Copolymers of N-alkyl-and N-arylalkylacrylamides with acrylamide:influence of hydrophobic structure on associative properties.Part II:rheological behaviour in semi-dilute solution

摘要

BACKGROUND:Hydrophobically associating water-solubie polymers are of great interest because they possess unique rheological behaviour that results from the reversible association/dissociation process of their hydrophobic moieties.In this study,we focused on the structure of hydrophobic monomers related to the rheological and viscoelastic behaviours in semi-dilute solutions of acrylamide polymers modified with small amounts of N-alkyl-and N-arylalkylacrylamides(0.5 and 1 mol%).RESULTS:Associative efficiency increases with the length of the graft alkyl chain,with its proportion in the copolymer and with the presence of an aromatic group at the end of the alkyl graft chain.Introduction of hydrophobic groups induces a slowing down of the dynamics of the system,particularly marked for copolymers containing phenyldecyl chains.CONCLUSION:At low frequencies,solutions behave as Newtonian liquids;at higher frequencies,solutions of strongly associative systems behave as a solid with a storage modulus higher than the loss modulus and little dependency on the frequency.The system is a transient network whose dynamics depend on entanglements and hydrophobic associations.The presence of the hydrophobic groups induces an increase of the final relaxation time,even more pronounced since these associations are strong.