Polyacylhydrazones

C=N bonds in acylhydrazone groups, which are formed by the condensation of hydrazides with carbonyl groups, exhibit reversibility under mild conditions. Like polyimines, polymers with acylhydrazone functionalities exhibit dynamic aspects through the reversibihty of the azomethine bond. Skene and Lehn have reported the synthesis of polyacylhydrazones and their dynamic features (Scheme 8.3) [23]. High molecular weight polyacylhydrazone 13 was prepared by the condensation of the corresponding dihydrazide and dialdehyde in the presence of an acid catalyst. When 13 was treated with aryl dialdehyde 14 or aryl dihydrazide 15 in... 

Scheme 8.3 Exchanges of the components in polyacylhydrazone 13 with (a) dialdehyde 14 and (b) bifnnctional acylhydrazide 15 throngh the C=N exchange reaction [23],...

Lehn s group has also reported a series of research related to the improvement of polymer properties using the dynamic feature of polyacylhydrazone (Figs. 8.4—8.7) [24,25], Polymers containing acylhydrazone bonds in linear main chains, 25 and 26, were prepared from the corresponding bifimctional acylhydrazides 18 and 19 and dialdehydes 21 and 22. 

Figure 8.4 Synthetic schemes of polyacylhydrazones 25-28 and stractures of their monomers bifunctional acylhydrazides 18-20 and dialdehydes 21-24 [24,25],...

Skene, W. G. Lehn, J.-M. Dynamers Polyacylhydrazone reversible covalent polymers, component exchange, and constitutional diversity. Proc. Natl. Acad. Sci. U.S.A. 2004,101, 8270-8275. 

Polyacylhydrazones Having Guaiacyl Units with Alkylene Groups... 

Polyacylhydrazones [X] having two guaiacyl units with the alkylene groups in each repeating unit were synthesized using vanillin and dibromoalkanes as starting materials as shown in Scheme 5 (10). 

Figure 5. Heat capacities of polyacylhydrazones, X s, quenched at around T 2A, 4A, 6A m=2, 4, 6 and R=(CH2)4, respectively. (Reprinted with permission from ref. 10. Copyright 1983 Sen-i Gakkaishi.)...

Folmer-Andersen JF, Lehn JM (2009) Constitutional adaptation of dynamic polymers hydrophobically driven sequence selection in dynamic covalent polyacylhydrazones. Angew Chem Int Ed Engl 48 7664—7667... 

Polyacylhydrazone (Scheme ) derivatives having guaiacyl groups in the repeating unit were synthesized using vanillin and dibromoalkane as starting materials. When... 

Hirose, S., Hatakeyama, H., and Hatakeyama, T., 1983, Synthesis and thermal analysis of polyacylhydrazones having guaiacyl units with alkylene groups. Sen-i Gakkaishi 39 496-500. 

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