Ultrathin self-healing polymers create new, sustainable water-resistant coatings

Date:
September 16, 2021
Source:
University of Illinois at Urbana-Champaign, News Bureau
Summary:
Researchers have found a way to make ultrathin surface coatings
robust enough to survive scratches and dings. The new material,
developed by merging thin-film and self-healing technologies,
has an almost endless list of potential applications, including
self-cleaning, anti-icing, anti-fogging, anti-bacterial,
anti-fouling and enhanced heat exchange coatings, researchers said.



FULL STORY ========================================================================== Researchers have found a way to make ultrathin surface coatings robust
enough to survive scratches and dings. The new material, developed by
merging thin- film and self-healing technologies, has an almost endless
list of potential applications, including self-cleaning, anti-icing, anti-fogging, anti- bacterial, anti-fouling and enhanced heat exchange coatings, researchers said.


==========================================================================
The new study found that the rapid evaporative qualities of a specialized polymer containing a network of dynamic bonds in its backbone help form
a water-resistant, self-healing coating of nanoscale thicknesses. The
study, led by University of Illinois Urbana-Champaign mechanical science
and engineering professor Nenad Miljkovic and materials science and
engineering professor Christopher Evans, is published in the journal
Nature Communications.

For this study, the Miljkovic group's primary focus was on boosting
the efficiency of steam power plants, which are the biggest producers
of electricity globally, by using these types of coatings in their
condensers.

"The coatings, when applied to the surfaces of the condensers, make
them more water-resistant and efficient at forming water droplets, which optimizes heat transfer," said graduate research assistant Jingcheng Ma,
a co-lead author of the study.

When used in steam power plants, thin coatings can run into a multitude
of durability problems, the researchers said. Coatings can break
down in weeks, sometimes even hours. Such a short lifetime makes the
real-world application of the coatings impractical, which has been a foundational challenge in mechanical and materials sciences for about
eight decades. Thicker coatings can be more durable, but they reduce
heat transfer and erode the associated benefit of the coating.

Previous studies have shown that most ultrathin coatings develop tiny
pinhole defects once they cure onto a surface. Steam penetrates through
these defects, leading to the gradual delamination of the coating,
the researchers said, so their goal was to develop a pinhole-free, water-resistant thin-film and enhance the overall energy efficiency of
steam power plants by several percent.

"Self-healing materials can recycle and reprocess themselves," Evans
said. "We found that we can successfully utilize the healing enabled
by the dynamic bonds, allowing the coatings to self-repair in response
to scratching or to prevent pinholes from growing." Called dyn-PDMS,
the material can be easily dip-coated onto materials in nanoscale layers
on various surfaces like silicon, aluminum, copper or steel.

"One of the reasons we can get such thin layers is because the solvents
used in the reaction evaporate very quickly, leaving only the polymer,"
Evans said.

"Also, once cured, the material repairs itself from scratches very
fast -- so fast that it is difficult to observe in real time. We do
not see this behavior in large, bulk samples of the material -- only
in the thin-film, and that is a question we are trying to answer now."
The researchers posit that the ultrathin coatings developed in this study
offer a solution for sustainable water-resistant materials and raise
open scientific questions within materials science and fluid mechanics
that remain unanswered.

The Office of Naval Research, the International Institute for Carbon
Neutral Energy Research, the Air Force Office of Scientific Research
and the National Science Foundation supported this research.

Miljkovic and Evans are both affiliated with the Materials Research
Laboratory.

Miljkovic also is affiliated with electrical and computer
engineering. Evans also is affiliated with the Beckman Institute for
Advanced Science and Technology and chemical and biomolecular engineering.

========================================================================== Story Source: Materials provided by University_of_Illinois_at_Urbana-Champaign,_News_Bureau.

Original written by Lois Yoksoulian. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Jingcheng Ma, Laura E. Porath, Md Farhadul Haque, Soumyadip Sett,
Kazi
Fazle Rabbi, SungWoo Nam, Nenad Miljkovic, Christopher
M. Evans. Ultra- thin self-healing vitrimer coatings for
durable hydrophobicity. Nature Communications, 2021; 12 (1) DOI:
10.1038/s41467-021-25508-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210916124026.htm

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