Toward Rehealable Supramolecular Polymers Using Aromatic Amide Motifs

摘要

Supramolecular polymerization and the study of the resulting materials is a field that has seen dramatic growth in recent years.1 With non-covalent interactions playing a critical role in the assembly of such supramolecular polymers it is not surprising that these materials can exhibit interesting stimuli-responsive behavior,for example highly temperature dependent mechanical properties.2 One subset of such supramolecular materials utilizes low molecular weight,telechelic macromonomers that have supramolecular binding motifs attached to each chain end (Figure 1). Depending on the nature of both the polymeric core and the binding motif,phase segregation can occur resulting in a supramolecular network architecture (e.g. Figure 1b) comprised of "hard" binding motif phases in a "soft" core polymer matrix. As a consequence of such an assembly,dynamic network behavior arises from the formation of labile cross-links by the supramolecular hard blocks.3 If properly designed,such a supramolecular material can possess a thermal transition where the nature of the phase segregated network changes and the modulus of the system is drastically reduced. In this case,the telechelic systems are comparable to A-B-A block copolymers,albeit generally of lower molecular weight and with specific non-covalent interactions (e.g. hydrogen bonding) in the hard phase. We have been investigating the potential of aromatic amides,e.g. protected nucleobases,to provide a convenient supramolecular hard block with a strong tendency to phase segregate from common low-Tg polymers.