E. Zagar et M. Zigon, Solution properties of carboxylated polyurethanes and related ionomers in polar solvents (DMF and LiBr/DMF), POLYMER, 41(10), 2000, pp. 3513-3521
Solution properties of carboxylated polyurethanes (CPUs) and related ionome
rs (PUIs) in N,N-dimethylformamide (DMF) and DMF with added LiBr of differe
nt concentrations were investigated by size exclusion chromatography (SEC),
viscometry and in the case of CPUs also by SEC coupled with a multi-angle
light scattering detector (SEC-MALS). In DMF, both kinds of PUs have multim
odal molar mass distributions, while the reduced viscosity-concentration pr
ofiles indicate an upturn in very dilute regions usually related to the pol
yelectrolyte effect. However, SEC-MALS measurements of non-carboxylated PU
(NPU) and CPUs indicate that these PUs aggregate in DMF. After the addition
of LiBr to DMF unimodal molar mass distributions with much larger elution
volumes (V-c) and linear concentration dependences of reduced viscosity are
obtained for both kinds of PUs. LiBr in DMF not only screens the ionic gro
ups of carboxylated PUIs but also specifically interacts with the polar gro
ups of PUs. Thus, LiBr suppresses any electrostatic and/or molecular intera
ctions and consequently eliminates all the peculiarities encountered in SEC
characterization of both kinds of PUs in DMF. (C) 2000 Elsevier Science Lt
d, All rights reserved.