Search

In the present study, three different block copolymers based on styrene, tert‐butyl methacrylate, and glycidyl methacrylate (GMA) were synthesized via sequential atom transfer radical polymerization. The addition of the GMA block was found to be best performed at 60°C. The polymers were then hydrolyzed and neutralized, to afford amphiphilic block copolymers, and the rheological properties of their aqueous solutions were measured, in order to investigate solution properties relevant for enhanced oil recovery, as a function of the polymer structure. It was observed that these polymers behave as thickening agents with shear thinning behavior. As expected, the polymers were sensitive to the presence of salt, as lower viscosities were recorded in saline water. However, the viscosity is less affected by high salinity, when compared to previously studied analogous diblock systems. In the best case, the viscosity only decreased by a factor of 1.8 upon salt addition whereas it decreased by a factor of 10 in previously reported non‐GMA containing polymers. Finally, thermo‐responsive behavior was found for one of the synthesized polymers. In particular, a hydrolyzed triblock poly[styrene‐b‐tert‐butyl methacrylate‐b‐glycidyl methacrylate], which synthesis is reported here for the first time, showed a thermothickening behavior, promising for the intended application in oil recovery. [ABSTRACT FROM AUTHOR]

Well-defined amphiphilic triblock poly(sodium methacrylate)-polystyrene-poly(sodium methacrylate) (PMAA-b-PS-b-PMAA) copolymers characterized by a different length of either the hydrophilic or the hydrophobic block have been synthesized by ATRP. In solution the micelle-like aggregates consist of a collapsed PS core surrounded by stretched charged PMAA chains. The micelles are kinetically 'frozen' and as a consequence the triblock copolymers do not show a significant surface activity. The hydrophilic block length has a major influence on the rheology, the shortest PMAA blocks yielding the strongest gels (at the same total weight concentration). The hydrophobic block length has only a minor influence until a certain threshold, below which the hydrophobic interactions are too weak resulting in weak gels. A mathematical model is used to describe the micelle radius and the results were in good agreement with the experimentally found radius in transmission electron microscopy. The influences of the ionic strength, pH and temperature on the rheology has also been investigated, showing the potential of these polymers as smart hydrogels. The change in conformation of the hydrophilic corona from the collapsed state to the stretched state by changing the pH was quantified with zeta-potential measurements. To the best of our knowledge, this is the first systematic investigation of this kind of triblock copolymers in terms of their rheological behavior in water. [ABSTRACT FROM AUTHOR]

ABSTRACT With the purpose of investigating new potential candidates for enhanced oil recovery (EOR), amphiphilic copolymers based on Poly(ethylene glycol) methyl ether acrylate (PEGA) have been prepared by Atom Transfer Radical Polymerization (ATRP). A P(PEGA) homopolymer, a block copolymer with styrene PS- b-P(PEGA), and an analogous terpolymer including also sodium methacrylate (MANa) in the poly(PEGA) (PPEGA) block, PS- b-P(PEGA- co-MANa) have been prepared and characterized. Viscosity and surface activity of solutions of the prepared polymers in pure and salty water have been measured and the results have been interpreted in terms of the chemical structures of the systems. A clear influence of the presence of the charged MANa moieties has been observed in both rheological and interfacial properties. The PS- b-P(PEGA- co-MANa) terpolymer, being an effective surface active viscosifying agent, is a good candidate as polymeric surfactant for applications in enhanced oil recovery and related. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44100. [ABSTRACT FROM AUTHOR]

Highlights: [•] Well-defined amphiphilic block copolymers have been prepared. [•] The prepared polymers form viscoelastic gels in water at low concentration. [•] The hydrophilic block length has a great influence on the solution rheology. [•] The aggregation number plays an important role in the gelation properties. [Copyright &y& Elsevier]

Threewell-defined polystyrene–poly(sodium methacrylate)amphiphilic block copolymers characterized by different moleculararchitecture (diblock, triblock, and four-arm star) have been synthesizedby ATRP. The rheology of their water solutions has been evaluatedby measuring dynamic moduli and shear viscosity at different concentrations.All polymers show remarkable thickening properties and a sol–geltransition at low concentration (0.1 wt %). Above the gel concentrationthe solutions are shear thinning without an apparent Newtonian plateau.The observed viscosity profile can be interpreted in terms of percolationtheory applied to highly stretched polymeric micelles, which startto contract above the percolation threshold. An interesting correlationbetween solution viscosity and concentration of hydrophilic block(defined here as “arm concentration”) has been observed,giving indirect evidence for the arrangement of the polymers intomicelles. The influence of ionic strength and pH on the rheology ofthese systems has also been preliminary investigated. [ABSTRACT FROM AUTHOR]

The study of interactions between polyelectrolytes (PE) and surfactants is of great interest for both fundamental and applied research. These mixtures can represent, for example, models of self-assembly and molecular organization in biological systems, but they are also relevant in industrial applications. Amphiphilic block polyelectrolytes represent an interesting class of PE, but their interactions with surfactants have not been extensively explored so far, most studies being restricted to non-associating PE. In this work, interactions between an anionic amphiphilic triblock polyelectrolyte and different types of surfactants bearing respectively negative, positive and no charge, are investigated via surface tension and solution rheology measurements for the first time. It is evidenced that the surfactants have different effects on viscosity and surface tension, depending on their charge type. Micellization of the surfactant is affected by the presence of the polymer in all cases; shear viscosity of polymer solutions decreases in presence of the same charge or nonionic surfactants, while the opposite charge surfactant causes precipitation. This study highlights the importance of the charge type, and the role of the associating hydrophobic block in the PE structure, on the solution behavior of the mixtures. Moreover, a possible interaction model is proposed, based on the obtained data. [ABSTRACT FROM AUTHOR]

Novel, multipurpose terpolymers based on styrene (PS), tert-butyl methacrylate (tBMA) and glycidyl methacrylate (GMA), have been synthesized via Atom Transfer Radical Polymerization (ATRP). Post-synthetic modification with 1-pyrenemethylamine (AMP) allows non-covalent functionalization of carbon nanotubes, eventually yielding a conductive nanocomposite materials capable of interacting with different Volatile Organic Compounds (VOCs) by electrical resistance variation upon exposure. Moreover, facile hydrolysis of the tBMA group yields polyelectrolytic macrosurfactants with remarkable thickening properties for promising applications in water solution, such as Enhanced Oil Recovery (EOR). [ABSTRACT FROM AUTHOR]