Using a hydroxy-functionalized terpyridine as initiator, a poly(epsilon-caprolactone) containing one terpyridine endgroup was prepared by tin octanoate-catalyzed controlled ring-opening polymerization. The omega-hydroxy group of this polymer was subsequently reacted with an isocyanato-ureidopyrimidinone, resulting for the first time in polymers bearing a metal-coordinating ligand on the one and a hydrogen-bonding unit on the other chain end. Hydrogen-bonded supramolecular dimers were shown to be present in chloroform solution. The subsequent addition of iron(II) ions resulted in the formation of high molecular weight supramolecular polymers with novel properties resulting from the combination of both types of noncovalent interactions in the main chain, as could be shown using capillary viscosimetry and rheometry.

The microphase structure of ionomers based on an amorphous, maleated ethylene-propylene copolymer was investigated by using small-angle X-ray scattering (SAXS) and solid-state NMR experiments. It was shown that in this kind of ionomers grafted maleic anhydride, its salts with Zn 2+ and a fraction of EPM chain fragments form immobilized, ion-rich aggregates. Three types of EPM chain units with different mobility were detected in the ionomers and in the ionomer precursor, which can be attributed to chain units with low mobility forming aggregates surrounded by an interfacial layer, EPM network chains interconnecting these aggregates, and network imperfections such as dangling ends and chain loops. When the the degree of neutralization is increased, the average dimension of the immobilized aggregate remains almost constant, while the thickness of the interfacial layer with restricted mobility slightly increases. The size of the aggregates in MAn-g-EPM ionomers is significantly larger compared to other ionomers, and as a consequence, the number of acid groups within an aggregate is also larger. At 50% neutralization, the number of aggregates suddenly decreases. The changes in some macroscopic properties, such as compression set and tensile properties, are related to the morphology of the ionomers as determined by SAXS and NMR. When the degree of neutralization is increased, the properties of the materials change due to strengthening of the ionic aggregates.

The thermoreversible nature of the ionic associations in aggregates makes ionomers with a low glass transition temperature interesting candidates for thermoplastic elastomers. In this paper, a low-T g ionomer based on low molecular weight ethylene−propylene copolymers modified by maleic anhydride (MAn-g-EPM) is introduced, and the morphology of a series of ionomers, neutralized with Cs+, Na+, K+, Li+, Zn2+, Ba2+, and Mg2+, was investigated with small-angle X-ray scattering (SAXS). To determine the size and composition of the ionic aggregates, the observed SAXS peak was interpreted with the help of the Yarusso−Cooper model, which describes the ionomer morphology by spherical aggregates of the ionic species with a high electron density surrounded by a layer with a restricted mobility. The results from the ionomer precursors suggest that there is a critical concentration above which aggregation of the polar groups in the apolar matrix occurs. Upon increasing degree of neutralization, the average dimension of the aggregate remains almost constant, while the restricted mobility layer increases. The size of the aggregates is much larger in comparison to other ionomer systems, and as a consequence, the number of acid groups within an aggregate is much larger. For low degrees of neutralization, it was shown that the aggregates contain a large fraction of EPM fragments of at least 60 vol %. For the ionomers neutralized with divalent cations, it was observed that the morphology changes drastically beyond degrees of neutralization of 50%; the number of the aggregates decreases, and the size increases. This was explained with the help of the coordination mechanism.

X-ray absorption spectroscopy (EXAFS) was used to characterize zinc-neutralized ionomers made from ethylene−propylene copolymers with grafted maleic anhydride units (Zn-MAn-g-EPM). The structure of the zinc moieties in the dry system consisted of two chelating carboxylate groups around one zinc atoma structure much different than if the carboxylate anions come from acrylic or methacrylic acid. These self-contained zinc−two chelating carboxylate structures assemble into a larger superstructure as shown in a previous SAXS study, which indicated that the microphase-separated ionic aggregates are ∼2 nm. This superstructure must therefore contain significant amounts of nonionic material, consistent with the observation that the superstructure also forms in the unneutralized maleic anhydride precursor. After addition of water, zinc atoms in the sample with 10% of the carboxylate groups neutralized were fully solvated, i.e., zinc was surrounded by six water molecules. Zinc atoms in samples with higher neutralization levels had two carboxylate oxygens replaced by water oxygens, which in turn maintained the zinc coordination number at four.

No abstract