Spiropyran-based supramolecular elastomers with tuneable mechanical properties and switchable dielectric permittivity

Area of Science:

• Polymer Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Silicone elastomers are versatile materials requiring adaptable properties for broad applications.
• Developing silicones with tunable or switchable characteristics is crucial for expanding their utility.
• Metallo-supramolecular chemistry offers a promising route to engineer such advanced polymer systems.

Purpose of the Study:

• To synthesize novel metallo-supramolecular polysiloxanes with easily tunable properties.
• To investigate the influence of zinc chloride (ZnCl2) concentration on material characteristics.
• To explore the potential of spiropyran as a molecular switch and cross-linker.

Main Methods:

• Synthesis of poly(dimethylsiloxane-co-3-aminopropylmethylsiloxane) reacted with epoxy-modified spiropyran (SP) in the presence of ZnCl2.
• Characterization using Differential Scanning Calorimetry (DSC), tensile testing, and Dynamic Mechanical Analysis (DMA).
• Investigation of molecular switching via UV-Vis spectroscopy and dielectric permittivity measurements.

Main Results:

• ZnCl2 facilitated the formation of metallo-supramolecular polymers with tunable mechanical properties.
• Spiropyran acted as both a physical cross-linker and a molecular switch.
• Dielectric permittivity was modulated by light exposure (UV/visible) depending on ZnCl2 content.
• Materials exhibited thermoplastic elastomer-like reprocessing and controllable solubility.

Conclusions:

• Metallo-supramolecular polysiloxanes offer a viable platform for creating silicone materials with switchable thermal, mechanical, and dielectric properties.
• The concentration of ZnCl2 is a key factor in controlling material properties and responsiveness.
• These tunable silicone elastomers hold potential for advanced applications requiring adaptable functionalities and reprocessing capabilities.