Chapter 4
Dynamic Covalent Gels
Abstract Various dynamic covalent bonds have been studied in the area of
supramolecular gels, such as imine/acylhydrazone formation, boronic ester formation, disulphide formation and anthracene dimerization. Two catalogues of
dynamic covalent gels are discussed in this chapter, namely gelation by discrete
molecules and gelation by dynamic covalent polymers. Discrete gelators include
imine/acylhydrazone gels, borate gels, anthracene-based gels and gels based on
dynamic covalent cycles and cages. In the section of dynamic covalent polymer
gels, imine gels and calix[4]arene-derived acylhydrazone gels are discussed in
detail.
Keywords Dynamic covalent chemistry Á Supramolecular gels
Imine Á Acylhydrazone Á Cage compounds
Dynamic covalent chemistry, first introduced by Lehn, studies the formation of
reversible covalent bonds under thermodynamic control [1]. The development of
dynamic covalent chemistry has opened up new opportunities for the design and
fabrication of supramolecular gels [2–4]. Compared with non-covalently bonded
molecular systems, the formation of dynamic covalent bonds between gelators can
potentially enhance the toughness and stability of resulting gels. To date, a number
of dynamic covalent bonds have been studied in the area of supramolecular gels [5].
The functionalization of gelators with bond-forming groups allows control over the
backbone structures of gel networks. The dynamic reactions that have been applied
for gels include formation of imines, hydrazones, acylhydrazones, Diels–Alder
cycloaddition, boronic esters, disulfides and so on (Scheme 4.1). Catalysts are often
needed in order to access the reversibility of these bonds such as acid, base and
redox agents.
Condensations of amino and carbonyl groups to give C=N compounds (imines
or hydrazones) are one of the frequently used dynamic covalent reactions [6, 7].
The imine bond is formed by the reversible condensation between a primary amine
Jianyong Zhang, Haobin Fang and Xiying Feng contributed together to this chapter.
© Springer Nature Singapore Pte Ltd. 2018
J. Zhang et al., Gel Chemistry, Lecture Notes in Chemistry 96,
https://doi.org/10.1007/978-981-10-6881-2_4
119
Dynamic Covalent Gels
Abstract Various dynamic covalent bonds have been studied in the area of
supramolecular gels, such as imine/acylhydrazone formation, boronic ester formation, disulphide formation and anthracene dimerization. Two catalogues of
dynamic covalent gels are discussed in this chapter, namely gelation by discrete
molecules and gelation by dynamic covalent polymers. Discrete gelators include
imine/acylhydrazone gels, borate gels, anthracene-based gels and gels based on
dynamic covalent cycles and cages. In the section of dynamic covalent polymer
gels, imine gels and calix[4]arene-derived acylhydrazone gels are discussed in
detail.
Keywords Dynamic covalent chemistry Á Supramolecular gels
Imine Á Acylhydrazone Á Cage compounds
Dynamic covalent chemistry, first introduced by Lehn, studies the formation of
reversible covalent bonds under thermodynamic control [1]. The development of
dynamic covalent chemistry has opened up new opportunities for the design and
fabrication of supramolecular gels [2–4]. Compared with non-covalently bonded
molecular systems, the formation of dynamic covalent bonds between gelators can
potentially enhance the toughness and stability of resulting gels. To date, a number
of dynamic covalent bonds have been studied in the area of supramolecular gels [5].
The functionalization of gelators with bond-forming groups allows control over the
backbone structures of gel networks. The dynamic reactions that have been applied
for gels include formation of imines, hydrazones, acylhydrazones, Diels–Alder
cycloaddition, boronic esters, disulfides and so on (Scheme 4.1). Catalysts are often
needed in order to access the reversibility of these bonds such as acid, base and
redox agents.
Condensations of amino and carbonyl groups to give C=N compounds (imines
or hydrazones) are one of the frequently used dynamic covalent reactions [6, 7].
The imine bond is formed by the reversible condensation between a primary amine
Jianyong Zhang, Haobin Fang and Xiying Feng contributed together to this chapter.
© Springer Nature Singapore Pte Ltd. 2018
J. Zhang et al., Gel Chemistry, Lecture Notes in Chemistry 96,
https://doi.org/10.1007/978-981-10-6881-2_4
119