LAUSR

Application of ionomers is often disturbed by their brittleness originating from limited stretchability of the network strands physically cross-linked by the ionic sites therein. Thus, an effective method of improving the ductility is to increase the length of network strands (and/or entanglements). Considering this point, this study examined linear viscoelasticity (LVE) and nonlinear elongational rheology of unentangled copolymers of hexyl methacrylate (HMA) and the ionic monomer sodium 4-vinylbenzenesulfonate hydrate (SSNa). The ionized SSNa monomer, being randomly distributed along the chain backbone at a concentration ranging from <1 to ∼4 monomers per chain, served as the physical cross-link (or physical branching point). The LVE data showed a sol-to-gel transition, and the ductility of the sample turns out to be strongly related to the degree of gelation. Analysis of those data gave an average length of the network strands, and the ductility of the ionomer samples detected in the nonlinear elongatio...