As we know, plastic and rubber litter is produced incessantly, and due to inefficient solid waste management, these wastes keep accumulating in places close to our cities from where they are also washed by runoff into our waters. This situation may not worry most people, who make irrational use of this resource, but many scientists are committed to finding an alternative to remedy this problem; among them, a research group from Priceton's chemistry department seems to have found a molecule that would be a breakthrough towards closed-loop recycling of plastic waste.
New molecule could give us a new route to recyclable plastics. Image credit: pixabay.com.
This research team has just published its finding in the journal Nature Chemistry, the discovery of a new molecule of polybutadiene, which during its polymerization produces (1,n'-divinyl)oligocyclobutane, a molecule that is chained in a repetitive sequence giving rise to a telechelic microstructure that presents a high crystallinity even at low molecular weight, something not obtained before, and that allows the process to be reversed.
That is, this butadiene can be polymerized to make a new plastic, which can then be depolymerized back into the monomer to be reused.
The molecule is chained into a structure that had not been obtained before. Image designed by 
Although this research is still at an early stage, it has set a great precedent for the chemical transformation and utilization of plastics. Although the depolymerization process is not new, it is not considered practical for most materials, as it requires very specialized polymers and a series of complicated steps, which makes the process prohibitively expensive, so it is only used in certain market niches. But with this process, a very common feedstock could be used, the one used to make polybutadiene is in fact one of the world's leading petrochemicals, used in the manufacture of plastic and synthetic rubber.
A major step in the research was the development of an iron catalyst, which proved very useful in the polymerization of butadiene monomers to form oligocyclobutane. A molecule that adopted a very unusual square structure, since usually the chaining of polymers results in a long S-shaped structure.
Then, for depolymerization, the oligocyclobutane is subjected to vacuum in the presence of the pyridine iron catalyst used to synthesize it, this produces desoligomerization to regenerate the starting monomer, demonstrating a rare example of closed-loop recycling of a hydrocarbon-derived material.
This research is a big step towards a more efficient recycling of plastic products, basically they have taken a very common material in the manufacture of conventional plastics, and through a new process have transformed it into a completely new material whose special feature is its easy depolymerization, i.e. its reconversion to a raw material easy to use again. This is a great advantage for obtaining a recyclable plastic, whose reconversion process is energetically almost the same as the monomer production process, which makes the process very attractive given that for most single-use plastics, recovering the monomer is such an energetically costly process that it is unrealistic, which is why most plastic bags and products end up in landfills.
This shows us that with chemistry it is sometimes enough to change the way we manufacture objects to give them a new use or make them less hazardous to the environment.
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