Threading Polystyrene Stars: Impact of Star to POM‐POM and Barbwire Topology on Melt Rheological and Foaming Properties

Abstract

AbstractPolymer topology highly impacts rheological melt and foaming properties. Grafting sidechains onto a linear polymer typically results in shear thinning and strain hardening in elongation flow. To study the influence of an increasing number of covalently connected polystyrene (PS) starsswith a linear PS chain (Mw,PS= 90 kg mol−1), low‐disperse branched polymers withsranging from one to four are synthesized. Each star contains approximately 12 sidechains with a length ofMw,a≈ 25 kg mol−1. Oscillatory shear measurements indicated that the zero‐shear viscosityη0scales withη0 ≈ atTref= 180 °C. Moreover, uniaxial elongation rheology allows determining the strain hardening factorSHF, which varies betweenSHF= 2–135, with increasings. Foaming experiments revealed that combining viscosity reduction with the improvement of stretchability promotes higher volume expansion ratios (VER= 3.21–10.41) and the formation of larger cells (D= 4.8–14.8 µm).