Poly(ammonium sulfopropylbetaine)s: 5. Interactions in dilute aqueous solution with low molecular weight salts or zwitterions and with poly(electrolyte)s

Abstract

Interactions in dilute aqueous solution at 25°C between atactic poly[diethyl-(2-methacryloyloxyethoxy-2-ethyl)-1-(3-sulfopropyl)ammonium betaine] (lateral group N +(CH 2) 3SO − 3 with dipole moment μ = 22.7 D) and a series of low and high molecular weight dipolar or ionic species were studied by viscometry and fluorescence. For constant additive concentrations (<1.5 M), the salt CH 3SO − 3, N +(C 2H 5) 4 is more efficient than the homologous zwitterions such as (C 2H 5) 3N +(CH 2) 3SO − 3 ( μ=22.7 D) or (C 2H 5) 3N +(CH 2) 2N(COCH 3)(CH 2) 3SO − 3 ( μ=28.9 D) for promoting the poly(zwitterion) chain expansion. Progressive increase of the concentration of the salt C 2H 5NH + 3, NO − 3 results first in a moderate poly(zwitterion) chain expansion followed by an asymptotic behaviour over a very broad concentration range from 0.75 up to 11M (pure liquid salt). At low concentration (<0.04 M) where the ammonium salts (CH 3) 4N +, X − (X − = Cl −, Br −) behave as inert additives, the corresponding poly(methacryloyloxyethyltrimethylammonium) halides interact with the poly(zwitterion) chain and lead to water-soluble interpolymer complexes of no definite stoichiometry and of very high viscosity: this binding is more efficient with Br − than with Cl −. The lack of any significant modification of the fluorescence emission wavelength and quantum yield (ΔФ ∼ 10%) in the same dansyl labelled poly(electrolyte) (X −= Cl −) shows that stacking of the two polymers over rather long blocks is very unlikely. However, poly(zwitterion)-poly(sodium acrylate) interactions lead to a hypsochromic shift of the emission wavelength of ∼ 15 nm.