Precisely defined polymer chains now a reality
Manufactured polymers are ubiquitous in our 21st Century lives. The large molecules – long chains of smaller molecules bonded together, form any synthetic clothing you might be wearing, rubbers and glues, and anything made of plastic.
However, the material properties exhibited by manmade polymers, rely on the sequence order taken by individual molecules making up the polymer chain. For example, a polymer chain made up of A, B, and C molecules could potentially take the form of A-B-C-B-A or A-C-A-B-B etc. Each different polymer could possess vastly different properties, which may or may not be of use to society.
Until now, material scientist have relied on mixing solutions, such as A, B, and C together, and witnessing the resultant polymer form — severely limiting the development of new materials.
Thanks to Hiroshima University researchers, we no longer need to rely on fate to determine such materiality. Professor Takeharu Haino and Dr. Takehiro Hirao from HU's department of Chemistry have developed a way to precisely define polymer-chain order — opening up the exciting potential of developing currently unimaginable materials.
Taking their cue from nature, where structurally well-defined biopolymers are the norm, e.g. in DNA and genes where slight variations to the order of a small number of organic molecules gives rise to the diverse spectrum of life, they have developed a self-sorting strategy that regulates the order molecules take when forming long chain polymers.
The new molecule linking process can be imagined as three distinct railway wagons, each possessing two unique couplers at either end that only permit them to be hitched in a particular order. When the correct order is achieved a train of unlimited length and complete regularity is possible.
In reality, three distinct monomer molecules were synthesized in the HU lab. Each one different from the other, they in turn each possessed two distinct bonding sites located at opposite ends of the molecules.
Solutions made up of these new molecules, mixed in stages, formed couplet solutions. Molecule 1 bonded with molecule 2 to form a solution made up of 1-2 molecules. Molecule 2 bonded with molecule 3 forming a 2-3 solution, and molecule 3 bonded with molecule 1 to form a 3-1 solution.
When these 1-2, 2-3, and 3-1 couplet molecules were then mixed in solution, they self-sorted to form a long chain polymer in the form of 1-2-3-1-2-3 etc. A regular polymer sequence that is predetermined and self-sorting.
This is a completely new way of making polymers. While previous synthetic polymers involved simple covalent bonding, where molecules shared electrons to bind them together, this system uses highly specific "grabber" ends on each molecule that bond with only one type of "pin" end on another molecule.
Professor Haino points out that the resulting polymer is not simply a molecule, but a molecular complex — a supermolecule. This new supermolecule production method completely and accurately predicts the makeup of the end product and can be manipulated and redesigned to give new manmade polymers with properties that could prove very useful for society.
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