Calculations on trimodal elastomeric networks. Effects of chain length and composition on ultimate properties

Polymer networks having a bimodal distribution of network chain lengths can be prepared by end-linking two sets of chains having different molecular weights. These unusual elastomers frequently have better mechanical properties than those having a unimodal distribution, which suggests that trimodal distributions could possibly yield further improvements. The theory of bimodal networks based on chains with finite extensibility was therefore extended to trimodal networks. Specifically, networks having various compositions of very long, long, and short chains were characterized with regard to their toughness in elongation. The results showed that a trimodal network prepared by incorporating small numbers of very long chains into a bimodal network of long and short chains could have significantly improved ultimate properties.