Modulation of Hydrophobic Interactions in Associative Polymers Using Inclusion Compounds and Surfactants

Abstract

We report the modulation of the solution rheology of a comblike, hydrobhobically modified alkali-soluble emulsion (HASE) associative polymer through addition of R-and β-cyclodextrins (CDs). The ring-shaped CDs with hydrophobic inner cores interact with the pendant macromonomer segments of the associative polymer containing hydrophobic end groups, leading to reduction in polymer solution viscosity and dynamic moduli by several orders of magnitude. We find no interactions between the CDs and the polymer backbone as substantiated by the fact that an analogous parent polymer without hydrophobes reveals no changes in the solution rheology in the presence of CDs. In contrast, the CDs encapsulate the hydrophobic groups on the associative polymer. This is confirmed by the complexation between the CD and a surfactant modified to resemble the hydrophobic macromonomer of the associative polymer as observed using 1 H NMR, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). The stoichiometric ratio of complexation between the CD and the hydrophobic macromonomer is determined independently from both NMR and yield data to be 5 mol of CD/mol of hydrophobe. Interestingly, the reduction in polymer viscoelasticity in the presence of CD is reversibly recovered upon subsequent addition of different nonionic surfactants that have a higher propensity to complex with the CD than the hydrophobic segments of the HASE polymer.

Rheological Properties of a Telechelic Associative Polymer in the Presence of α- and Methylated β-Cyclodextrins

“…12 This concept is based on the idea of using cyclodextrin to encapsulate hydrophobic segments so that the molecular properties of single chain and the solution viscosity of associative polymers can be controlled. 13, 14 Karlson 15,16 proposed a simple Langmuir adsorption model for describing the complexation mechanism between cyclodextrin and hydrophobically modified PEO. They concluded that cyclodextrin molecules could complex with hydrophobic end groups of associative polymers resulting in the disruption of the three-dimensional associating network.…”

Preparation and investigation of acetyl salicylic acid-caffeine complex for rectal administration

“…These data indicated the formation of complex in a 1:1 stoichiometric ratio. Abdala et al [32] calculated the stoichiometric ratio of a complex formed between cyclodextrin and a macromonomer using the integral area under the 1 H proton of the 1 H NMR.…”

Dynamic light scattering of semidilute hydrophobically modified alkali‐soluble emulsion solutions with different lengths of poly(ethylene oxide) spacer chain

“…The nature of association mechanism and the conformation of polymer chains in solution are controlled by the equilibrium between the hydrophobic attraction and the electrostatic repulsion. It has been observed that these aggregates could be destroyed by the addition of excess amounts of surfactants or β‐cyclodextrin 10–13, 24…”