LAUSR

Electrospun polymer core–shell fibers have gained much attention because of their promising applications in areas such as electronic devices, drug delivery, and tissue engineering. The morphology transformation of polymer core–shell fibers, however, has been rarely investigated. Here, we study the effect of thermal annealing on the morphology transformation of electrospun polystyrene (PS)/poly(methyl methacrylate) (PMMA) core–shell fibers on PMMA films. Two types of transformation processes are discovered. In the first type of the transformation process (type I), the PS cores transform to hemispherical particles after the annealing process; in the second type of the transformation process (type II), the PS cores transform to spherical particles after the annealing process. The measured sizes of the hemispherical and spherical PS domains fall into two classified regions, as predicted for the two different types of transformation processes. It is also observed that the growth rates of the undulated amplitud...