ABSTRACT
Thermoreversible cross-linking polymers are designed based on reversible cross-linking bonds. These bonds are able to reversibly dissociate and associate upon the input of external energy, such as heat or light. Reprocessibility is possible for this kind of material. The objective was to thermoreversibly cross-link maleic anhydride grafted chlorobutyl rubber (MAH-g-CIIR) via a reaction with octadecylamine, with an excess to obtain amide-salts, which form both hydrogen bonds and ionic interactions. X-ray diffraction experiments showed the presence of microphase-separated aggregates that acted as physical cross-links for both the MAH-g-CIIR precursor and amide-salts. The tensile properties were improved by converting MAH-g-CIIR to amide-salts, because of the combination of hydrogen bonding and ionic interactions. The cross-linked materials could be repeatedly compression molded at 155 °C into homogeneous films. The differential scanning calorimetry curves and Fourier transform infrared spectra indicate that hydrogen bonds are of a thermoreversible nature, but the recovery of ionic bonds is impossible. After treatment with heating-cooling for up to three cycles, the tensile strength of the thermoreversible cross-linking CIIR was greatly reduced. The gradual reduction in the effectiveness of the ionic-hydrogen bonds is the major contribution to the reprocessibility of these materials.
