title: Interactions between brushlike polyacrylic acid side chains on a polyacrylate backbone in dioxane-water.
abstract: Densely grafted polyacrylic acids (d-PAAs) with overcrowded PAA side chains on the polyacrylate main chains were synthesized and characterized. Acryloyl poly(tert-butyl acrylate) macromonomer [M-P(tert-BA)] was prepared with a definite chain length (n=29) by atom-transfer radical polymerization (ATRP), then homopolymerization was carried out to produce densely grafted P(tert-BA)s with polyacrylate main chains of two different lengths (m=27 and 161). The two d-PAAs were obtained by hydrolyzing d-P(tert-BA)s in the presence of trifluoroacetic acid (TFA). The d-PAAs exhibit intermolecular and intramolecular hydrogen bonding between the carboxylic groups of PAA side chains in dioxane and pyridine; both were investigated using proton nuclear magnetic resonance (1H NMR) spectroscopy. The intermolecular hydrogen bonding was found to be dependent on polymer concentration, temperature, and water content. The intramolecular association between the PAA side chains was found to produce a contraction of the hydrodynamic volume of the d-PAA. Intermolecular hydrogen bonding produces aggregates, as demonstrated by dynamic light scattering (DLS). The clusters were found to shrink as the overall water concentration decreased, and this effect is tentatively explained by considering the gradient in chemical potential of water inside the clusters in comparison with the solvent phase.
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany.
authors.forename: Fengjun
authors.initials: F
authors.lastname: Hua
authors.forename: Rio
authors.initials: R
authors.lastname: Kita
authors.forename: Gerhard
authors.initials: G
authors.lastname: Wegner
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Meyer
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D002627:Chemistry, Physical / Q000379:methods; D004146:Dioxanes / Q000737:chemistry*; D006860:Hydrogen Bonding; D006868:Hydrolysis; D008027:Light; D009682:Magnetic Resonance Spectroscopy; D015233:Models, Statistical; D008970:Molecular Weight; D011108:Polymers / Q000737:chemistry; D011199:Potentiometry; D011522:Protons; D012542:Scattering, Radiation; D012997:Solvents; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014269:Trifluoroacetic Acid / Q000737:chemistry; D014867:Water / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; D004146:Dioxanes; D011108:Polymers; D011522:Protons; D012997:Solvents; D014867:Water; C006903:carbopol 940; D014269:Trifluoroacetic Acid