Rheological Studies Of Polymer/surfactant Solutions

Surfactants and polymers which have the particular properties have been applied in biology, materials synthesis, energy and various modern science and technology. The mixtures of them possess some intriguing and fascinating features, which surfactant or polymer alone does not have. Therefore, they have been used in oil extraction, cosmetic, materials synthesis and pharmaceutical etc. The investigation of the interaction between them has also been attracted much attention. They spread widely and go deep into the level of molecular and sub-molecular. Although the mechanism of the interaction between them has been recognized as rationalization, but some details are not fully understood yet.In the present work, the rheological behaviors of SDS/cationic guar solution, the effect of NaCl and ethanol on the rheological behaviors of SDS/cationic guar solution, the reological behaviors of KOA/cationic guar solution, the influence of NaCl and CTAB on the sol-gel transition of MC and the influence of nonionic polymers on the rheological behaviors of KOA/Na2CO3 system have been investigated. The main results are listed as follows:1. When the concentration of SDS approaches 0.08wt%, the zero viscosity of cationic guar solution increases significantly upon addition of SDS. In particular, a viscosity enhancement is observed to be almost 3 orders of magnitude as SDS increases from 0 to 0.043 wt%. The zero viscosity is exponential with the concentration of SDS. The storage modulus G′and the loss modulus G″of the cationic guar solution also increase significantly upon addition of SDS. The Maxwell model can not be used to describe the cationic guar/SDS mixture. The Cox-Merz rule is not applicable for the mixture. The complex viscosityη* is lower than the dynamic viscosityη(γ) at some shear rates. The higher concentration of SDS in cationic guar solution, the lower frequency at which the discrepancy betweenη* andη(γ) begin to be onset. Gc which is the G′at the crossover point of G′and G″is almost independent of the concentration of SDS, indicating the number of the cross-links is less changed by the addition of SDS. The relaxation timeτc which indicates the strength of the cross-links increases swiftly with the increase of SDS concentration. With the increase of temperature, the zero viscosity, G′, G″,τc decrease gradually, while Gc is less changed. The flow activation energy Ea which is calculated from the Arrhenius formula increase with the increase of SDS concentration.2. Similar to SDS, the zero viscosity, G′, G″of cationic guar solution also increases significantly with the addition of KOA. But the concentration at which the zero viscosity of cationic guar solution begins to increase of SDS is lower than KOA. Furthermore, we also find that the phase separation does not appear even when the concentration of KOA is larger than its CMC, while SDS causes the phase separation of cationic guar at the concentration far below its CMC. In the scope of the sweep frequency the G′and G″of the cationic guar/SDS mixture is higher than the cationic guar/KOA mixture at the same surfactant concentration, but the relaxation time of the cationic guar/KOA mixture is higher than the cationic guar/SDS mixture. For the cationic guar/KOA mixture, Gc decreases with the increase of the KOA concentration, butτc increases. With the increase of temperature, the zero viscosity, G′, G″,τc of the cationic guar/KOA mixture also decrease gradually, while Gc increases. At the same surfactant concentration the flow activation energy Ea of the cationic guar/KOA mixture is higher than the cationic guar/SDS mixture.3. The zero viscosity, G′, G″of the cationic guar/SDS mixture all decrease with the addition of NaCl or ethanol, while their influences on the Gc,τc of the mixture are different. With the increase of NaCl concentration the Gc,τc of the mixture decrease. But the Gc of the mixture is almost unchanged andτc decrease with the increase of ethanol concentration.4. The sol-gel behavior of MC is sensitive to the existence of NaCl, CTAB or their mixture. The sol-gel temperature of MC decreases linearly with the increase of NaCl concentration, but increases linearly with the addition of CTAB. When NaCl concentration is fixed at 3wt% the sol-gel temperature of MC keeps almost at the same value which is higher than the calculated value with the increase of CTAB concentration. While at the fixed CTAB concentration (0.2wt%) the sol-gel temperature of MC decreases linearly with the increase of NaCl concentration. The slope of the line almost equals to the value of the line without the CTAB. Compared to the experimental value with the calculated value of sol-gel temperature of MC at the fixed CTAB concentration (0.2wt%) and different NaCl concentration, we find that when the concentration of NaCl is lower than 3.3wt%, the experimental value is higher than calculated value, while the trend reverses when the concentration of NaCl is higher than 3.3wt%. 5. The solution of 3wt% KOA in the presence of 3.7wt%Na2CO3 shows viscoelastic and non-Newtonian fluid properties. The viscoelastic behavior of the solution can be described by the Maxwell mode at low sweep frequency but there are some deviations at high sweep frequency. The addition of PVP, PEG, PPG all induce the transition of the solution from non-Newtonian fluid to Newtonian and the enormous drop of the zero viscosity of the solution. The effects of these polymers in inducing this transition follow this trend: PVP> PEG> PPG. The trend is different from that for CTAB/NaSal solution and that obtained from the interactions of anionic surfactants and nonionic polymers at low anionic surfactants concentration.