Effects of fatty acids having different alkyl tail lengths on rigidness of the shell region surrounding an ionic core and mechanical properties of poly(ethylene-co-methacrylic acid) ionomer/fatty acid blends

Abstract Herein, we suggest the importance of the rigidness of the shell region surrounding the ionic core in controlling the tensile mechanical properties of sodium-neutralized poly(ethylene-co-methacrylic acid) (EMAA) ionomers blended with several fatty acids with different alkyl tail lengths. When dodecyl acid (DA) or lauric acid (LA) was blended, the local Tg of most of the shell region decreased to lower than room temperature, whereas the ionic core was still glassy at room temperature. However, the local Tg of the shell region was almost equal to room temperature when stearic acid or behenic acid was blended. The EMAA ionomers blended with DA and LA exhibited higher stretchability and toughness in the tensile test and shorter relaxation time in the stress–relaxation test than the other samples because some neutralized and/or unneutralized carboxy groups attached to highly stressed polyethylene chains detachfrom the ionic cores when the shell region was soft.