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Synthetic polymers are everywhere
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Synthetic polymers are Space Age materials. They're everywhere - from nylon fibres in clothes to reinforced plastics in canoes and skis. It's their chemical structure - chains from 100 to 1,000,000 atoms long - that gives polymers the valuable property of being able to form films and be easily shaped into objects.
World-wide research is in progress to develop new polymers and Canadian chemists are doing leading work in this field.
At the University of Toronto, chemistry professor Ian Manners' team has prepared a new class of inorganic polymers called "poly(thionylphosphazenes)" which consist of chains of phosphorus, nitrogen and sulphur atoms. These substances are attracting industrial interest because of their potential applications as high-performance elastomeric materials.
Dr Manners' group is also preparing photosensitive polymers based on elements such as silicon, boron, phosphorus, nickel and iron. They hope these new polymers will be useful for imaging applications.
Serendipity played a key role in the discovery of a new polymer by John Harrod's research team at McGill University. While investigating the reaction between compounds of titanium and silicon, the researchers found an unexpected gooey substance in the flask. Instead of disposing of the "unwanted" material, they - in collaboration with French chemist E Samuel - decided to characterize it. And they discovered that the new material was polymethylsilane
( [Si(CH3)H]n ). This is the best precursor yet known for the production of silicon carbide (SiC), an extremely hard ceramic compound used as crucible material for the manufacture of steel and also used as abrasives. Dr Harrod is now
collaborating with a chemist at the University of Michigan on the production of SiC fibres by this new method.
The design of new organic materials that will conduct charge when struck by light is the aim of Almeria Natansohn and her group at Queen's University. They are synthesizing new polymers with special electron donor groups. Some of the polymers are liquid crystals which self-assemble because of their charge-transfer interactions. As a result, Dr Natansohn expects to gather clues about how living systems self-organize.
Self-assembly is also the direction Jim Wuest and his students are exploring at the Université de Montréal. They have replaced the four hydrogen atoms in methane with special groups capable of hydrogen bonding. Amazingly, the molecules act as four-armed building blocks and associate into a three-dimensional diamond-like network. The beauty of this method, Dr Wuest says, is that specific structural or functional features can be formed by spontaneous self-assembly, not by tedious bond-by-bond synthesis.
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