Fabrication of High χ-Low <i>N</i> Block Copolymers with Thermally Stable Sub-5 nm Microdomains Using Polyzwitterion as a Constituent Block

Nanopatterns with a sub-5 nm line width are of great interest due to their potential applications in nanotechnology. Herein, we report the design and synthesis of three-component bolaform giant surfactants that can assemble into three-phase-four-layer lamellar (LAM3) structures with sub-5 nm feature sizes. These samples consist of central linear polystyrene (PS) chains with oligodimethylsiloxane-functionalized polyhedral oligomeric silsesquioxane (SiPOSS) at one end and perfluoroalkyl-functionalized POSS (FPOSS) at the other end. Phase separation occurs among three mutually incompatible components, leading to LAM3 structures with relatively sharp interfaces and d-spacings of 12–19 nm. While the lamellar periodicity can be facilely tuned by changing the chain length of PS, the pitch widths of the POSS domains remain largely constant. Energy-dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) were used to analyze the elemental distribution of the LAM3 structures. After oxygen plasma treatment, the morphology converts into a hierarchical lamellar structure with extremely small Si-rich layers (∼2 nm in thickness). This work suggests that these bolaform giant surfactants are versatile counterparts of traditional triblock copolymers capable of undergoing rapid and strong phase separation at relatively low molecular weights toward unconventional nanostructures with small feature sizes.

Section: Introductionmentioning

confidence: 99%

Three-Component Bolaform Giant Surfactants Forming Lamellar Nanopatterns with Sub-5 nm Feature Sizes

Shao

Hou

et al. 2023

“…14 Deng et al reported 15 a low molar mass poly(pentadecafluorooctyl methacrylate)-b-polyhydroxystyrene (PPDFMA−PHS) (N = 38) forming nanodomains with a characteristic size of 9.8 nm. Recently, Xu et al used 16 poly(styrene-b-(4-vinylpyridine)propane-1-sulfonate) (PS− PVPS) with N = 21 to obtain a lamellar phase with a periodicity of 5.7 nm.…”

Section: Introductionmentioning

confidence: 99%

Chain Flexibility Effects on the Self-Assembly of Diblock Copolymer in Thin Films

Chen

Zhu

et al. 2023

We investigate the effects of chain flexibility on the self-assembly behavior of symmetric diblock copolymers (BCPs) when they are confined as a thin film between two surfaces. Employing worm-like chain (WLC) self-consistent field theory, we study the relative stability of parallel (L∥) and perpendicular (L⊥) orientations of BCP lamellar phases, ranging in chain flexibility from flexible Gaussian chains to semiflexible and rigid chains. For flat and neutral bounding surfaces (no surface preference for one of the two BCP components), the stability of the L⊥ lamellae increases with chain rigidity. When the top surface is flat and the bottom substrate is corrugated, increasing the surface roughness enhances the stability of the L⊥ lamellae for flexible Gaussian chains. However, an opposite behavior is observed for rigid chains, where the L⊥ stability decreases as the substrate roughness increases. We further show that as the substrate roughness increases, the critical value of the substrate preference, u*, corresponding to an L⊥-to-L∥ transition, decreases for rigid chains, while it increases for flexible Gaussian chains. Our results highlight the physical mechanism of tailoring the orientation of lamellar phases in thin-film setups. This is of importance, in particular, for short (semiflexible or rigid) chains that are in high demand in emerging nanolithography and other industrial applications.

“…In general, the key to design high χ-low N BCPs is to find two components with quite different physical and chemical properties. , Such incompatibility often arises from the difference of hydrophilicity between blocks. Based on this principle, polymers containing fluorine, silicon, polar/ionic groups, and crystalline/liquid crystalline moieties are used as the candidates.…”

Section: Introductionmentioning

confidence: 99%

Geometry-Modulated Self-Assembly Structures of Covalent Polyoxometalate–Polymer Hybrid in Bulk and Thin-Film States

Wang

Hong

et al. 2022

This work reports the synthesis, characterization, and self-assembled structures of three series of Keggin-type polyoxometalate (POM)-based hybrid molecules KPOM- m PS n ( m = 1, 2 and 3), in which one, two, or three polystyrene (PS) chains are covalently attached to a POM head, respectively. The classical “click” reaction was applied to prepare samples with predesigned molecular geometry, which were further purified by C18 reversed-phase high-performance liquid chromatography (RP-HPLC). Strong chemical incompatibility between inorganic POMs and organic PS chains drives the hybrid molecules to microphase separate into versatile nanostructures in both bulk and thin-film states. In thermally annealed bulk samples, four phase morphologies were found depending on both the overall molecular geometry and the volume fractions of PS tails, including lamellae (LAM), hexagonal packed cylinders (HEX), disordered micelles (DM), and body-centered cubic (BCC) packed spheres, as revealed by small-angle X-ray scattering (SAXS). In the thin-film state, LAM, HEX, and BCC structures were observed and proved by transmission electron microscopy (TEM) images and grazing incidence SAXS (GISAXS). This work expands the scope of self-assembled nanostructures of POM-based hybrid materials to spherical phases and provides a platform for the study of the basic physical principles of their self-assembly behavior.