Heat-responsive polymers that do not breakdown in water may lead to new antifouling coatings and enhanced oil recovery.
Thanks to the positively and negatively charged units in their monomers, zwitterionic polymers have a high affinity for water — a property known as hydrophilicity. This property helps prevent fouling, namely the build-up of contaminants. Current zwitterionic polymers are not effective in water as they use monomers such as commercially available acrylamide and methacrylates that tend to decompose and lose their electrostatic characteristics when wet.
Their high tolerance to salt, pH and temperature cause zwitterionic polymers to become viscous when subjected to high shear forces in brine, making them useful for marine antifouling applications.
To solve this issue, a team led by Vivek Vasantha from the A*STAR Institute of Chemical and Engineering Sciences in Singapore has now developed zwitterionic polymers based on water-stable monomers that incorporate nitrogen-containing derivatives known as imidazoles. The team introduced the zwitterions to readily accessible, hydrophobic polystyrene to boost its hydrophilicity in water by forming a hydration layer through electrostatic interactions and hydrogen bonding.
To synthesize the monomers, Vasantha’s team reacted styrene precursors with positively charged imidazoles before attaching the negatively charged sulfonate functional groups. The monomers produced polymers with intact zwitterionic properties, meaning that they retained their positive and negative charges.
These new imidazole-based polymers exhibited some novel solubility characteristics: unlike their conventional water-soluble counterparts, they swelled in water and dissolved only in highly concentrated brine. These differences stem from dipole–dipole interactions and the more hydrophobic nature of the new polymers compared to acrylamide and methacrylate.
With high tolerances to salt, pH and temperature, these polymers became increasingly viscous when subjected to higher shear forces in brine. This characteristic — similar to ‘silly putty’, which is malleable in one’s hands but is unchanged when hit with a hammer — makes the polymers attractive for enhanced oil recovery and marine antifouling coatings.
Another advantage of the new polymers is their reversible phase change: between 5 °C and 95 °C, the polymers formed gels that become clear fluids when heated above the so-called critical temperature in brine and that revert to their stable cloudy state on cooling.
“This phase transition results from the disruption of the equilibrium between salt, water and zwitterionic species,” says Vasantha. The polymer chains expand on heating and collapse below the critical temperature. The researchers can control the critical temperature by simply varying either the brine or polymer concentration. For example, the transition occurred at 20 °C at a low polymer concentration but at 40 °C at a higher polymer concentration.
“We are currently designing new zwitterionic polymers and copolymers with salt- and heat-responsive behavior for a wide range of applications, such as enhanced oil recovery, low-temperature protein separation and antifouling,” says Vasantha.
1. Vasantha, V. A., Jana, S., Parthiban, A. & Vancso, J. G. Water swelling, brine soluble imidazole-based zwitterionic polymers – synthesis and study of reversible UCST behavior and gel–sol transitions. Chemical Communications 50, 46–48 (2014).
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology
The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences