. While block copolymers (BCPs) create well-defined micelles in solution, two-dimensional (2D) spatial confinement at the air-water interface constrains the chain conformations and deforms the micellar structure, thus forming a surface micelle. The BCP surface micelles open up an opportunity in nanoscience and engineering by serving as an interfacial modifier and structural platform. Nevertheless, a scaling law, a principle governing the micellar structure, is absent. Herein, we report a unified scaling relation to describe the combinational structure of BCP surface micelles in two and three dimensions and further reveal their formation mechanism in line with the suggested scaling relation. We investigated the intrinsic scaling relations in a surface pressure-free environment by introducing a concept of excluded volume-dependent scaling exponent based on the scaling theory of 2D polymers. In addition, an extrinsic scaling relation is derived for the surface pressure-dependent corona scaling.

Block copolymer self-assembly assisted fabrication of laterally organized- and stacked- nanoarrays

Block copolymer (BCP) self-assembly processes are often seen as reliable techniques for advanced nanopatterning to achieve functional surfaces and create templates for nanofabrication. By taking advantage of the tunability in pitch, diameter and feature-to-feature separation of the self-assembled BCP features, complex, laterally organized- and stacked- multicomponent nanoarrays comprising of gold and polymer have been fabricated. The approaches not only demonstrate nanopatterning of up to two levels of hierarchy but also investigate how a variation in the feature-to-feature gap at the first hierarchy affects the self-assembly of polymer features at the second. Such BCP self-assembly enabled multicomponent nanoarray configurations are rarely achieved by other nanofabrication approaches and are particularly promising for pushing the boundaries of block copolymer lithography and in creating unique surface architectures and complex morphologies at the nanoscale.

Nanoscratch-Directed Self-Assembly of Block Copolymer Thin Films

Directed self-assembly (DSA) of block copolymer (BCP) thin films is of particular interest in nanoscience and nanotechnology due to its superior ability to form various well-aligned nanopatterns. Herein, nanoscratch-DSA is introduced as a simple and scalable DSA strategy allowing highly aligned BCP nanopatterns over a large area. A gentle scratching on the target substrate with a commercial diamond lapping film can form uniaxially aligned nanoscratches. As applied in BCP thin films, the nanoscratch effectively guides the self-assembly of overlying BCPs and provides highly aligned nanopatterns along the direction of the nanoscratch. The nanoscratch-DSA is not material-specific, allowing more versatile nanofabrication for various functional nanomaterials. In addition, we demonstrate that the nanoscratch-DSA can be utilized as a direction-controllable and area-selective nanofabrication method.

Universal Interfacial Control through Polymeric Nanomosaic Coating for Block Copolymer Nanopatterning

The employment of self-assembly of soft materials has been accepted as an inexpensive, robust, and reliable patterning method. As their self-assembly relies on the delicate molecular interactions near the substrate, a precise prediction/control of the interface structure and dynamics is critical to achieve desired nanostructures. Herein, a polymeric nanomosaic (PNM) pattern is created from the air/water interfacial self-assembly of a block copolymer (BCP) and introduced as an effective interfacial energy control for substrates. As a demonstration, the PNM coating is employed to control the BCP film structures. The perpendicular orientation of BCP self-assembly, which requires neutral wetting conditions for both blocks, is difficult to achieve but can readily be obtained with the PNM coating upon a fine resolution of the pattern quality. The universal applicability of the PNM coating as an interfacial control has been confirmed on curved, flexible, and three-dimensional substrates. In addition, the PNM is introduced as an etching-free and reusable topcoat imparting free surface neutralization even for the high-χ BCP nanopatterning.