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Polymer chemistry.

The research work in our group centres on the design, the synthesis, and the chemical modification of polymers.

In one project, for example, we are testing ways of introducing useful functional groups into a simple commodity polymer such as poly(4-methylstyrene), thereby turning it into a more valuable reactive polymer. Our approach focuses on selectively converting the methyl groups on the polymer to hydroxymethyl or carboxylic acid groups. The major challenge in any such reaction on polymers lies in suppressing those side reactions that would either cleave the polymer chains, or cause them to crosslink. We have recently found that transition metal catalysts together with oxygen can be made to specifically oxidize a portion of the desired methyl groups to aldehyde, without changing the polymer chain length. A subsequent sodium borohydride reduction led to the polymer incorporating hydroxymethyl groups. We are currently extending this reaction to block copolymers of 4-methylstyrene in pursuit of new polymeric materials not easily produced in any other way. Some of these materials have foreseeable applications as reactive polymer membranes and films.

Another project studies the behaviour of polymers containing weak crosslinks. This work started with the concept that star-shaped polymers incorporating weak covalent bonds would, perhaps reversibly, dissociate at high temperatures or high-shear rates. Such polymers could be added in small amounts to lubricant oils, where they would modify the lubricant viscosity in response to changes in temperature and shear rate. Simpler polymers of this type are currently used industrially as lubricant additives for similar purposes. We are currently adapting bench-top anionic polymerization methods to prepare such reactive star-shaped polymers. In our third project we investigate a special type of polymeric separation media that incorporates chiral molecular cavities within the rigid polymer resin. These materials are prepared by polymerizing a monomer mixture containing enantiomerically pure amino acid complexes. This produces a rigid, crosslinked polymer matrix into which cavities reflecting the shape of the amino acid have become permanently imprinted. The monomers lining these cavities are designed to facilitate the chromatographic separation of amino acid racemates.

Most of the actual methods used in our research are borrowed from organic synthesis. They include purification of starting materials and intermediates by distillation and chromatography. We often chemically modify monomers and polymers using organic synthetic methods, often under a protective atmosphere. Even anionic and radically induced polymerization are organic (chain) reactions that are controlled by the chemical properties of monomers, solvent and initiator. We have a particular interest in carefully characterizing our products using NMR and infrared spectroscopy. In addition to these general methods we finally use a number of polymer specific techniques, in particular size exclusion chromatography to determine the molecular weight of soluble polymers.
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Author:Stover, Harald D.H.
Publication:Canadian Chemical News
Date:Apr 1, 1991
Words:447
Previous Article:Polymer colloids.
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