Self - Assembly Of Surfactant Based On PH Response

Stimuli-responsive materials whose structure and properties vary with the change of the external environment, especially controllable viscosity ability of stimuli-responsive micelles, have great potential in the field of oil and gas development. Used by a stimuli-responsive surfactant molecules or counter ion, through molecular self-assembly method to prepare the stimuli-responsive micelles which have a controlled structure and performance. Analysising the change of non-covalent bonds in the stimulate response, have an important theoretical significance and use value.Using a pH-sensitive surfactants oleamide propyl tertiary amines (DOAPA) as the main agent, a pH response viscoelastic fluids has been prepared successfully. Studied various self-assembled structures at different pH values, find that the viscosity both been increased substantially at the pH0.2and pH6.8. By rheological tests, we indicate that both of the system have viscoelastic characteristics; then, using Cole-Cole diagram, found that the system does not meet the Maxwellian model at pH value of about0.2, and When the pH is about6.8, which is in line with the typical system Maxwellian model, indicating both solutions have different microstructures, the later is typically wormlike micellar structure. Proved by Cryo-TEM, the system belongs to vesicular structures at pH value of about0.2; the system belongs wormlike micelles at pH value of about6.8. DLS test showed that the average thermodynamically radius of the vesicle structure is14nm, the average thermodynamically radius of wormlike micelles was36.5nm. By switching tests proved that the electrostatic interaction is a major role in the formation of wormlike micelles. By the Infrared analysis results of pH6.82system proved hydrogen bond is a major role in the formation of vesicles. By rheological test analysised the influence of the chloride ion content and pH range to the rheological properties of wormlike micelles..Using a counter-ions, potassium hydrogen phthalate (PPA) with have a pH-responsive, with alkanes quaternary ammonium surfactants, successfully prepared a pH response viscoelastic fluid, which has to achieve prepared a pH stimulus response viscoelastic fluids by using common quaternary ammonium surfactants. By changing the pH value, founded that with the lengther carbon chain of the quaternary ammonium salt is, the broader pH value range of the thickening system has. By titration tests proved that PPA can be changed by adjustingthe pH value, when pH>5.5, PPA into dipotassium phthalate (DPPA), when pH<2.5, PPA into phthalic acid (PA), and analyzed the different forces in the systerm. Through the rheological fluid tests of three states of PPA as a counter ion show that systems have viscoelastic characteristics when PPA as a counter ion; only the longer carbon chain quaternary system has sticky elastic characteristics, when PA as a counter ion; bothe system have not a viscoelastic characteristics when DPPA as the counter ion; using Cole-Cole diagram found viscoelastic fluids are typically formed in line Maxwellian model. By Cryo-TEM proofed that, the system belongs to a spherical micellar structure when DPPA as a counter ion. DLS test showed that the average thermodynamics radius of spherical micelles is about1.33nm, an average thermodynamics radius of wormlike micelles is about25nm. The visco-elastic fluid by PA, through a temperature sensitivity test, indicating system has a temperature-responsive.