Plastic materials can be damaged when they are processed or recycled. The materials are less durable when they are broken inside the recycling processes. Soft materials that can self-heal are one way that plastic can be made more sustainable.
The self-assembled materials can recover their strength after being damaged. Many researchers are looking at applications of self-healing materials where plastic components are difficult to replace or repair. Scientists don't have a good understanding of their behavior at the atomic level.
O'Connor is working to change that. A group of people are using simulations to study a type of self-assembling material. These are made of long chains that are sticky.
The sticky groups attract each other and form clusters that connect different chains together into a network that looks like a bowl of noodles. The sticky clusters can heal the material if they are damaged. If the sticky interactions become too strong, very large clusters will form, and thepolymer will become too rigid to manipulate.
O'Connor created a simulation of the behavior of the polymers during the stretching process. The sticky clusters inside the material didn't react in a uniform way when he stretched them.
The strongest clusters were able to break up and allow chains to flow, while the weakest clusters were unable to do so. The heterogeneous response helps explain why materials are so unpredictable during manufacturing.
The way you write a theory for a material is to ask what the average response of the polymer chains will be to what you are doing. O'Connor gave an explanation. There are two different behaviors happening with this network. Some chains are collapsing. The average won't be captured either.
When O'Connor accelerated the simulation to stretch the chains more quickly, he found that they all behaved the same.
The clusters that acted as permanent connections broke apart and formed many smaller clusters with similar properties to the smaller clusters already in existence. O'Connor said that all hope is not lost for working with, processing, and one day recycling self- assembled materials. The way the system breaks up creates a kind of self-organization because of the messiness. When we can more carefully control them, I will be interested in what they will do.
O'Connor's team can use simulations to control the size and stickiness of the clusters and to evaluate how more carefully architected networks will respond to the flow. The future of processing self-assembled materials can be traced back to this research.
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