According to Washburn et al. polymers from 1,2-disubstituted ethylenes with substituting groups larger than methyl groups are now polymerizable, just as thermodynamics would expect, just not in large amounts (yet).
Stumbling across this communication to macromolecules via sciencedaily.com, raging through the uni’s web interface to find a not-so-usable pubs.acs.org (errors in the HTML source code killed the menu for selecting the article… aaargh.), finally arriving at the paper: Macromolecules 2006, 39, 8210-8212 (doi:10.1021/ma061724j).
Although the polymerization of 1,2-substituted ethylenes is thermodynamically possible, in most cases there is a kinetic barrier which prevents these monomers from actually forming polymers or longer oligomers: the steric hindrance of the growing chain poses a greater challenge for chain growth than chain termination.
In this paper Washburn showed a simple — yet effective — method to actually discourage chain termination: a vapor deposition of the monomer into thin amorphous layers yields better kinetic prerequisites for polymerization. These monomer layers can then be polymerized in a photoinitiated radical chain growth polymerization.
This effect has been demonstrated with three different monomers: crotonitrile, fumaronitrile and cinnamyl alcohol.
Unfortunately this method has not yet been successful in producing enough material for analysis by NMR spectroscopy, but the created nanolayers have been analyzed by IR (Reflection Absorption Infrared Spectroscopy) and GPC.
It is always a major challenge to work against the detection limits of current methods. So thumbs up for further progress!
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