Practicing the concept of “structuring” processing in the manufacture of polymer films

Polymer processing is a technology used to transfer raw materials into products with different shapes and functionalities and is a key step for polymer application. After years of development, the polymer processing task has changed from traditional processing, which mainly addresses the specific shapes of articles and focuses on the effect of processing on the structures and properties of polymers, to modern processing, which directly transforms a “designed structure” into commercial products via processing. It is the so-called “structuring” processing. Owing to the unique long-chain nature and slow topological relaxation, polymers are always driven and frozen into different nonequilibrium conformations, providing an effective way to design a given polymer material with desired structure and tunable performances via processing. Among the endless number of processing techniques, film casting is a prototypical pathway involving high supercooling or/and a strong flow field, based on which diverse thin polymer films have been successfully developed. In this review, taking isotactic polypropylene (iPP) film as an example, we highlight the strategy of “structuring” processing, in which we transform various crystalline structures of iPP into diverse commercial film products.