High entropy engineered polymer blends with enhanced dielectric properties and high temperature stability.

There is increasing need for higher performance dielectric polymers for devices in power conversion systems for renewable energy generation and electric vehicles. In particular, materials with higher dielectric permittivity, lower loss and the ability to operate at higher temperatures. We have developed a counter intuitive method to achieve this, the melt blending of multiple immiscible polymers, in an approach that mimics high entropy materials design. We demonstrate that using this approach we can significantly exceed the rule-of-mixtures for the dielectric constant (>250%), whilst surprisingly retaining a low loss tangent. The materials show increased thermal stability up to 150 °C, which opens up the possibility of the wider application of dielectric polymers. We provide a consistent model to describe the behaviour based on the use of polymers with different glass transition temperatures to frustrate the de-blending of the immiscible polymers during melt processing. This produces highly amorphous and disordered polymer blends with increased inter-chain spacing (free volume) and increased rotational freedom of the polar groups in polar nano regions. This approach has wide applicability to other polar polymer blends and is scalable.