Rheological behavior of bigrafted hydrophobically modified polyelectrolyte
Résumé
The rheological behavior in 1 M NaCl obtained from the modification of sodium poly(acrylate), PAANa, with n-dodecyl (C12) and n-butyl (C4) side chains was studied. A series of mono- and bigrafted hydrophobically modified PAANa polymers with high weight-average molar masses were prepared through one-pot polymer postmodification, monografting with 2 mol % of long C12 alkyl groups and 2 and 10 mol % of short C4 alkyl groups and bigrafting with 2 mol % of C12 and 2 or 10 mol % of C4. Molar mass measurements show that no degradation of chain occurred during these reactions. H NMR was carried out at 85°C on the acidic form of the polymers, wherein the polymer microstructures were observed to agree well with the feed ratio. It was observed that for bigrafted copolymers, the C4-C12 modified polymers exhibit a similar trend as the C12 modified polymer, with an unexpected synergistic improvement of the viscosifying effect at low polymer concentrations and a strong decrease in intrinsic viscosity.