Plastics and natural materials such as DNA, proteins, and cellulose are linked by one key idea: they are polymers, long chains of repeating units connected much like beads on a string.
Chemical bonds between the individual units hold these polymers together. In plastics, strong bonds make the material difficult to break down. This durability is useful while a plastic product is in use, but once it is discarded, it can create serious problems for ecosystems and wildlife.
Making breakdown programmable
Scientists at Rutgers University have explored a new approach: making plastic breakdown programmable. In other words, they experimented with plastics that could perform as usual while in use but break down more easily after a chosen amount of time.
To create these plastics, the scientists arranged parts of the plastic’s chemical structure into specific positions that, when triggered, would cause the material to break down. Like folding a piece of paper so that it tears along the crease, the design allows the plastic to split at these “pre-folds” after a set amount of time.
By changing the spatial positions and orientations of these parts, the scientists could engineer the plastic to break down after different lengths of time, ranging from days to years. Importantly, the plastic could still maintain its original strength and durability while it was being used.
Different lifetimes for different uses
These plastics are especially useful because they do not require harmful chemicals or high heat to break down. Their adjustable lifetimes also mean that they could work in many applications, from food packaging that may need to last only one day to automobile parts that need to last several years.
They could even be used in coatings for timed drug-delivery capsules, which dissolve after a specific amount of time.
Although the scientists have found that the liquids produced during breakdown are not harmful in their tests, thorough testing is still needed before programmable plastics can be widely implemented. The researchers are optimistic that this approach to sustainability could eventually reach consumers.