Molecular origin of the foam structure in model linear and comb polystyrenes: I. Cell density

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

“…In this respect, the results are also consistent with findings by Abbasi et al. [ 18,23 ] who showed at the example of comb PS290‐ N br ‐44 series, that the highest density of LCB, e.g., N br = 190 with bottlebrush‐like side chain crowding, did not achieve the highest SHF. Consequently, this particular comb PS also performed worse in foaming when it comes to achieving low dense foams.…”

“…This tremendous effect of branching on the SHF of comb PS has so far only been reported by Abbasi et al. [ 18,20,23 ] for a LCB comb PS290‐120‐44 with well‐entangled side chains of 44 kg mol −1 and similar backbone length and branching number, however, at much lower strain rates of 0.1 s −1 . In comparison with the newly synthesized comb PS310‐100‐40 possessing similar structural features, the results are consistent as both LCB combs show their maximum SHF at the same rate of 0.1 s −1 .…”

“…Thus, on the basis of a similar set of molecular parameters in previous LCB comb PS, the number of entanglements of the backbone segments between two branch points, Z s ≈ 0.2, was presumed to be optimal for high SHF and VER. [ 23 ] Details of the synthesis of comb PS and purification by precipitation fractionation method have already been presented in previous publications. [ 18,38 ] LCB comb PS310‐100‐40 was used as the precursor for the next branching generation and the cycle of functionalization and grafting‐onto step was repeated to achieve bob PS, as schematically illustrated in Figure .…”

Sustainable Synthesis of Non‐Isocyanate Polyurethanes Based on Renewable 2,3‐Butanediol

“…[ 42 ] The cell stability during expansion can be enhanced by using a polymer that shows strain hardening, since the polymer melt becomes more stretchable and thus, prevents the cells from rupture and coalescence compared to a polymer without any strain hardening behavior. [ 43 ]…”

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

“…Materials combining strain hardening in elongational flow at $$\dot \varepsilon $$ = 10–1 s −1 with a low η 0 in shear are highly suitable for foaming polymers, as they support foamability by reducing cell coalescence and rupture. [ 41–45 ] The presented series meets both criteria, hence, we tested the samples regarding their foaming behavior.…”