Some Comments on the Paper of Larsen et al. and the Nature of Cross-Linking in Coal

In this short paper two arguments are made. First, the swelling reported in the preceding paper cannot be due to a selective titration of hydrogen-bonding cross-links, for various reasons associated with the thermodynamics and statistical mechanics of how these interactions are treated. Second, in the “liquid” state (i.e., T > T g ) H bonds cannot be cross-links because their “lifetimes” or relaxation times are much shorter than that of a mechanical experiment such as swelling. In other words, hydrogen bonds break and re-form many times during the course of swelling, giving the chain segments ample time and opportunity to relax.