Comb and Branch‐on‐Branch Model Polystyrenes with Exceptionally High Strain Hardening Factor SHF > 1000 and Their Impact on Physical Foaming

The influence of topology on the strain hardening in uniaxial elongation is investigated using monodisperse comb and dendrigraft model polystyrenes (PS) synthesized via living anionic polymerization. A backbone with a molecular weight Mw,bb = 310 kg mol−1 used for all materials, while number 100 short (SCB, Mw,scb 15 mol−1) or long chain branches (LCB, Mw,lcb 40 are grafted onto backbone. LCB serves as precursor dendrigraft-type branch-on-branch (bob) structures to add second generation ≈ 14 that varied from 120 460. SCB combs achieve remarkable factors (SHF) around 200 at rates greater than 0.1 s−1. In contrast, bob PS reach exceptionally high SHF 1750 very low 0.005 s−1 tilted sample placement extend maximum Hencky 4 6. To best authors’ knowledge, this have never been reported polymer melts. Furthermore, batch foaming CO2 volume expansions resulting foams correlated elongational properties.