Researchers at Cornell are devising a method for creating new polymers in much the same way that a jewelry maker creates a beaded necklace 鈥 with the beads strung in a precise, controlled way.
The lab of , assistant professor of chemistry and chemical biology, has experimented in the past with creating 鈥渄esigner polymers鈥 using two photocatalysts. The process alternates the binding of sub-units (monomers), when either blue or green light was shown on them. The team has taken that approach to the next level in a paper just published in ACS Central Science.
For this work, Fors and colleagues used blue light to bind one type of monomer, and a chemical stimulus to connect the other. By toggling between the light or the chemical additive, and controlling how long the stimulus was applied, they could selectively choose which subunit was added to the growing polymer molecule 鈥 like beads on a necklace.
鈥淭he idea is, if you can precisely control polymer structure, then you should be able to control function,鈥 Fors said. 鈥淭hat鈥檚 really what we want to do 鈥 to be able to use external stimuli to have precise control over the monomer connectivity in the polymer backbone.鈥
Doctoral students Brian Peterson, Veronika Kottisch and Michael Supej, all from the Fors Lab, co-authored 鈥,鈥 published Aug. 8. ACS Central Science is an open-access journal of the American Chemical Society.
The group鈥檚 previous polymerization work had a key limitation: the ability to switch the polymerization process from one monomer to the other and back again, due to the two catalysts鈥 similar light-absorption properties, which made it impossible to completely shut off one reaction while the other was occurring.
The answer was a polymerization process that featured two different but compatible stimuli 鈥 in this case, light and a chemical oxidant.
鈥淭he challenge was finding stimuli that won鈥檛 interfere with one another,鈥 Supej said, 鈥渟uch that you promote the formation of one block while not polymerizing the other.鈥
The process was initiated by an oxidizing ferrocenium salt, which promoted the polymerization of the first monomer. Important was the ability to completely shut off that monomer鈥檚 polymerization while simultaneously stimulating the second, which the group was able to achieve via chemical reactions.
The resulting polymer exhibited high molecular weight and low dispersity, both desired properties in polymers.
Fors said this extension of the group鈥檚 previous polymerization work represents a major step forward. 鈥淲e showed in the past that we could switch polymerization mechanisms by just changing our external stimulus [light color],鈥 he said. 鈥淏ut it didn鈥檛 allow us to switch back and forth between monomers. This does.鈥
The monomers Fors and his group used in their di-block polymer, isobutyl vinyl ether and methyl acrylate, were chosen due to their reactivity and the group鈥檚 familiarity with those materials. In the future work, Fors鈥 group plans to employ new monomers and different types of stimuli, to create as-yet-undiscovered polymers.
鈥淚t鈥檚 almost impossible to find things that don鈥檛 involve polymers in everything you do on a daily basis,鈥 he said. 鈥淪o if we can even better control the polymer structure, we鈥檙e hoping that this is going to lead to some really big advances. It鈥檚 really kind of an enabling technology.鈥
This work was supported by grants from the National Science Foundation and by , provided by the Alfred P. Sloan Foundation.
This story also appeared in the
More News from A&S
Government
Social sciences
