Controlled growth of layer-by-layer assembled polyelectrolyte multilayer films under high electric fields

Area of Science:

• Materials Science
• Surface Chemistry
• Electrochemistry

Background:

• Layer-by-layer (LBL) growth of polyelectrolyte multilayers (PEM) is typically controlled using chemical methods.
• External electric fields (E-Fields) have been explored for PEM control, but often involve water hydrolysis at electrodes.
• Isolating electrodes could enable direct E-Field control over polyelectrolyte conformation in solution.

Purpose of the Study:

• To investigate the non-chemical control of LBL growth using E-Fields by isolating electrodes from water.
• To determine if E-Fields can influence polyelectrolyte conformation in the solution phase for LBL assembly.
• To establish a novel method for controlling PEM growth without chemical additives.

Main Methods:

• Utilized attenuated total reflectance infrared spectroscopy (ATR-IR) to monitor adsorption kinetics.
• Sequentially adsorbed polyacrylic acid (PAA) and polydiallyldimethylammonium chloride (PDADMAC) onto a TiO2 film.
• Applied an external E-Field, varying its direction relative to the substrate, during the LBL assembly process.

Main Results:

• The direction of the applied E-Field significantly controlled PEM growth dynamics.
• Observed non-linear growth or decay in adsorbate mass depending on E-Field orientation.
• Identified conditions leading to a decrease in successive layer mass, resulting in a cessation of growth.

Conclusions:

• E-Field orientation is a critical parameter for controlling LBL assembly of PEMs.
• Non-chemical control of PEM growth is achievable by manipulating polyelectrolyte conformation via isolated E-Fields.
• This method offers a new pathway for precise fabrication of functional multilayer films.