Structure-property relationships in metallosupramolecular poly(p -xylylene)s

The self-assembly polymerization of ditopic monomers via metal-ligand binding is a facile route for the preparation of metallosupramolecular polymers. Here this approach was used for the synthesis of supramolecular poly(p-xylylene)s based on 2,6-bis(1′-methylbenzimidazolyl)pyridine (Mebip) end-capped telechelic oligomers with a p-xylylene core and different metal salts. These polymers can be readily processed from solution and merge the ease of processing of supramolecular materials with the good thermal stability of the p-xylylene core. The nature of the metal cation (Fe ²⁺, Zn ²⁺, La ³⁺) and counteranion (ClO ₄ ^-, OTf ^-, NTf ₂ ^-) was systematically varied, and a tetrafunctional supramolecular cross-linker was used to probe how these modifications influence the materials' properties. Interestingly, and in contrast to other metallosupramolecular polymers, where the nature of the metal salt plays a critical role, only minor property differences were observed for the materials studied. Instead, the properties of the supramolecular poly(p-xylylene)s investigated appear to be primarily governed by the crystalline nature of the telechelic oligomer. We note that minor impurities in the latter can exert a significant influence on the metallosupramolecular polymer's properties and report a new protocol for the synthesis and purification of Mebip-end-capped p-xylylene telechelic oligomers.