Polymers, large molecules made up of repeats of smaller molecules called monomers, are found in almost everything we use in our daily lives. Polymers can be natural or synthetically created. Natural polymers, also called biopolymers, include DNA, proteins, and materials like silk, gelatin, and collagen. Synthetic polymers make up many different types of materials, including plastic, which are used in the construction of everything from toys to industrial fiber cables to brake pads.
As polymers are formed by a process called polymerization, the monomers are linked by a chain. As the chain grows, the structure of the polymer determines its unique physical and chemical properties. Researchers are continually studying polymers, how they form, how they are structured, and how they develop these unique properties. By understanding this information, scientists can develop new uses for polymers and create new materials that can be used in a wide variety of industries.
In a published article in Nature Communicationthe researchers describe a new structure found in an aqueous solution of an amphiphilic copolymer, called bilayer-folded lamellar mesophase, which was discovered through a random copolymer sequence.
“A new mesophase is an important finding because it shows a new way for molecules to self-organize,” said Professor Myungeun Seo from KAIST’s Department of Chemistry. “We were particularly excited to identify this bilayer-folded lamellar phase because pure bilayer membranes are difficult to thermodynamically bend.”
The researchers believe that this mesophase structure comes from the linking of monomers within the copolymer. How the different monomers arrange themselves in the chain that makes up a copolymer is important and can have implications for what the copolymer can do. Many copolymers are random, which means that their structure depends on how the monomers interact with each other. In this case, the interaction between the hydrophobic monomers associates the chains of the copolymer to conceal the hydrophobic domain from water. As the structure becomes more complex, the researchers found that a visible order develops so that the monomers can be matched to the correct pair.
“While we tend to think of disorder as meaning random, here we showed that periodic order can arise spontaneously from the sequence of random copolymers based on their collective behavior,” Seo said. “We believe this stems from the sequence-matching problem: finding a perfectly complementary pair for a long sequence is nearly impossible.”
This is what creates the unique structure of this newly discovered mesophase. The copolymer folds spontaneously and creates a water-separated multilamellar structure. A multilamellar structure refers to plate-like folds and the folded layers stack on top of each other. The resulting mesophase is birefringent, meaning light refracts through it, it is similar to liquid crystal, and viscoelastic, meaning it is both viscous and elastic.
Looking forward, researchers hope to learn more about this new mesophase and understand how to control the outcome. Once the mesophase and how it forms are better understood, it is possible that new mesophases will be discovered as new sequences are searched for. “One of the obvious questions for us is how to control the bend frequency and adjust the bent height, which is what we are currently working on. Ultimately, we want to understand how different multinary sequences can associate with each other. others to create order and apply knowledge to develop new materials,” Seo said. Korea’s National Research Foundation, Ministry of Education, and Ministry of Science and ICT funded this research.
– This press release was originally published on the Korea Higher Institute of Science and Technology website