Cyclodextrins complexes with polymers

Addition of an aqueous solution of PEG to a saturated aqueous solution of a-CD at room temperature did not lead to complex formation unless the average molecular weight of PEG exceeded 200 [46]. Moreover, carbohydrate polymers such as dextran and pullulan failed to precipitate complexes with PEG, and the same was true for amylose, glucose, methyl glucose, maltose, maltotriose, cyclodextrin derivatives, such as glucosyl-a-CD and maltosyl-a-CD, and water-soluble polymers of a-CD crosslinked by epichlorohydrin. These facts suggested to Harada et al. the direction for further research. 

Table 1. Comparison of hydrophilic polymers with various chain cross-sectional areas in formation of crystalline complexes with cyclodextrins...

Low affinity to polar solvents and fullerenes aggregation in water limit their use in biologic systems. To increase water solubility of fullerenes, few ways are used solubilization with the use of some water-soluble polymers like PDT or polyvin-ilpyrrolidone, generation of complexes with cyclodextrines or calixarenes, and... 

Faucci, M. T. and P. Mura (2001). Effect of water-soluble polymers on naproxen complexation with natural and chemically modi e0-cyclodextrins.Drug Dev. Ind. Pharm., 27 909-917. 

Adsorption chromatography on cellulose was examined for azo dyes that form complexes with CDs using aqueous solutions of a-CD as eluents. The cyclodextrin substantially increases the RF values [61], Commercial a-, [>-. and y-CD polymers were used for the same purpose, however changes of RF were observed only for some azo dyes [62], 2-Hydroxypropyl-P-cyclodextrin used in 10-20% concentration causes complete elution of many compounds [63],... 

Storsberg, J. Glockner, P. Eigner, M. Schnoller, U. Ritter, H. Voit, B. and Nuyken, O. (2001) Cyclodextrins in polymer synthesis photocrosslinkable films via free radical copolymerization of methylated / -cyclodextrin-complexed styrene with sodium 4-(acrylamido)-phenyldiazosulfonate in aqueous medium, Designed Monomers and Polymers 4, 9-17. 

Summary The analysis of supramolecular structures containing polymers, and the discussion about the effect of polymeric materials with different chemical structures that form inclusion complexes is extensively studied. The effect of the inclusion complexes at the air-water interface is discussed in terms on the nature of the interaction. The entropic or enthalpic nature of the interaction is analyzed. The description of these inclusion complexes with different cyclodextrines with several polymers is an interesting way to understand some non-covalent interaction in these systems. The discussion about the generation and effect of supramolecular structures on molecular assembly and auto-organization processes is also presented in a single form. The use of block copolymers and dendronized polymers at interfaces is a new aspect to be taken into account from both basic and technological interest. The effect of the chemical structure on the self-assembled systems is discussed. 

Potential use of complexes of y - CD with organic compounds, including polymers, was also reviewed by Szejtli [6, 12, 13], y - CD are able to incorporate metal ions as ligands to prepare magnetic nano - particles [7,14], Harada and Ka-machi [8,15] first found that poly (ethylene oxide) (PEO) thread a- CD rings to form polymer - cyclodextrin complex. Since their finding of inclusion complex formation of polymer chains with a- CD, a large number of studies on inclusion complexes of... 

In the supramolecular systems as the complexes of polymers and copolymers with cyclic molecules as cyclodextrins, the surface properties and the molecular motion must change when the polymer is free that when the polymer is included inside of a cyclic molecule. The polymer in the complexed form cannot have the same situation when it is in uncomplexed state. 

Derivatives with decreased solubility in water have also been made. By crosslinking cydodextrins with epichlorohydrin, an insoluble polymer is formed. The polymeric cyclodextrin is able to form complexes with soluble compounds and remove them from solution. 

Many fruit and vegetable juices darken in color with time due to enzymic browning. The phenolic compounds involved in the reaction complex with cyclodextrin. Thus, the browning reaction can be prevented, either by passing the juice through a crosslinked cyclodextrin polymer to remove the phenol, or by adding cyclodextrin to the juice, since polyphenoloxidase, the enzyme responsible for oxidizing the phenolic compounds, is unable to act on the phenolic compounds while they are complexed with the cyclodextrin.98,99... 

The utility of the highly soluble 6-cyclodextrin derivatives (soluble polymer and dimethyl-6-cyclodextrin) in RPTLC is illustrated in the separation of barbiturates. The lipophilicity of a barbiturate or any guest decreases when included in a cyclodextrin-cavity. Therefore its mobility is modified in reversed phase thin layer chromatography. With this simple and rapid method, the stability of a complex can be estimated empirically (Table II). The "b" value of the following equation is characteristic for the complex stability (in water ethanol =4 1 solution, R determined at 5 different cyclodextrin concentrations for 21 barbiturates) ... 

According to the "b" values, the a-cyclodextrin form only weak complexes with barbiturates. The stability of 8-cyclodextrin and y-cyclodextrin complexes is similar and higher. Even higher is the stability with the soluble 8-cyclodextrin-polymer, the highest being with DIMEB (see the X values in Table II). 

The ability of some components of nucleic acids, especially those with an adenine base, to form complex with 8-cyclodextrin, can also be readily used for chromatographic separations of various nucleotides and nucleosides (59). A substantial problem associated with application of cyclodextrin polymer gels, is that the accessibility of the cyclodextrin cavities on the surface and within the interior of the polymer particle is rather different. The rate of entrapment and release of solutes from the streaming liquid is obviously a diffusion controlled process. Consequently, a longer time is needed to reach an equilibrium within the particle than on its surface. The accessibility of the cyclodextrin rings will be more uniform, if the cyclodextrin is immobilized on the surface of non-complexing polymer particles (polyacrylamide, agarose (60,61) cellulose (62), and silica (63)). Therefore, a better separation (however lower capacity) is expected. 

Rearrangements.- E-Photoisomerization occurs readily in imines and in azo compounds. The syn-isomer (1), for example, is the major product of irradiation of nitrofurazone (2) in solution and is formed together with the corresponding azine on exposure to laboratory illumination. The photoisomerization of azobenzene derivatives in solution, in membranes, in host-guest complexes of cyclodextrins, and in polymers continues to attract attention. The reversibility of E-photoisomerization of azobenzene in cyclo-hexane solution has been established, and the E/ -ratios generated by irradiation of various azobenzene derivatives adsorbed on... 

Another aqueous heterogeneous polymerization was recently reported for the precipitation polymerization of MMA and styrene complexed with methylated /3-cyclodextrin.256 The polymerization was carried out in water with 1-21 (X = Br)/CuBr/L-4 to give polymers with controlled molecular weights and relatively narrow MWDs (MJMn = 1.3—1.8). Initially, the reaction mixture was homogeneous with the hydrophilic cyclodextrin-complexed MMA, but sooner or later it became heterogeneous due to the formation of water-insoluble polymers. 

In addition, Harada et al. have recently found that /1-cyclodextrin and y-cyclodextrin formed inclusion complexes with poly(dimethylsiloxane) (PDMS), a typical inorganic polymer in aqueous solution [111, 112]. The au-... 

Poly(benzimidazole) can be used as the reactive polymer for the preparation of side chain-type polyrotaxane via the alkylation on nitrogen. Osakada et al. showed that deprotonation of poly(benzimidazole) followed by N-alkylation with alkyl bromide-terminated pseudorotaxane consisting of 2,3,6-trimethyl-/1-cyclodextrin gave a novel side chain-type polyrotaxane (Scheme 38) [206]. Poly(benzimidazole) having a long -hydroxyalkyl group as the side chain can form an inclusion complex with 2,3,6-trimethyl-/l-cy-... 

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