357
porous cyclodextrins polymers can require long reaction times, and the type of
cross-linking agent strongly influences the pore diameter. Nevertheless, synthesis in
aqueous media is generally preferred because of their simplicity and their more
ecological nature (Crini and Morcellet 2002; Crini 2005a; Morin-Crini et al. 2013,
2018a). Xu et al. (2019) recently proposed for the first time the synthesis of an ultraporous polymer in aqueous phase.
Nowadays, several materials with different characteristics in terms of cross-link
density, surface area, pore structure, and physical and chemical properties can be
obtained. They can be precisely tailored to have desired architectures and functionalities. This explains the fact that, although the cross-linking of cyclodextrin molecules with epichlorohydrin has been known for more than half a century, it continues
to be of interest to the scientific community (Euvrard et al. 2017; Crini et al. 2018a,
b; Morin-Crini et al. 2018a). Ongoing work is proposing innovative macromolecular architectures in the form of foams, nanoparticles, nanosponges, fibers (nanofibers/nanowebs), felts, membranes/nanomembranes, “intelligent” hydrogels,
composites, or film-based products. These materials are developed for various
applications not only in the environmental field, for example, the elimination of the
so-called emergent pollutants (pesticides, drugs, endocrine disruptors, etc.) present
in polluted water or soil and air filtration, but also in the pharmaceutical or medical
fields (drug delivery, biomedicine) or in innovative fields (medical textiles, composites for packaging, encapsulation of essential oils and volatiles, nanocatalysis, nanoelectronics) (Crini et al. 2019a).
8.2.4 Chemical Modification of Cyclodextrin-Epichlorohydrin
Polymers
The chemical modification of a cyclodextrin-based material is an interesting step to
introduce specific properties in order to broaden the scope of its potential applications. This was first suggested by Professor French in the 1950s and then studied by
Professor Casu in the 1960s (Crini 2014). In general, the objectives are to improve
pollutant adsorption properties, to increase selectivity for target pollutants, and to
prepare amphoteric polymers. For example, the functionalization of ECP materials
can modify characteristics of this class of gel such as selectivity when forming
inclusion complexes. By replacing one or more OH groups at a “desired” position
and with an appositely designed substitution group, multisite recognition systems
can be obtained (Crini and Morcellet 2002). The preparation of homogeneous,
selectively derivatized ECP is, however, not an easy task, as reported by Professor
Szejtli in the 1980s.
The literature suggests two main methods for modifying ECP materials. The first
method was introduced by Professor French in the 1950s and adopted by Professor
Wiedenhof in the 1960s and Professor Szejtli in the 1980s (Crini 2014; Morin-Crini
et al. 2018a). It consists in grafting specific moieties onto the materials after
8 Water-Insoluble Cyclodextrin-Epichlorohydrin Polymers
porous cyclodextrins polymers can require long reaction times, and the type of
cross-linking agent strongly influences the pore diameter. Nevertheless, synthesis in
aqueous media is generally preferred because of their simplicity and their more
ecological nature (Crini and Morcellet 2002; Crini 2005a; Morin-Crini et al. 2013,
2018a). Xu et al. (2019) recently proposed for the first time the synthesis of an ultraporous polymer in aqueous phase.
Nowadays, several materials with different characteristics in terms of cross-link
density, surface area, pore structure, and physical and chemical properties can be
obtained. They can be precisely tailored to have desired architectures and functionalities. This explains the fact that, although the cross-linking of cyclodextrin molecules with epichlorohydrin has been known for more than half a century, it continues
to be of interest to the scientific community (Euvrard et al. 2017; Crini et al. 2018a,
b; Morin-Crini et al. 2018a). Ongoing work is proposing innovative macromolecular architectures in the form of foams, nanoparticles, nanosponges, fibers (nanofibers/nanowebs), felts, membranes/nanomembranes, “intelligent” hydrogels,
composites, or film-based products. These materials are developed for various
applications not only in the environmental field, for example, the elimination of the
so-called emergent pollutants (pesticides, drugs, endocrine disruptors, etc.) present
in polluted water or soil and air filtration, but also in the pharmaceutical or medical
fields (drug delivery, biomedicine) or in innovative fields (medical textiles, composites for packaging, encapsulation of essential oils and volatiles, nanocatalysis, nanoelectronics) (Crini et al. 2019a).
8.2.4 Chemical Modification of Cyclodextrin-Epichlorohydrin
Polymers
The chemical modification of a cyclodextrin-based material is an interesting step to
introduce specific properties in order to broaden the scope of its potential applications. This was first suggested by Professor French in the 1950s and then studied by
Professor Casu in the 1960s (Crini 2014). In general, the objectives are to improve
pollutant adsorption properties, to increase selectivity for target pollutants, and to
prepare amphoteric polymers. For example, the functionalization of ECP materials
can modify characteristics of this class of gel such as selectivity when forming
inclusion complexes. By replacing one or more OH groups at a “desired” position
and with an appositely designed substitution group, multisite recognition systems
can be obtained (Crini and Morcellet 2002). The preparation of homogeneous,
selectively derivatized ECP is, however, not an easy task, as reported by Professor
Szejtli in the 1980s.
The literature suggests two main methods for modifying ECP materials. The first
method was introduced by Professor French in the 1950s and adopted by Professor
Wiedenhof in the 1960s and Professor Szejtli in the 1980s (Crini 2014; Morin-Crini
et al. 2018a). It consists in grafting specific moieties onto the materials after
8 Water-Insoluble Cyclodextrin-Epichlorohydrin Polymers