Production of biocompatible and super-absorbent materials may become easier, thanks to Anbanandam Parthiban and co-workers at the A*STAR Institute of Chemical and Engineering Sciences.
Using a modification to the high-precision technique known as atom transfer radical polymerization (ATRP), which links molecules into long chains, the researchers have developed new compounds that can directly polymerize acidic vinyl monomers, such as acrylic acid. Acrylic acid polymers are water-absorbing materials widely used in diapers and as emulsifying agents for pharmaceuticals and cosmetics.
Previous attempts to use ATRP with polar vinyl monomers, including acrylic acid, were unsuccessful, a failure that some chemists attributed to catalyst ‘poisoning’ by carboxylic acids. Parthiban and his team’s compounds resolve this problem by binding to the catalyst while simultaneously initiating the radical polymerization process. This process prevents poisoning and dramatically reduces metallic waste.
Despite ATRP’s inability to directly produce acrylic acid polymers, it is used in laboratories worldwide: it allows researchers to assemble complex polymers in a step-by-step fashion that gives enormous control over product architectures. The key is using a catalyst that can readily switch between two oxidation states, such as a copper salt, explains Parthiban. The copper catalyst first interacts with an ATRP initiator molecule to activate organic free radicals and an oxidized metal complex. The free radicals then quickly polymerize target monomers, while the metal complex undergoes equilibrium with a dormant, lower oxidation state. With appropriate reaction conditions, chemists can then restart polymerization with new monomers.
Parthiban and co-workers addressed ATRP’s limitation by developing ‘unimolecular ligand–initiator systems’ (ULIS), a series of branched molecules containing multiple binding sites for copper atoms, as well as halogens for activating free radical species. In this approach, the ULIS molecules become part of the polymer chain during the active–dormant cycles instead of remaining isolated. The researchers envisaged that this interconnection would suppress the acidic side-reactions that lead to catalyst poisoning.
Experiments by the researchers proved their theories correct: they could efficiently polymerize acrylic acid and other vinyl monomers using ULIS-promoted ATRP (see image). Surprisingly, they found that these reactions could be achieved using less than 100 parts-per-million concentrations of copper catalyst, a quantity comparable to residues left in conventional ATRP purified polymers.
Parthiban notes that although the ULIS ligands are part of the polymer chain and might be expected to produce high amounts of metal waste, the homogenous nature of intramolecular-based free radical polymerization allows less metal to be used — an important consequence for sustainable chemistry efforts.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Chemical and Engineering Sciences
Jana, S., Parthiban, A. & Choo, F. M. Unimolecular ligand–initiator dual functional systems (ULIS) for low copper ATRP of vinyl monomers including acrylic/methacrylic acids. Chemical Communications 48, 4256–4258 (2012).
Further Reports about: acrylic acid > ATRP > chemical engineering > dual-function molecules > Engineering Sciences > free radicals > Polymere > polymerize acidic vinyl monomers > radical polymerization process > super-absorbent materials
More articles from Life Sciences:
ASU researchers discover chameleons use colorful language to communicate
12.12.2013 | Arizona State University
Sleep-deprived mice show connections among lack of shut-eye, diabetes, age
12.12.2013 | University of Pennsylvania School of Medicine
A unique solar panel design made with a new ceramic material points the way to potentially providing sustainable power cheaper, more efficiently, and requiring less manufacturing time.
It also reaches a four-decade-old goal of discovering a bulk photovoltaic material that can harness energy from visible and infrared light, not just ultraviolet light.
Scaling up this new design from its tablet-size prototype to a full-size solar panel would be a large step toward making solar power affordable compared with ...
Atlantische Flohkrebse pflanzen sich jetzt auch in arktischen Gewässern fort
Biologen des Alfred-Wegener-Institutes, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), haben zum ersten Mal nachgewiesen, dass sich in den arktischen Gewässern westlich Spitzbergens auch Flohkrebse aus dem wärmeren Atlantik fortpflanzen.
Diese überraschende Entdeckung deute auf einen möglichen Wandel der arktischen Zooplankton-Gemeinschaft hin, berichten die Wissenschaftler und Wissenschaftlerinnen in der Fachzeitschrift Marine Ecology ...
The molecular architecture of three key proteins and their complexes reveals how plants fine-tune their immune response to pathogens
Plants rarely get sick in their natural environment. When the threat of infection arises, a quick decision is made about the necessary countermeasures. The course is set by a protein which forms complexes with its partner proteins for this purpose.
Jane Parker from the Max Planck Institute for Plant Breeding ...
Researchers studying speciation of butterfly orchids on the Azores have been startled to discover that the answer to a long-debated question "Do the islands support one species or two species?" is actually "three species".
Hochstetter's Butterfly-orchid, newly recognized following application of a battery of scientific techniques and reveling in a complex taxonomic history worthy of Sherlock Holmes, is arguably Europe's rarest orchid species. Under threat in its mountain-top retreat, the orchid urgently requires conservation recognition.
A lavishly illustrated publication, titled "Systematic revision of Platanthera in ...
Researchers from Brown University and the University of Hawaii have found some mineralogical surprises in the Moon's largest impact crater.
Data from the Moon Mineralogy Mapper that flew aboard India's Chandrayaan-1 lunar orbiter shows a diverse mineralogy in the subsurface of the giant South Pole Aitken basin.
The differing mineral signatures could be reflective of the minerals dredged up at the time of the giant impact 4 billion years ago, ...
12.12.2013 | Life Sciences
12.12.2013 | Earth Sciences
12.12.2013 | Studies and Analyses
11.12.2013 | Event News
10.12.2013 | Event News
05.12.2013 | Event News