title: The synergistic effect between hydrophobic and electrostatic interactions in the uptake of amino acids by strongly acidic cation-exchange resins.
abstract: The goal of this work was to investigate the synergistic effect between the electrostatic and hydrophobic interactions upon the uptake of organic ions with hydrophobic moieties by ion-exchange resins with hydrophobic matrixes. The uptake of neutral amino acids by a macroporous polystyrene-based strongly acidic cation-exchange resin (D001) and two strongly acidic cation-exchange resins (poly(2-acrylamido-2-methyl propanesulfonic acid) and poly(vinylsulfonic acid)) with much less hydrophobic matrixes essentially follow an ion exchange stoichiometry. However, the thermodynamic parameters of the uptakes indicate that besides electrostatic interaction, hydrophobic interaction also contributes to the affinity of the amino acids with hydrophobic side chains for D001. No detectable uptake capacities for the amino acids by D001AM, which was obtained by amidation of the sulfonic acid groups of D001, can be determined. Thus, it is deduced that the hydrophobic interaction alone contributes little to the uptake of these amino acids by D001, of which hydrophobicity is the same with or lower than that of D001AM. These results indicate that synergistic effect exists between the electrostatic and hydrophobic interactions when the two interactions exist in a chelate manner and the hydrophobic interaction contributes to the uptake even if the hydrophobic interaction is so weak that it contributes little to the uptake when it acts alone.
authors.affiliation: Key Laboratory of Functional Polymer Materials, Ministry of Education, Institute of Polymer Chemistry, Nankai University, Tianjin 300071, China.
authors.forename: Shaoling
authors.initials: S
authors.lastname: Cheng
authors.forename: Husheng
authors.initials: H
authors.lastname: Yan
authors.forename: Changqing
authors.initials: C
authors.lastname: Zhao
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D007475:Ion Exchange Resins / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D011137:Polystyrenes / Q000737:chemistry; D011145:Polyvinyls / Q000737:chemistry; D055672:Static Electricity; D013451:Sulfonic Acids / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D000596:Amino Acids; D007475:Ion Exchange Resins; D011108:Polymers; D011137:Polystyrenes; D011145:Polyvinyls; D013451:Sulfonic Acids; C432006:divinylbenzene-polystyrene copolymer; C008959:lyapolate; C077118:poly(2-acrylamido-2-methyl-1-propanesulfonic acid)