Title

Water-Soluble Polymers. 80. Rheological and Photophysical Studies of pH-Responsive Terpolymers Containing Hydrophobic Twin-Tailed Acrylamide Monomers

Document Type

Article

Publication Date

7-31-2001

Department

Polymers and High Performance Materials

Abstract

To examine the effects of microblock hydrophobicity on interpolymer association behavior, a series of terpolymers composed of acrylic acid, methacrylamide, and a DiC(12)AM, DiC(14)AM, or DiC(16)AM twin-tailed hydrophobic monomer have been synthesized using micellar polymerization methods, The terpolymer incorporating the DiC(12)AM hydrophobe possesses the highest initial viscosity and lowest critical yield stress in aqueous solution, while the terpolymer incorporating the DiC(14)AM hydrophobic monomer showed a slightly lower initial viscosity and critical yield stress. The pH response of these terpolymers was examined via rheology and fluorescence energy transfer (NRET) measurements. Dynamic frequency sweeps measured as a function of solution pH reveal viscoelastic behavior consistent with a simple Maxwell model. It is proposed that the number density of network junctions and the residency of hydrophobes in the junctions increase with pH. NRET measurements performed on mixed, separately labeled DiC(12)AM terpolymers indicate the onset of association (C*) at similar to0.04 g/dL. Both NRET and steady shear viscosity studies indicate reorganization of the terpolymer network at pH values between 6.5 and 9.5, allowing for greater interaction of fluorescence labels and hydrophobes on separate chains.

Publication Title

Macromolecules

Volume

34

Issue

16

First Page

5579

Last Page

5586