362
deformation, 850 cm
−1
; and pyranose ring vibrations, 755 cm
−1
. This assignment of
bands was in accordance with that of Professor Wiedenhof.
In 1970, Professor Hoffman proposed materials with high cyclodextrin contents
in bead form for column chromatography. The materials were suitable chromatographic supports for the separation of nucleic acids, nucleotides, nucleosides, and
oligonucleotides. Professor Hoffman also demonstrated that ECP materials were
useful for separating various positional and optical isomers. The results were interpreted not only in terms of inclusion complexation but also by the presence of
anion-exchange interactions, depending on the polymer structure (Hoffman 1970,
1972, 1973).
In the early 1980s, the Hungarian group of Professor Szejtli became very active
in the field of ECP polymers for extraction, concentration, and purification of substances. Many significant results on chromatographic, environmental, and pharmaceutical applications have also been obtained (Szejtli 1980, 1982, 1984, 1988).
Professor Szejtli has clearly demonstrated that cyclodextrin cavities retain their
complexing properties despite the cross-linking reaction. In polymerized form,
cyclodextrin molecules are enclosed in a network with loss of mobility, which, to
some extent, “exacerbated steric hindrance at the entrance to cavities” (Szejtli
1988). However, this steric effect was “less important when the guest molecule was
too large to be fully inserted into a single cavity because a second cyclodextrin molecule in the polymer network can then encapsulate its other extremity.” This was the
first time that this concept had appeared in the literature (Crini 2014). Professor
Szejtli demonstrated that porous polymers had a high adsorption capacity due to
their adsorption strength and large high surface area. The introduction of micro- and
mesopores offered both abundant adsorption sites and open diffusion pathways for
pollutants and thus contributed to improving the adsorption rate. Professor Szejtli
was also the first to demonstrate that the presence of unreacted free epichlorohydrin
(this cross-linking agent is toxic and far from being “green”) in the materials was
unlikely because epichlorohydrin was a highly reactive substance and underwent
hydrolysis under alkaline reaction conditions. This was important for potential
applications in the pharmaceutical field (Szemán et al. 1987; Fenyvesi 1988).
At the end of the 1980s, the main applications of the cyclodextrin polymers consisted of their use in low-pressure liquid chromatography to separate proteins,
nucleic acids, mandelic acid derivatives, aromatic amino acids, vitamins, and perfumes (Szejtli 1980, 1982, 1988; Zsadon et al. 1981; Smolkova-Keulemansova
1982), in gas chromatography (Cserháti et al. 1983), in food industry to remove
bitter substances from filtered orange and grapefruit juices using batch and column
debittering procedures (Shaw and Wilson 1983, 1985; Wagner et al. 1988; Shaw
1990), and also in pharmacy (Szejtli et al. 1978; Szemán et al. 1987; Fenyvesi
1988). From the late 1990s onward, many patents and publications on environmental applications began to appear (Friedman and West 1988; Vanzo 1991; Cserháti
and Forgács 1994). Over the past two decades, cyclodextrin polymers have gained
considerable attention for their performance in environmental remediation-based
applications. In an industry dominated by activated carbons and organic resins, in
G. Crini
deformation, 850 cm
−1
; and pyranose ring vibrations, 755 cm
−1
. This assignment of
bands was in accordance with that of Professor Wiedenhof.
In 1970, Professor Hoffman proposed materials with high cyclodextrin contents
in bead form for column chromatography. The materials were suitable chromatographic supports for the separation of nucleic acids, nucleotides, nucleosides, and
oligonucleotides. Professor Hoffman also demonstrated that ECP materials were
useful for separating various positional and optical isomers. The results were interpreted not only in terms of inclusion complexation but also by the presence of
anion-exchange interactions, depending on the polymer structure (Hoffman 1970,
1972, 1973).
In the early 1980s, the Hungarian group of Professor Szejtli became very active
in the field of ECP polymers for extraction, concentration, and purification of substances. Many significant results on chromatographic, environmental, and pharmaceutical applications have also been obtained (Szejtli 1980, 1982, 1984, 1988).
Professor Szejtli has clearly demonstrated that cyclodextrin cavities retain their
complexing properties despite the cross-linking reaction. In polymerized form,
cyclodextrin molecules are enclosed in a network with loss of mobility, which, to
some extent, “exacerbated steric hindrance at the entrance to cavities” (Szejtli
1988). However, this steric effect was “less important when the guest molecule was
too large to be fully inserted into a single cavity because a second cyclodextrin molecule in the polymer network can then encapsulate its other extremity.” This was the
first time that this concept had appeared in the literature (Crini 2014). Professor
Szejtli demonstrated that porous polymers had a high adsorption capacity due to
their adsorption strength and large high surface area. The introduction of micro- and
mesopores offered both abundant adsorption sites and open diffusion pathways for
pollutants and thus contributed to improving the adsorption rate. Professor Szejtli
was also the first to demonstrate that the presence of unreacted free epichlorohydrin
(this cross-linking agent is toxic and far from being “green”) in the materials was
unlikely because epichlorohydrin was a highly reactive substance and underwent
hydrolysis under alkaline reaction conditions. This was important for potential
applications in the pharmaceutical field (Szemán et al. 1987; Fenyvesi 1988).
At the end of the 1980s, the main applications of the cyclodextrin polymers consisted of their use in low-pressure liquid chromatography to separate proteins,
nucleic acids, mandelic acid derivatives, aromatic amino acids, vitamins, and perfumes (Szejtli 1980, 1982, 1988; Zsadon et al. 1981; Smolkova-Keulemansova
1982), in gas chromatography (Cserháti et al. 1983), in food industry to remove
bitter substances from filtered orange and grapefruit juices using batch and column
debittering procedures (Shaw and Wilson 1983, 1985; Wagner et al. 1988; Shaw
1990), and also in pharmacy (Szejtli et al. 1978; Szemán et al. 1987; Fenyvesi
1988). From the late 1990s onward, many patents and publications on environmental applications began to appear (Friedman and West 1988; Vanzo 1991; Cserháti
and Forgács 1994). Over the past two decades, cyclodextrin polymers have gained
considerable attention for their performance in environmental remediation-based
applications. In an industry dominated by activated carbons and organic resins, in
G. Crini