Modula t ion of Hydrophobic In teract ions in Associa t ive Polymers Using Inclusion Compounds and Surfactan ts

We repor t the modula t ion of the solu t ion rheology of a comblike, hydrobhobica lly modified a lka li-soluble emulsion (HASE) associa t ive polymer through addit ion of Rand !-cyclodext r ins (CDs). The r ing-shaped CDs with hydrophobic inner cores in teract with the pendant macromonomer segments of the associa t ive polymer conta in ing hydrophobic end groups, leading to reduct ion in polymer solu t ion viscosity and dynamic moduli by severa l orders of magnitude. We find no in teract ions between the CDs and the polymer backbone as substan t ia ted by the fact tha t an ana logous paren t polymer without hydrophobes revea ls no changes in the solu t ion rheology in the presence of CDs. In cont rast , the CDs encapsula te the hydrophobic groups on the associa t ive polymer . This is confirmed by the complexa t ion between the CD and a surfactant modified to resemble the hydrophobic macromonomer of the associa t ive polymer as observed using 1H NMR, differen t ia l scanning ca lor imet ry (DSC), and thermal gravimet r ic ana lysis (TGA). The stoich iomet r ic ra t io of complexa t ion between the CD and the hydrophobic macromonomer is determined independent ly from both NMR and yield da ta to be 5 mol of CD/mol of hydrophobe. In terest ingly, the reduct ion in polymer viscoelast icity in the presence of CD is reversibly recovered upon subsequent addit ion of differen t nonionic sur factan ts tha t have a higher propensity to complex with the CD than the hydrophobic segments of the HASE polymer .