What’s the way forward? Design new-generation polymers
In theory, these next-generation polymers could help mitigate pollution problems associated with plastic products. If the units were collected after unzipping to make new polymers, that would lead to chemical recycling. Most recycling done today simply involves melting the plastic and remoulding it.
“In my view, it has great potential; the problem is to make it cheap enough and to make the properties competitive enough to be useful and have market penetration for the consumer,” said Marc Hillmyer, who leads the Center for Sustainable Polymers at the University of Minnesota.
Economically, replacing the most widely used polymers like polyethylene (grocery bags), polypropylene (fishing nets) or polyterephthalate (single-use bottles) with unzipping polymers is not feasible.
Instead, scientists like Hillmyer are focusing on higher-value materials like the polyurethane foams (PUF) commonly found in mattresses and car seats.
In 2016, Hillmyer and his team made a polyurethane from unzipping polymers that was chemically recyclable. Molecular units derived from sugar linked up to make the polymers, which then cross-linked into polyurethane networks. The foam remains stable at room temperature but unzips into units if heated above 400 degrees Fahrenheit (204.4 degrees Celsius).
While waiting for these next-generation polymers to appear, current commercial plastics are still being pumped out on the scale of 400 million metric tonnes a year. And those plastics were intended to be as strong, as robust and to last as long as possible, Jeanette Garcia, a polymer chemist at IBM said. “Designing new polymers is going to be absolutely important and absolutely necessary.” But a bigger problem, she said, is learning how to break down legacy polymers of plastic waste in a similar way, ideally into their building blocks.