Complex Formation of β-Cyclodextrin- and Perfluorocarbon-Modified Water-Soluble Polymers

Abstract

The complex formation has been studied by 19F NMR and viscometry of β-cyclodextrin (β-CD) and water-soluble telechelic and one-ended perfluorocarbon derivatives (C6F13 and C8F17) of poly(ethylene glycol)s (PEGs) of molecular weights of 5000 and 10000 and poly(dimethylacrylamide)s containing C8F17 pendent groups. Fluorine-19 NMR of the PEG derivatives shows CF3 resonances at about −80 and −82 ppm corresponding to monomeric and associated structures, respectively. For the case of the one-ended C6F13 PEG (M = 5000) derivatives, a formation constant on the order of 104 was determined. Addition of β-CD to this polymer leads to the formation of 1:1 β-CD−RF complexes that gives CF3 resonances that are very close to that of the monomeric RF groups. Essentially quantitative complex formation with β-CD was observed in the presence of free β-CD concentrations larger than about 10-2−10-3 M. The reduced viscosity of 1.0 wt % aqueous solutions of the telechelic PEG of MW of 10 000 containing C8F17 end groups is greatly reduced as a result of intermolecular hydrophobic association. Addition of stoichiometric β-CD completely suppresses hydrophobic association in this solution, as demonstrated by a virtually complete loss of viscosity due to association. Similar reductions in viscosity were observed for the case of poly(dimethylacrylamide) containing pendent groups. In this case a larger excess of β-CD was required to completely suppress RF association.

Effects of β-cyclodextrin and β-cyclodextrin polymer addition and temperature on the modulation of hydrophobic interactions in aqueous solutions of two hydrophobically modified biopolymers

“…The gradual decrease of the viscosity is attributed to the formation of complexes between the CD molecules and the hydrophobic moieties through a process where the polymer hydrophobic tails are hidden within the CD cavities, and thereby the hydrophobic associations are decoupled. This type of behavior has been reported [1,2,5,[8][9][10][11][12] for hydrophobically modified polymers of various natures in the presence of cyclodextrin monomers. It is interesting to note that in spite of the high molecular weight of poly(b-CDN + ), the aqueous solution of this cosolute has a very low viscosity, which suggests that the branched structure of this compound yields compact molecules.…”

“…In recent years, the interaction between cyclodextrin monomers and nonionic amphiphilic polymers has attracted a great deal of interest [1][2][3][4][5][6][7][8][9][10][11][12][13]. Cyclodextrin monomers are water-soluble cyclic oligosaccharides consisting of six (a-CD), seven (b-CD), eight (c-CD), or more D-glucopyranose units.…”

“…In aqueous solution in the presence of a polymer with attached hydrophobic groups, the CD molecules relatively hydrophobic cavity can accommodate the hydrophobic tails of the polymer leading to deactivation of hydrophobic interactions. Several studies [1,2,[5][6][7][8][9][10][11][12][13][14] have shown that the intensity of the hydrophobic interactions can be tuned by adding different amounts of cyclodextrin compounds. It has been established [15][16][17] that CD molecules form inclusion complexes with the hydrophobic moieties through a process where the hydrophobic tails of the polymer chains are hidden within the CD cavities and thereby decouple hydrophobic associations.…”

Polyrotaxanes

“…The cross-sectional area and the size of the CDs are (52,55,56) correlated. Perfluorinated oligomers (45) and perfluorocarbon-modified PEGs (46) formed inclusion complexes with CDs. Other water-soluble polyethers, such as poly(tetramethylene oxide) (PTHF) (40), poly(ethyl vinyl ether) (PEVE) (43), and poly(n-propyl vinyl ether) (PnPVE) (43) form polypseudorotaxanes with CDs, as described in Table 2.…”

Macromolecular Assemblies Generated by Inclusion Complexes between Amphipathic Polymers and β-Cyclodextrin Polymers in Aqueous Media

“…In addition to these applications, inclusion complexes allow creation of supramolecular structures due to the highly specific non-covalent binding between the cyclodextrin host and the guest molecule. The use of water-soluble polymers in combination with β-cyclodextrin gives rise to two different kinds of structures: a) when β-cyclodextrin interacts directly with the backbone unite of the polymer, necklace structures called polyrotaxanes (or pseudopolyrotaxanes), in which many cyclic molecules are threaded along the linear polymeric chain, are obtained (4) and b) β-cyclodextrin acts as a structure breaker when added to amphiphilic copolymers, binding directly to the hydrophobic side groups and breaking up the hydrophobic microdomains (5). A variety of structures can be obtained by interacting a β-cyclodextrin polymer (a polymer incorporating several β-cyclodextrin units) and an amphiphilic copolymer in aqueous media (6)(7)(8)(9)(10).…”