Rheological properties of multisticker associative polyelectrolytes in semidilute aqueous solutions

Abstract

Multisticker associative polyelectrolytes of acrylamide (Ϸ86 mol %) and sodium 2-acrylamido-2-methylpropanesulfonate (Ϸ12 mol %), hydrophobically modified with N,N-dihexylacrylamide groups (Ϸ2 mol %), were prepared with a micellar radical polymerization technique. This process led to multiblock polymers in which the length of the hydrophobic blocks could be controlled through variations in the surfactant-tohydrophobe molar ratio, that is, the number of hydrophobes per micelle (N H ). The rheological behavior of aqueous solutions of polymers with the same molecular weight and the same composition but with two different hydrophobic block lengths (N H ϭ 7 or 3 monomer units per block) was investigated as a function of the polymer concentration with steady-flow, creep, and oscillatory experiments. The critical concentration at the onset of the viscosity enhancement decreased as the length of the hydrophobic segments in the polymers increased. Also, an increase in the N H value significantly enhanced the thickening ability of the polymers and affected the structure of the transient network.In the semidilute unentangled regime, the behavior of the polymer with long hydrophobic segments (N H ϭ 7) was studied in detail. The results were well explained by the sticky Rouse theory of associative polymer dynamics. Finally, the viscosity decreased with an increase in the temperature, mainly because of a lowering of the sample relaxation time.

Hydrodynamic properties of some cationic amphiphilic polysaccharides in dilute and semi-dilute aqueous solutions

“…The power law in the entangled regime (n 3 ) overcomes in some cases the value of 3.75 predicted by theory for both neutral and charged polymers (Dobrynin et al, 1995). This strong concentration dependence of Á sp , characteristic to associative polymers and consistent with the sticky reptation model developed by Rubinstein and Semenov (2001), was experimentally observed for other hydrophobically modified polyelectrolytes (Di Cola et al, 2004;Kujawa et al, 2006). This shows that the presence of a few long hydrophobic chains determines a more rapid entanglement of the polymer chains, which favors the inter-molecular hydrophobic interactions (or vice-versa: the intermolecular hydrophobic associations favor the chain entanglement).…”

Self-Healing Hydrogels Formed via Hydrophobic Interactions

“…Because incorporation of a small amount of hydrophobic groups in a hydrophilic polymer backbone results in polymers with extraordinary rheological properties in aqueous solutions, many studies have been carried out during the past two decades on the synthesis and solution properties of hydrophobically modified hydrophilic polymers [54,55]. Candau and coworkers investigated the preparation and rheological behavior of polyacrylamides (PAAms) modified with various amounts of N-alkyl-or N,N-dialkylacrylamides of various alkyl-chain lengths [51][52][53][54][56][57][58]. The zero-shear viscosity of semidilute solutions of hydrophobically modified polymers significantly increases as the number of hydrophobes per block (N H ) or the number of blocks per chain (S n ) is increased [52,56,57].…”

“…Candau and coworkers investigated the preparation and rheological behavior of polyacrylamides (PAAms) modified with various amounts of N-alkyl-or N,N-dialkylacrylamides of various alkyl-chain lengths [51][52][53][54][56][57][58]. The zero-shear viscosity of semidilute solutions of hydrophobically modified polymers significantly increases as the number of hydrophobes per block (N H ) or the number of blocks per chain (S n ) is increased [52,56,57]. Hydrophobically modified PAAms are of great interest due to their possible application areas, including oil recovery and paints.…”

Hydrophobically Modified Sulfonated Polyacrylamides for IOR: Correlations between Associative Behavior and Injectivity in the Diluted Regime

“…Various techniques have been implemented among which viscosimetry [4][5][6][7][8][9][10][11][12], fluorescence [13][14][15][16], transmission, scanning and environmental scanning electron microscopy (TEM, SEM and ESEM) [16][17][18], 19 F NMR spectroscopy [19,20], neutron scattering [21][22][23][24] and Static and Dynamic Light Scattering (SLS and DLS) [14][15][16][25][26][27][28][29][30][31][32][33][34][35][36][37]. Theoretical approaches have also been proposed to describe HMWSP static [38,39] and dynamic [40] properties.…”