ABSTRACT
This chapter discusses a brief description of the gradient-type theories of dielectrics with classical and non-classical kinematics. It provides the essentials of the micromorphic continuum theory of electroelastic dielectrics and explores the strain gradient theories of dielectrics and their application to the investigation of direct and converse flexoelectric effects. The goal of all generalized gradient-type theories of elastic media is to enclose the mechanical properties at a microscopic level into a macroscopic description. The nonlocal theory of dielectrics was used to explain a number of phenomena that cannot be justified by classical theories of electroelastic media. The mentioned gradient-type theories of dielectrics can be conventionally subdivided into two groups. One group of theories uses the classical kinematics. Another group of extended theories of dielectrics includes the theories that consider the additional degrees of freedom. The classical theory of elasticity envisions a solid body as a continuum of material points, each with infinitesimal size and no inner structure.
