Effects of pairwise, self-associating functional side groups on polymer solubility, solution viscosity, and mist control

Abstract

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 regimebehavior 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.

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