Amylose brushes

Amylose brushes (a layer consisting of polymer chains dangling in a solvent with one end attached to a surface is frequently referred to as a polymer brush) on spherical and planar surfaces can have several advantageous uses, such as detoxification of surfaces etc. The modification of surfaces with thin polymer films is widely used to tailor surface properties such as wettability, biocompatibility, corrosion resistance, and friction [142-144]. The advantage of polymer brushes over other surface modification methods like self-assembled monolayers is their mechanical and chemical robustness, coupled with a high degree of synthetic flexibility towards the introduction of a variety of functional groups. 

The first surface-initiated enzymatic polymerization reported was the synthesis of amylose brushes on planar and spherical surfaces [145]. For this, silica or silicone surfaces were modified with self-assembled monolayers of (3 amino-propyl)trimethoxysilane or chlorodimethylsilane, respectively. To these functionalities, oligosaccharides were added via (a) reductive amidation of the oligosaccharides to surface-bound amines, (b) conversion of the oiigosaccharide to the according aldonic acid lactone and reaction with surface bound amines, and (c) incorporation... 

Cellulose derivatives Amylose derivatives Brush-type... 

The most successful and broadly applied chiral stationary phases comprise the cellu-lose-and amylose-based phases developed by Okamoto (Chiracel and Chiralpak) (39), brush-type phases developed by Pirkle (40),... 

Indicates chiral carbons. The chirality of the phases is not specified here some of the brush-type phases are available in both enantiomeric forms. The chirality is given for cellulose, amylose, cyclodextrin, vancomycin, and the proteins. 

Haddleton and Ohno reported on maltodextrin modified polymers via copper(I)-mediated living radical polymerization [125]. Comblike structures based on polystyrene with amylose entities were synthesized by Kobayashi et al. [126] and bottle-brush-like structures by Kakuchi and coworkers [127]. 

Chiral stationary phases can exist in different forms [10] (see Fig. 8). Some selectors can be used as particulate phase materials, such as polymeric cellulose triacetate. Polymeric cellulose and amylose derivatives are often coated onto silica carrier particles so that only 20% of the CSP consists of the chiral selector. This combination of stationary phase and chiral polymer combines good chromatographic properties (due to the homogeneous particle size distribution) with a high density of chiral adsorption sites in the polysaccharide derivatives. Another approach is selected for the so-called brush-type CSPs. In these, the chiral selector is covalently bound to the surface of the silica particles. These phases show high chemical inertness and allow the use of a multitude of different mobile phases. 

Very often, analysis times are shortened by using SFC. CSPs compatible with SFC are cellulose and amylose derivatives, brush-type CSPs, as well as macrocyclic phases. The selectivity of the CSPs is in many cases similar to that found on these phases in the normal-phase mode. 

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