Chemists have spent the past century trying to make plastics break down in seawater. Most plastics take centuries to fully break down in the ocean. 【小题1】 However, this may change. Scientists have designed a new kind of plastic that can break down in seawater within weeks, not decades or more.

【小题2】 It is known as polylactide (聚乳酸) or PLA. It’s made by linking many building blocks into a long string. Scientists had hoped PLA would quickly break down in the environment. And in some places it does, but not in seawater. After three years in the ocean, LA remains largely unchanged.

Timo Rhein Berger is a PhD student at the University of Twente in the Netherlands. 【小题3】   For part of that work, he became part of a team that just added some biology-inspired breaking points to PLA. They put those breaking points to places where monomers (单体) in the PLA molecules are linked. Then, they soaked (浸泡) their samples in artificial seawater. In this way, they measured how fast the PLA broke down. As the team had hoped, seawater attacked the weakened links between monomers. That could tear the PLA chain apart. 【小题4】

When the researchers weakened 15% of PLA’s monomer links, the PLA broke down entirely within just two weeks. When they weakened only 3% of the links, the breakdown took about two years. 【小题5】 This can be achieved by adjusting how many weakened links it has.