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Published on: August 28, 2014
Humidity-Controlled Growth of Self-Healing Poly(ethylenimine)/Poly(acrylic Acid) (PEI/PAA) Multilayer Films.
Shirley M V da R Hossack1, Jonathas P Siqueira1, Giovanni Budroni Netto1
1Institute of Physics Gleb Wataghin - UNICAMP, Campinas, São Paulo 13083-510 Brazil.
ACS Applied Polymer Materials
|June 19, 2026
Summary
Controlling humidity during the deposition of Poly-(ethylenimine)/poly-(acrylic acid) (PEI/PAA) layer-by-layer (LbL) films tunes their electrical properties, surface characteristics, and self-healing (SH) capabilities. Higher humidity enhances SH performance and dielectric response.
Area of Science:
- Materials Science
- Polymer Chemistry
- Nanotechnology
Background:
- Functional polymer coatings are crucial for organic electronics, sensing, and protective layers, demanding durability and self-healing (SH) properties.
- Poly-(ethylenimine)/poly-(acrylic acid) (PEI/PAA) layer-by-layer (LbL) films offer intrinsic SH ability, with properties significantly affected by retained water content during formation.
Purpose of the Study:
- To investigate the influence of controlled relative humidity (RH) on the formation and performance of PEI/PAA LbL films.
- To elucidate the role of water content in dictating the electrical, surface, and self-healing properties of these multilayers.
Main Methods:
- Fabrication of PEI/PAA LbL films at three controlled relative humidity levels (50%, 70%, 90%).
- Characterization using capacitance measurements, electrical transport analysis, terahertz time-domain spectroscopy (THz-TDS), and surface analysis (roughness, contact angle).
- Evaluation of self-healing capabilities under different humidity conditions.
Main Results:
- Film capacitance increased significantly with humidity, from 0.70 nF (70% RH) to 5 nF (90% RH).
- Negative differential resistance (NDR) behavior was observed, most pronounced in the 90% RH film.
- THz-TDS confirmed hydration differences via dielectric constant and refractive index changes.
- Surface roughness and hydrophobicity increased with RH, and only the 90% RH film showed complete self-healing within 10 minutes.
Conclusions:
- Humidity-controlled deposition is a scalable method to tune dielectric response, surface functionality, and SH performance in PEI/PAA LbL films.
- This control facilitates the development of reproducible, multifunctional coatings for advanced soft-electronic and sensing applications.
- Water content is a critical factor in optimizing the performance of these polyelectrolyte multilayers.
