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The conformal nanoporous inorganic coatings with accessible pores that are stable under applied thermal and mechanical stresses represent an important class of materials used in the design of sensors, optical coatings, and biomedical systems. Here, we synthesize porous AlOx and ZnO coatings by the sequential infiltration synthesis (SIS) of two types of polymers that enable the design of porous conformal coatings—polymers of intrinsic microporosity (PIM) and block co-polymer (BCP) templates. Using quartz crystal microbalance (QCM), we show that alumina precursors infiltrate both polymer templates four times more efficiently than zinc oxide precursors. Using the quartz crystal microbalance (QCM) technique, we provide a comprehensive study on the room temperature accessibility to water and ethanol of pores in block copolymers (BCPs) and porous polymer templates using polystyrene-block-poly-4-vinyl pyridine (PS75-b-P4VP25) and polymers of intrinsic microporosity (PIM-1), polymer templates modified by swelling, and porous inorganic coatings such as AlOx and ZnO synthesized by SIS using such templates. Importantly, we demonstrate that no structural damage occurs in inorganic nanoporous AlOx and ZnO coatings synthesized via infiltration of the polymer templates during the water freezing/melting cycling tests, suggesting excellent mechanical stability of the coatings, even though the hardness of the inorganic nanoporous coating is affected by the polymer and precursor selections. We show that the hardness of the coatings is further improved by their annealing at 900 °C for 1 h, though for all the cases except ZnO obtained using the BCP template, this annealing has a negligible effect on the porosity of the material, as is confirmed by the consistency in the optical characteristics. These findings unravel new potential for the materials being used across various environment and temperature conditions.
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Polycaprolactone - based block copolymers for nanopatterning oxide materials via sequential infiltration synthesis
Abstract Sequential infiltration synthesis (SIS) has emerged as a powerful technique to integrate inorganic materials into polymeric templates for fabricating functional hybrid and inorganic-only nanostructures. While several polymers, including self-assembled block copolymers (BCPs), have been widely used as templates for inorganic and hybrid oxide nanostructures, biocompatible polymers such as polycaprolactone (PCL) have not been explored for nanopatterning. In this work, we investigate SIS in polystyrene-block-polycaprolactone (PS-b-PCL) BCPs to demonstrate the feasibility of PCL as a guiding polymer for selective infiltration of Al₂O₃. Fourier transform infrared spectroscopy (FTIR) confirmed the strong interaction of TMA–H₂O precursors with the oxygen-containing functional groups of PCL, while scanning electron microscopy (SEM) revealed well-defined Al₂O₃ nanostructures after SIS and polymer removal. By varying the number of SIS cycles and processing temperatures, we observed systematic changes in the inorganic content and nanostructural fidelity, highlighting the tunability of the process. Notably, significant Al₂O₃ incorporation occurred during the first SIS cycle due to strong PCL–precursor interactions, even at temperatures as low as 60 °C, making the process both cost-effective and precise. These findings demonstrate that PCL is a promising guiding polymer for SIS, with potential to extend beyond conventional systems such as polymethylmethacrylate (PMMA). This work opens new opportunities for fabricating oxide nanostructures with applications in nanopatterning, dielectric coatings, and bio-related nanomaterials.
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- PAR ID:
- 10642180
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Nanotechnology
- ISSN:
- 0957-4484
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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