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Smart materials: Metal cations-recognizable thermoresponsive polymers

Date:
October 14, 2022
Source:
Osaka Metropolitan University
Summary:
Scientists have created a novel thermoresponsive polymer by adding divalent cations to polymers and water solvents. They also succeeded in controlling thermoresponsive properties by changing the type and mixing ratio of ionic species. This new polymer type is expected to be applied as an analytical reagent for ion-sensing devices and as a material for drug delivery systems.
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Often referred to as smart materials, temperature-responsive or thermoresponsive polymers are gaining attention for their ability to respond to external temperature changes, allowing for an extensive range of applications. Making this smart material even smarter by improving the flexibility of its response to temperature, Osaka Metropolitan University scientists have developed a novel polymer, the thermoresponsiveness of which can easily be regulated by changing the type and mixing ratio of ionic species. Their findings were published in Macromolecules.

Polymers that exhibit temperature-related change in their physicochemical properties are called thermoresponsive polymers. They include two types: polymers with lower critical solution temperatures (LCST) and polymers with upper critical solution temperatures (UCST). Above a certain temperature, the former are insoluble, whereas the latter are soluble. In LCST-type thermoresponsive polymers, as the temperature increases, the polymer-solvent interaction decreases and the polymer-polymer interaction becomes dominant, leading to precipitation of polymers from the solvent. Conversely, in UCST-type thermoresponsive polymers, as the temperature increases, the polymer-polymer interaction decreases and the polymer-solvent interaction becomes dominant, resulting in dissolution. This indicates the affinity between the polymer and the solvent as an important factor in most thermoresponsive polymers.

Conventionally, the polymer-solvent interaction is used to regulate thermoresponsiveness in designing thermoresponsive polymers. However, attention has recently focused on a new technique that regulates thermoresponsiveness by adding a third component. This technique often uses organic solvents, but to develop materials such as those for drug delivery systems, it is necessary that water, which is harmless to the human body, be used as the solvent.

The research team led by Professor Atsushi Harada from the Graduate School of Engineering at Osaka Metropolitan University used water as the solvent and developed an LCST-type thermoresponsive polymer by adding alkaline earth metal ions -- which are divalent cations -- to polymers and aqueous solutions. They succeeded in regulating thermoresponsive properties, simply by changing the species and mixing ratio of the ions. This is different from the conventional technique that can only regulate thermoresponsiveness by changing the structure of the polymers.

"We have developed a novel polymer that exhibits thermoresponsiveness in the presence of certain ions," concluded Professor Harada. "We expect that it will be applied as an analytical reagent for metal ion-sensing devices and as a material for drug delivery systems."


Story Source:

Materials provided by Osaka Metropolitan University. Note: Content may be edited for style and length.


Journal Reference:

  1. Junya Emoto, Yukiya Kitayama, Atsushi Harada. Thermoresponsiveness of Carboxylated Polyallylamines Induced by Divalent Counterions as Ionic Effectors. Macromolecules, 2022; 55 (16): 7204 DOI: 10.1021/acs.macromol.2c00795

Cite This Page:

Osaka Metropolitan University. "Smart materials: Metal cations-recognizable thermoresponsive polymers." ScienceDaily. ScienceDaily, 14 October 2022. <www.sciencedaily.com/releases/2022/10/221014101322.htm>.
Osaka Metropolitan University. (2022, October 14). Smart materials: Metal cations-recognizable thermoresponsive polymers. ScienceDaily. Retrieved July 13, 2024 from www.sciencedaily.com/releases/2022/10/221014101322.htm
Osaka Metropolitan University. "Smart materials: Metal cations-recognizable thermoresponsive polymers." ScienceDaily. www.sciencedaily.com/releases/2022/10/221014101322.htm (accessed July 13, 2024).

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