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Well-defined fluorocarbon end-capped poly(ethylene oxide) (PEO), known as F-HEUR, were synthesized by varying both fluorocarbon end groups and PEO chain length. Their solution properties were studied and compared with those of hydrogenated carbon end-capped PEO. Variation of the end-capped functional group from -C 6 F 13 to -C 8 F 17 gave rise to a significant shift in the solution rheological properties. The interaction between different cyclodextrins and these fluorocarbon derivatives of PEO was systematically examined by rheological, dynamic light scattering (DLS), isothermal titration calorimetric (ITC), and 19 F NMR techniques. The viscosity of F-HEUR solution was drastically reduced in the presence of methylated β-cyclodextrin (m-βCD) due to the disruption of intermolecular hydrophobic associations, but not observed for Rand γ-cyclodextrins. The destruction of F-HEUR network structure in the presence of m-βCD was reflected by the large reduction in the plateau modulus (G N 0 ). The activation energies (E a ) determined from zero-shear viscosity decreased with m-βCD concentration until a molar ratio of 2; thereafter it remained constant. At high m-βCD concentration, subtle difference was observed for the complexes produced by -C 6 F 13 and -C 8 F 17 hydrophobic moieties. The inclusion complex formation between m-βCD and different fluorocarbon groups derived from ITC thermograms revealed a stoichiometry of 1:1 for C 6 F 13 but 1:1 and 2:1 inclusion complexes for C 8 F 17 at different m-βCD concentrations. DLS results showed a different mechanism for C 6 F 13 and C 8 F 17 fluorocarbon hydrophobes, which were in agreement with the results deduced from activation energies and 19 F NMR spectra. A mathematic model was adopted to describe the relationship between G N 0 and m-βCD concentration.

The viscosity of hydrophobic ethoxylated urethane (HEUR) solution decreased in the presence of alpha-CD or m-beta-CD; however their interactions were quite different. When the alpha-CD/hydrophobe molar ratio exceeded 5.0, the viscosity was close to that of a PEO solution of similar molecular weight. Oscillatory shear indicated that the mechanically active chains in HEUR solution decreased with the addition of alpha-CD. This agreed with the hypothesis that alpha-CD formed an inclusion complex with the hydrophobic moiety of the HEUR polymer, thereby destroying the transient hydrophobic associative network. The viscosity/temperature relationship of the alpha-CD/HEUR system (for HEUR with 70% of the PEO chains capped at both ends) did not obey the Arrhenius relationship for alpha-CD/hydrophobe molar ratio in the range 0.8-5.0. The low shear viscosity increased with increasing temperature at molar ratio of 1.0, and this was attributed to the competitive complexation of the alpha-CD/hydrophobe and the alpha-CD/PEO chain. Increasing temperature favored alpha-CD/PEO complexation. Comparison between the behavior of alpha-CD/HEUR and m-beta-CD/HEUR resulting from the different binding characteristics was discussed.

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The solution properties of various types of telechelic hydrophobically modified ethylene oxide urethane polymer (HEUR) in the presence of cyclodextrins were examined. Methylated (3-cyclodextrin (m-pCD) could effectively reduce the steady shear viscosity and the dynamic moduli of HEUR aqueous solutions. It was found that m-PCD interacts with HEUR in three progressive steps. At very low m-(3CD concentrations, m-pCD encapsulates the hydrophobes of looping HEUR chains, which destabilizes the transient network, while maintaining the number of mechanically active chains. However, the m-pCD/HEUR complex solutions become more sensitive to shear stress. At moderate m-pCD concentrations, m-pCD begins to deactivate the bridging chains resulting in a reduction in the number of mechanically active chains and this further weakens the transient network. Finally, when m-pCD is in excess, the network Methylated P-Cyclodextrin could effectively reduce the steady shear viscosity and dynamic moduli of HEUR aqueous solutions. a-Cyclodextrin was found to reduce the steady shear viscosity and dynamic moduli of HEUR aqueous solutions. However, rehological studies revealed some subtle differences between a-CD/HEUR and m-pCD/HEUR system. For the m-pCD/HEUR system, the temperature dependence of low shear viscosity can be described by Arrhenius equation. On the other hand in a-CD/HEUR system, the low shear viscosity ~ temperature relationship does not follow the Arrhenius relationship, where the viscosity increases with increasing temperature within a defined temperature range, Exhibiting a unique viscosity recovery at elevated temperature. The transient hydrophobic network, which is suppressed by the addition of a-CD is partially restored with increasing temperature, which is evident by dynamic mechanical measurements.