THE FUNCTIONALITY OF ASSOCIATIVE POLYMER NETWORKS - THE ASSOCIATION BEHAVIOR OF HYDROPHOBICALLY-MODIFIED URETHANE-ETHOXYLATE (HEUR) ASSOCIATIVE POLYMERS IN AQUEOUS-SOLUTION

We re-examine the rheology of aqueous solutions of a hydrophobically m odified urethane ethoxylate associative polymer with M(n)=51000 contai ning C16H33 end groups. Fluorescence data indicate that association co mmences at a very low concentration (about 10 ppm). Over a wide range of concentrations, the system forms spherical flower-like micelles con sisting of about 10 looped chains. We determine the chain-end aggregat ion number to be 22 +/- 2 end groups per micelle, independent of polym er concentration. Analysis of the rheology data indicates that larger structures are formed through secondary aggregation of the polymer mic elles when the polymer concentration c(pol) > 0.2 wt.%. Treating the m icelles as the fundamental building blocks of the secondary associatio n, we calculate from the plateau modulus (at c(pol) > 1.2 wt.%) the ef fective functionality of the network and the fraction of chains that b ridge neighboring micelles. Both of these parameters increase as the c (pol) increases.