Macromolecules, Vol.42, No.4, 1380-1391, 2009
Effects of Pairwise, Self-Associating Functional Side Groups on Polymer Solubility, Solution Viscosity, and Mist Control
Solution properties are reported for homologous series of narrowly distributed polymers with systematically varied content of self-associating groups. Anionically polymerized polybutadienes of two lengths (510 and 1250 kg/mol) serve as prepolymers that are modified by incorporation of carboxylic acid side groups using thiol-ene coupling to pendant vinyl groups. Carboxylic acid groups strongly reduce polymer solubility in hydrocarbon solvents, restricting the extent of functionalization that can be examined in single-phase solutions (e.g., in chlorododecane, functionalization must be kept < 1.8 mol% even for the shorter of the two backbones). In the single-phase regime, addition of hydrogen bond "stickers" weakly affects solution viscosity. Even at concentrations that produce overlap at the scale of strand length between stickers, viscosity increases are less than 1 order of magnitude. These controlled studies (Using functionalized and unmodified polymer homologues of matched, well-defined length) challenge the pre-existing understanding of the rheology of self-associating polymers. The results indicate that effects of intrachain pairing are important beyond the dilute regime-behavior unaccounted for in earlier experimental and theoretical studies. The implications for mist control of aviation fuel are that self-associating polymers of acceptable solubility in the fuel are not superior to nonassociating polymers even at concentrations several times above overlap.