Functionalizing Nonfunctional Surfaces: Creation of Metal Oxide Nanopatterns on High-Performance Polymers via Self-Assembly of PS- b-PEO

Abstract

High-performance polymers are pivotal for a wide range of applications due to their excellent mechanical, chemical, and thermal properties. This work introduces, for the first time, a block copolymer (BCP) self-assembly method to modify the surfaces of different high-performance polymers. Using highly ordered poly(styrene-b-ethylene oxide) (PS-b-PEO) thin films as templates, metallic oxide nanopillars (Al₂O₃, Ag₂O, MgO, CaO, and TiO₂) with a 20 nm average diameter were fabricated. These were created on high-performance polymer substrates, specifically, polyetheretherketone (PEEK), carbon fiber-reinforced polyetheretherketone (CFPEEK), and ultrahigh molecular weight polyethylene. This method addresses the low chemical activity of these polymeric substrates, offering a cost-effective, scalable solution to produce their surface functionalization. Characterization via atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy validate the structure and composition of the nanostructured surfaces. The significance of BCP self-assembly is emphasized as an effective and versatile approach for the nanoscale tailoring of surface properties in high-performance polymers. This process offers a straightforward method with low technological and energetic costs, paving the way for the extensive surface modification of large areas. The implications of this work extend to various sectors, including biomedical devices, sensors, and electronics, showcasing the broad applicability of this nanoscale tailoring technique.

Keywords: block copolymer self-assembly; high-performance polymers; metal oxide nanopatterns; nanopatterning methodologies; nanostructures; surface functionalization; surface modification techniques.

Figure 1

Process diagram for the deposition of metal oxides onto polymeric substrates.

Figure 2

Effect of the SVA. Letters from (A) to (I) corresponds to AFM images, Insets correspond to FFT images for each AFM image.

Figure 3

Roughness profiles for PEEK (A), CFPEEK (B), and UHMWPE (C) in the different stages of the production of self-assembled PS-b-PEO thin film coatings. (The roughness profiles are determined from the images shown in Figure 2, the zones of each AFM image used can be found in Figure S2 in SI.).

Figure 4

SEM images of PEO vertical cylinders on PS-b-PEO coated substrates after SVA: (A) PEEK, (B) CFPEEK, and (C) UHMWPE. Each panel displays the SEM image (top) and a zoomed-in region (inset). Panels (D–F) show the corresponding size distribution histograms calculated from the SEM images for (A–C), respectively, including the extracted average diameters.

Figure 5

AFM images (left) and corresponding Power Spectral Density (PSD) functions (right) for PS-b-PEO coated substrates after the SVA step: (A, B) PEEK, (C, D) CFPEEK, and (E, F) UHMWPE. PSD plots are calculated from the Fast Fourier Transform (FFT) images shown as insets in the AFM panels and are used to extrapolate the center-to-center distance (D_C–C) between the nanopores. AFM images with particle masks used for D_C–C calculation are provided in Figure S1 in the Supporting Information.

Figure 6

SEM images of metal oxide nanopillar coatings fabricated on PS-b-PEO templated (A–E) PEEK, (F–J) CFPEEK, and (K–O) UHMWPE substrates. Columns correspond to different metal oxides: TiO₂, Al₂O₃, MgO, CaO, and Ag₂O (from left to right). Each image shows the resulting surface morphology following metal ion infiltration and UVO treatment, highlighting the variation in pattern formation across both substrate type and metal oxide composition.

Figure 7

Size distribution histograms for PEEK (A–F), CFPEEK (G–L), and UHMWPE (M–R) coated substrates. Columns represent different coatings: PS-b-PEO (A,G,M), Ag₂O (B,H,N), Al₂O₃ (C,I,O), MgO (D,J,P), CaO (E,K,Q), and TiO₂ (F,L,R). Histograms in panels A, G, and M correspond to the PS-b-PEO template before metal infiltration (presented in Figure 4), while the remaining histograms are derived from the SEM images shown in Figure 6. This figure enables an assessment of the pattern transfer fidelity from the BCP template to the final metal oxide nanostructures across different substrates and metal ions.

Figure 8

XPS fitted spectra for metal oxide nanopillar coatings on PS-b-PEO templated substrates: PEEK (A–E), CFPEEK (F–J), and UHMWPE (K–O). Columns correspond to different metal oxides: Ag₂O, Al₂O₃, MgO, CaO, and TiO₂ (left to right). Each spectrum confirms the chemical composition of the deposited nanopillars. Peaks were fitted based on reference binding energies to identify characteristic oxidation states.