Heat-sensitive polymers recognizable by metal cations — ScienceDaily

Often referred to as smart materials, temperature-sensitive or heat-sensitive polymers are attracting attention for their ability to respond to external temperature changes, enabling a wide range of applications. To make this smart material even smarter by improving the flexibility of its temperature response, scientists from Osaka Metropolitan University have developed a new polymer, whose thermoresponsiveness can easily be regulated by changing the type and mixing ratio. ionic species. Their findings were published in Macromolecules.

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

Classically, the polymer-solvent interaction is used to regulate thermosensitivity in the design of thermosensitive polymers. However, attention has recently turned to a new technique that regulates thermoreactivity 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, is used as the solvent.

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

“We have developed a new polymer that exhibits thermoreactivity in the presence of certain ions,” Professor Harada concluded. “We expect it to be applied as an analytical reagent for metal ion detection devices and as a material for drug delivery systems.”

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

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