Dynamics of Star-Shaped Polystyrene Molecules: From Arm Retraction to Cooperativity

• DOI: 10.1021/acs.macromol.6b00456
• Publication Date: 2016-07-26T18:07:48Z
• Authors: Kyle J. Johnson; Emmanouil Glynos; Georgios Sakellariou; Peter Green
• Keywords: Cooperativity; Polystyrene; Star polymer; Star (game theory); Dynamics

The frequency ω dependent storage G′(ω) and loss G″(ω) moduli of star-shaped polystyrene (SPS) molecules a range functionalities f molecular weights per arm Ma were measured under small amplitude oscillatory shear conditions. Star-shaped macromolecules are composed an inner region, core, where the chain segments stretched "packing" density is higher than that outer corona. dependencies for low functionality (f < 8) with long arms well described by model Milner McLeish, indicating translational dynamics facilitated retraction mechanism. With increasing values decreasing fails—the process no longer valid—due largely to size core in relation overall molecule. exhibit evidence spatial structural order due entropic, intermolecular interactions, these occur via cooperative process, akin soft colloids, sufficiently large Ma. may be summarized diagram delineating different mechanisms facilitate flow as function