Decoupling the structural origins of strength and toughness in industrially relevant heterogeneous elastomers

Using coarse-grained molecular dynamics, we investigate the structure-property relationships for industrially relevant heterogeneous elastomer networks formed by random crosslinking. Our simulations reveal a clear decoupling of mechanical properties: strength and elongation are governed by the network's cycle rank (a measure of global topology), while toughness (fracture energy) is governed by the effective chain ratio and strand length uniformity. Notably, network uniformity, which is critical for toughness, is enhanced by using wider reactive site spacing and lower-functionality crosslinkers. This insight provides a rational design guideline to overcome the common strength-toughness trade-off by independently tuning molecular parameters to optimize distinct mechanical properties in these complex yet industrially vital materials.