2023-08-01 22:10:00
While many absorbent materials lose their ability to hold water as temperature increases, MIT engineers discovered a material that resists this rule. Polyethylene glycol (PEG), a hydrogel material commonly used in cosmetics or industrial coatings, manages to absorb moisture from the atmosphere even when temperatures rise.
The engineers of WITH found that PEG doubles its water absorption when the temperature goes from 25 to 50°C. This is explained by a heat-triggered transformation. The hydrogel’s microstructure changes from a crystalline phase to a less structured “amorphous” phase, which reinforces its ability to capture water.
Potential uses
Thanks to these particularities, the researchers have developed a model capable of guiding the creation of other heat-resistant absorbent materials. They imagine that these might be used to harvest humidity from the air and produce drinking waterespecially in desert regions.
The materials might also be integrated into heat pumps and air conditioners to more effectively regulate temperature and humidity.
New way of research
The researchers found that the PEG has a melting point naturally located around 50°C. At this temperature, its microscopic structure, normally crystalline, completely decomposes and transforms into an amorphous phase.
This transformation provides more opportunities for the polymers in the material to capture fast moving water molecules.
“Other polymers might in theory exhibit this same behavior, if we manage to change their melting points within a given temperature range.“, explains Shaoting Lin, a member of the team.
Now that the group has come up with a theory, they plan to use it as a model for designing materials specifically to capture water at higher temperatures.
“We want to customize our design to ensure that a material can absorb a relatively large amount of water, low humidity and high temperature“, explained M. Liu. “It might then be used for the collection of atmospheric water, in order to bring drinking water to people living in hot and arid environments.“
Synthetic
The discovery of the unique behavior of PEG opens new perspectives for the use of hydrogels and the engineering of absorbent materials. The next steps the researchers plan are to use their new theory as a blueprint for designing materials specifically for capturing water under high-temperature conditions.
For a better understanding
What is the transformation phase?
The transformation phase is a process in which a material changes its structure, which often affects its physical and chemical characteristics. In this case, the transformation within the PEG allows this material to increase its water absorption capacity.
When does the transformation phase occur within the PEG?
The crystal-amorphous transformation occurs when PEG reaches a temperature of 50 degrees Celsius, which is its melting point. During this transition phase, the material offers more attraction sites for water, which improves its ability to absorb.
What are the potential applications for PEG?
Generally used in cosmetics, industrial coatings and pharmaceutical capsules, PEG offers new perspectives. Its ability to absorb moisture at high temperatures might be exploited to produce drinking water in arid regions. Additionally, the materials might be used in heating and air conditioning systems to regulate temperature and humidity levels.
This research was supported in part by the Office of Energy Efficiency and Renewable Energy of the US Department of Energy.
MIT engineers have discovered that a common hydrogel has unique superabsorbing abilities. Even as temperatures soar, the transparent material continues to absorb moisture and might serve to harvest water in desert regions and passively regulate humidity in tropical climates. Picture: Felice Frankel
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