Control of the hierarchical structure of polymer articles via “structuring” processing

Every day, numerous polymer materials are fabricated into specific articles with definite sizes, shapes and forms using polymer processing. Obviously, polymer processing has become one of the most active areas of polymer science and engineering. The key is to profoundly explore the processing-structure-performance relations for various polymer-based materials. From a structure-dominated performance point of view, the ultimate physical/chemical properties of polymer articles are directly related to their internal multiscale (hierarchical) structures, which range from the molecular, nanometer, submicron and micron scale to the mesoscopic level. Because the features of hierarchical structures strongly depend on the external fields that are imposed during processing, many structural items, such as the chain configuration, crystalline polymorphism, orientation and phase separation behavior, can be well or precisely controlled, resulting in significant variations in the hierarchical structure. Due to developments in mechanical techniques, various external fields, such as thermal, shear, extension, ultrasonic, electronic, magnetic and super-critical fluid fields, may be introduced into polymer processing, leading to significant improvements in the tailoring of the microstructure/morphology via processing. This process is characterized by an “externally applied field determined hierarchical structure”, i.e., a “structuring” processing, which represents an advanced trend in modern polymer processing and is the topic of this review. This contribution includes the following: (1) an introduction, (2) the in situ monitoring of polymer processing, (3) progress in “structuring” processing and (4) concluding remarks and perspectives.