Control of the Reversible Shear-Induced Gelation of Amphiphilic Polymers through Their Chemical Structure

Abstract

This paper reports on the synthesis and characterization of a series of amphiphilic polymers which exhibit spectacular reversible shear-induced gelation in water. The systems consist of hydrophobically modified copolymers based on N,N-dimethylacrylamide and acrylic acid. The influence of molecular parameters such as the molecular weight and composition of the terpolymers on the rheological properties has been established. In the linear regime, the polymers behave like classical associating polymers: the sharp increase of the viscosity with concentration is the result of the transformation of intra-into intermolecular associations. Moreover, the dynamics of the physical gels obtained at high concentrations is tremendously slowed by the presence of alkyl side chains. Under shear the solutions display a Newtonian plateau at low shear rate followed by a shear-induced gelation. The latter is characterized in terms of a critical shear rate which sharply decreases as the polymer volume fraction increases. Thus, it appears that the shear-induced gelation may be controlled by adjusting the polymer molecular features. The networks built under shear closely behave like highly concentrated solutions at rest, suggesting a possible parallel between increasing shear and increasing concentration. This latter fact is reminiscent of the situation encountered with wormlike micelles. Shear flow could induce a transition between individual aggregates and a transient network as an increase in concentration does, thanks to the sharp modification of the electrostatic screening at the overlap concentration.

Rheology of associative polymer solutions

“…The statistical homologues of these copolymers have been considered by Cadix et al [102] and Wang et al [103] at much higher density of alkyl side chains. The presence of charges on the chains prevented phase separation.…”

“…For the system studied by the Cadix et al and Wang et al [102,103] the density of charges and hydrophobic groups varied in opposite ways. However, the number of charges and hydrophobic groups can also be varied in the same way by using polymerizable surfactants, as was shown by Gao et al [104,105] who copolymerized AM and sodium 2-acrylamido-tetradecane sulfonate.…”

pH-Responsive Hydrogel/Liposome Soft Nanocomposites For Tuning Drug Release

“…Such behavior is characteristic of a physical hydrogel consisting of strong physical bonds. 14, 49,50 Therefore, the addition of the liposomes affects the magnitude of moduli and not the overall viscoelastic behavior of the hydrogels, which remains predominantly elastic. It seems that the complex hydrogel strength was improved upon PC/Chol (1:1 mol/mol) liposome addition.…”

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.…”