Polysiloxanes Modified with Different Types and Contents of Polar Groups: Synthesis, Structure, and Thermal and Dielectric Properties

Polymers with high dielectric permittivity are promising for the construction of next-generation transducers and energy storage devices with improved energy density. Here, we report the synthesis, glass-transition temperature ( T g ), and dielectric properties of polysiloxanes with different polarities. For this, we set out from poly(dimethyl- co -methylvinyl)siloxanes with different vinyl group content. The vinyl groups were then transformed into polar groups of various nature by an efficient one-step thiol–ene addition postpolymerization modification. We used the resulting collection of materials to establish structure–property relationships, side group design, and thermal and dielectric properties. Our results show that the T g increases with the polar group content and the strength of the polar group. A similar trend is observed for the dielectric permittivity as long as the T g of the polymer is well below 0 °C. Smaller polar groups tend to show a smaller increase in T g, and an increased linker length helps to decreases T g, which is generally favorable for high permittivity. Our findings guided us to design polysiloxanes with a permittivity as high as 27.7 and a T g of −18.2 °C. To the best of our knowledge, this is the highest dielectric permittivity of a polymer with a T g well below room temperature.