How to Choose a Secondary Interaction to Improve Stretchability of Associative Polymers?
Huanhuan Yang, Shilong Wu, Quan Chen
Abstract
This study focuses on the stretchability of brittle ionomers after introducing three types of hydrogen bonds, i.e., dual, triple, and quadruple hydrogen bonds. The introduction of dual or triple hydrogen bonds that are weaker than the ionic association improves the stretchability, and better improvement has been achieved for the triple hydrogen bonds. In comparison, the introduction of quadruple hydrogen bonds that are equally strong as the ionic association does not show this type of improvement. This result strongly indicates that there is an optimized strength ratio between the first (the stronger ionic) network and the secondary (the weaker hydrogen-bonding) network, i.e., the secondary network should be considerably weaker but still not too weaker than the first network. When this condition is satisfied, continuous dissociation and association of the secondary network weaken the chain retraction after the strain-induced breakup of the first network, thereby suppressing the formation of defects or microscopic cracks that potentially grow into the macroscopic fracture.