Polymer crystallization studied by hyphenated rheology techniques: rheo-nmr, rheo-saxs, and rheo-microscopy

Abstract

Rheological set-ups with in situ analytical sensors, combine information on the flow and deformation behavior of soft matter, with simultaneous insights into structural and dynamic features. Furthermore, they permit the study of soft matter under well-defined flow conditions. Herein are presented hyphenations of rheology and nuclear magnetic resonance (NMR), small angle X-ray scattering (SAXS), and optical microscopy. They are employed to unravel relationships between the molecular dynamics, morphology, and rheology of crystallizing polymers. The results confirm a physical gelation process during polymer crystallization, mediated by the interaction of growing superstructures at volume fractions of 10–15%. The buildup of row-nucleated structures during flow-induced crystallization is found to reduce the time of gelation as detected by the rheological response. These investigations help to clarify the crystallization mechanism, structure–property relationships, and the hardening behavior of crystallizing polymers.