Thickness Gradient in Polymer Coating by Reactive Layer-by-Layer Assembly on Solid Substrate

Area of Science:

• Polymer Science
• Materials Science
• Surface Chemistry

Background:

• Precise control over polymer coating thickness is crucial for advanced material applications.
• Gradient polymer coatings offer tunable surface properties but require robust fabrication methods.

Purpose of the Study:

• To develop and characterize a simple, robust methodology for creating nanometer-precision thickness gradients in polymer coatings.
• To investigate the influence of key parameters on gradient formation and analyze the resulting surface properties.

Main Methods:

• Reactive layer-by-layer assembly of polyester and polyethylenimine on gold substrates.
• Systematic variation of incubation time, polymer concentration, and substrate tilt angle.
• Characterization using atomic force microscopy (AFM), angle-dependent infrared spectroscopy, and fluorescence microscopy.

Main Results:

• Achieved thickness gradients ranging from 0-20 nm with nanometer precision.
• Demonstrated decreasing surface roughness with increasing coating thickness.
• Observed an increase in Young's modulus (0.50 to 1.4 MPa) with greater thickness, indicating enhanced mechanical stability.
• Determined polymer orientation using infrared spectroscopy and correlated fluorescence intensity with coating thickness.

Conclusions:

• The developed methodology offers precise control over polymer coating thickness gradients.
• The fabrication process is robust and relies on fast reaction kinetics for efficient layer deposition.
• The characterized gradient coatings exhibit tunable nanomechanical and surface properties, suitable for various applications.