A novel associative polymer network based on cyclodextrin inclusion with tunable rheological properties

A novel associative polymer network with tunable rheological properties is developed based on cyclodextrin-hydrophobe inclusion. The network is formed from mixtures of two polyacrylic acid (PAA) backbone polymers, one with pendant cyclodextrin groups and one with pendant hydrophobic alkyl groups. The lifetime of the cyclodextrin-hydrophobe inclusion can be well controlled by the length of alkyl chains inserted into the cyclodextrins; also, the binary nature of cyclodextrin-hydrophobe inclusion prevents hydrophobes from forming nonstoichiometric multiple associations. This system can serve as a model associative polymer network to test associative polymers theories. Dynamic rheological properties of this mixture solution can be tuned by adding free cyclodextrins or sodium dodecylsulfate (SDS) to displace polymer-to-polymer associations. Dynamic moduli change three orders of magnitude from a gel state to a sol state. The phase behavior of this mixture solution is experimentally studied by light scattering measurements and rheology. The thermodynamics of the cyclodextrin-hydrophobe interaction is independently studied using isothermal titration calorimetry and surface plasmon resonance study.