Dynamers: Polyacylhydrazone reversible covalent polymers, component exchange, and constitutional diversity

Abstract

Component exchange in reversible polymers allows the generation of dynamic constitutional diversity. The polycondensation of dihydrazides with dialdehydes generates polyacylhydrazones, to which the acylhydrazone functionality formed confers both hydrogen-bonding and reversibility features through the amide and imine groups, respectively. Polyacylhydrazones are thus dynamic polyamides. They are able to reversibly exchange either one or both of their repeating monomer units in the presence of different monomers, thus presenting constitutional dynamic diversity. The polymers subjected to monomer exchange͞interchange may be brought to exhibit physical properties vastly different from those of the original polymer. The principle may be extended to other important classes of polymers, giving access, for instance, to dynamic polyureas or polycarbamates. These reversible polymers are therefore able to incorporate, decorporate, or reshuffle their constituting monomers, namely in response to environmental physical or chemical factors, an adaptability feature central to constitutional dynamic chemistry.constitutional dynamic chemistry ͉ reversible polymers ͉ dynamic materials B lending supramolecular chemistry with materials science defines a field of supramolecular materials that rests on the explicit implementation of intermolecular interactions in the design and synthesis of novel materials presenting novel properties.Because supramolecular chemistry is by nature a dynamic chemistry in view of the lability of the noncovalent interactions connecting the molecular components of a supramolecular entity, supramolecular materials are by nature dynamic materials (1-3).Importing such dynamic features, characteristic of supramolecular chemistry, into molecular chemistry implies looking at molecules as labile entities, in contrast to the usual longing for stability, thus opening novel perspectives to covalent chemistry. It requires searching for reversible reactions that allow the making and breaking of covalent bonds, preferentially under mild conditions. These developments are embodied in the recent emergence of dynamic combinatorial chemistry as a powerful means for generating dynamic, effector-responsive molecular diversity (2, 4).Thus, on both the supramolecular and molecular levels, dynamic materials may be defined as materials whose constituents are linked through reversible connections (noncovalent or covalent) and are able to undergo continuous reorganization through assembly͞disassembly processes, incorporation, extrusion, or reshuffling of components in a given set of conditions, usually under thermodynamic control (1, 2).The resulting constitutional plasticity defines a constitutional dynamic chemistry (3) encompassing both covalent molecular (2, 5) and noncovalent supramolecular entities.Focusing on a specific class of materials, polymers, the pathway leads from supramolecular polymers (6-8) to dynamic covalent polymers (see ref. 5, pp. 902-915). One may designate under the term, Dynamers (7), both the polymers that...

Tuning Gas‐Diffusion through Dynameric Membranes: Toward Rubbery Organic Frameworks (ROFs)

“…Within this context, we previously showed that dynamic covalent polymers, [15] or dynamers, [20][21][22][23] generated from reversibly interacting monomers, offer the possibility to address these issues. [24,25] In dynamers, the components are reversibly connected, and they self-assemble in such a fashion that their overall morphology overrides defects during the forAbstract: Obtaining high permeability whilst keeping a reasonable selectivity is the most important challenge in the development of membrane systems for gas separation.…”

Controlled Release of Volatile Aldehydes and Ketones from Dynamic Mixtures Generated by Reversible Hydrazone Formation

“…Numerous hydrazine derivatives are commercially available or can easily be prepared in a few reaction steps (see, e.g., [16]). Particularly interesting in the context of the present studies are acylhydrazines (¼ hydrazides; R'COÀNHÀNH 2 ), as these compounds incorporate a peptide bond together with the imine-forming hydrazine functionality [17]. For our studies, we used alkyl-or arylhydrazines 1a and 2a, sulfonylhydrazine (¼ sulfonic acid hydrazide) 3a, as well as a series of different hydrazides such as semicarbazide (¼ hydrazinecarboxamide) 4a, hydrazinecarboxylate 5a, furoyl-and arylhydrazides (¼ furan-and arenecarboxylic acid hydrazides) 6a -8a, alkylhydrazides (¼ alkanoic acid hydrazides) 9a and 10a, and the Girard T (11a) or P (12a) reagents [18] (Fig.…”

Dynamic Combinatorial Diversity in Drug Discovery

“…Indeed, recent work has uncovered the presence of a binding pocket in the middle of the gorge of the enzyme, a fact in line with the strong activity of the bis-pyridinium inhibitor containing a disubstituted para-phenylene spacer [74]. The field of DCC has been the subject of great interest and activity since the formulation of the concept, as shown by the development of new approaches, e. g. dynamic combinatorial X-ray crystallography [60] or pseudo-dynamic chemistry [49], application of new reversible reactions for DCL generation [44,45] and application to materials science, as for instance in the case of dynamic polymers-dynamers [75][76][77] and the formation of G-quartet-based hydrogels [78].…”