The objective of this study is the thermoreversible crosslinking of maleated ethylene/propylene copolymer (MAn‐g‐EPM) using the equilibrium reaction with diols. Covalent hemi‐ester crosslinks are formed via the reaction of anhydrides with alcohols, while an equilibrium shift at elevated temperatures may result in their removal. High conversions to hemi‐ester are obtained at low temperatures in the presence of p‐toluenesulfonic acid, whereas conversions are low at high temperatures. The presence of microphase‐separated aggregates acting as physical crosslinks was demonstrated for MAn‐g‐EPM and all crosslinked materials. The covalent crosslinks were only formed within the aggregates, resulting in stronger aggregates that persisted to higher temperatures. The tensile strength and elasticity were significantly improved upon increasing level of crosslinking, whereas the type of diol has less influence. The covalently crosslinked MAn‐g‐EPM was reprocessable via compression molding at temperatures above 175 °C. Irreversible diester formation occurred for the longer diols, but did not prevent reprocessing, while short diols evaporated. Both effects lowered the level of crosslinking, resulting in significantly changed mechanical properties. The reprocessability does not originate from an equilibrium shift, but from a dynamic exchange between crosslinked and non‐crosslinked functional groups, which allows crosslinks to disconnect and the corresponding chain segments to diffuse between aggregates. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1810–1825, 2008

Maleated ethylene/propylene copolymers (MAn-g-EPM) were thermoreversibly cross-linked via a reaction with primary alkylamines of different length, either with an equimolar amount to obtain the amide−acid or with an excess to obtain the amide−salt, which was confirmed using Fourier transform infrared (FTIR) spectroscopy. Small-angle X-ray scattering (SAXS) experiments showed the presence of microphase-separated aggregates for both the starting MAn-g-EPM and all alkylamide−acids and −salts, which act as physical cross-links. The materials could easily be remolded at 80 °C into homogeneous films for several times without changes in the FTIR spectra, indicating that the (physical) cross-links are truly reversible. The tensile properties and elasticity were improved by converting MAn-g-EPM to the amide−acids due to hydrogen bonding and even further by converting the amide−acids to the amide−salts due to additional ionic interactions besides hydrogen bonding. Better tensile properties and elasticity were observed for the octadecylamine, which was explained by packing of the long alkyl tails in a crystalline-like order. Apparently, this packing is rather ill-defined, since a scattering peak could only be observed in the SAXS patterns of material modified with a large excess of octadecylamine after processing above 140 °C. Irreversible imide formation occurred for all amide−acids and amide−salts at high temperatures, resulting in disappearance of the aggregates and, hence, a dramatic decrease in mechanical properties. Therefore, these temperatures should be avoided during the (re)processing. Replacement of the excess of alkylamine with a different base, viz. potassium hydroxide, resulted in prevention of imide formation at high temperatures and a further improvement in mechanical properties.