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 (Tg), 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 Tg 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 Tg of the polymer is well below 0 °C. Smaller polar groups tend to show a smaller increase in Tg, and an increased linker length helps to decreases Tg, which is generally favorable for high permittivity. Our findings guided us to design polysiloxanes with a permittivity as high as 27.7 and a Tg of −18.2 °C. To the best of our knowledge, this is the highest dielectric permittivity of a polymer with a Tg well below room temperature.