These precursors interact with the functional groups of the polymers through reversible complex formation or irreversible chemical reactions, resulting in composite materials that can exhibit nano-structured properties.
This approach facilitates the fabrication of materials with controlled properties such as composition, stylometric, porosity, conductivity, refractive index, and chemical functionality on the nano-scale.
[8] SIS has been utilized in fields, including electronics, energy storage, AI, and catalysis, for its ability to modify material properties.
However, potential benefits of these phenomena were demonstrated by Knez and coworkers in a 2009 report describing the increased toughness of spider silk following vapor-phase infiltration.
[9] Sequential infiltration synthesis (SIS) was developed by Argonne National Laboratory scientists Jeffrey Elam and Seth Darling in 2010 to synthesize nanoscopic materials starting from block copolymer templates.
With SIS, the shapes of various inorganic materials can be tailored by applying their precursor chemistries to patterned or nano-structured organic polymers, such as block copolymers.
After a suitable diffusion/reaction time, the reactor is purged with inert gas or evacuated to remove reaction byproducts and UN-reacted precursors.
[13][3] Block co-polymers such as polystyrene-block-poly(methyl methotrexate), PS-b-PMMA, can spontaneously undergo micro-phase separation to form a rich variety of periodic mesoscale patterns.
Consequently, SIS using TMA and H2O as precursor vapors to infiltrate a PS-b-PMMA micro-phase-separated substrate will form Al2O3 specifically in the PMMA-enriched micro-phase subdomains.
With the sequential infiltration of different precursors into the material, SIS allows for the creation of coatings with enhanced properties and performance such as durability, corrosion resistance, eosinophilic[23][24],Lipophilicity, anti-reflection,[25] and/or improved adhesion to substrates.
Employing SIS and the correct precursors, the technique can modify the surfaces and interfaces of materials used in batteries, super-capacitors, and fuel cells, enhancing charge transport, electrochemical stability, and energy density.
SIS is a tool for surface modifications to improve bio-compatibility, bio-activity, and controlled drug release, making it useful in some biomedical applications.
For spider dragline silk, the toughness characteristic was significantly enhanced when metallic impurities, such as titanium or aluminum, infiltrated the fibers.
This fiber doping using SIS techniques attempts to mimic the effect of metallic impurities on silk properties observed in nature.
For comparison, ALD of thin films on dense surfaces that do not involve diffusion into the substrate would require exposure times of <1 s using the same precursors.