POLY 394 |
| The effect of a transoid or cisoid ester conformation in lactones has a pronounced effect on their reactivity in Novozym 435 catalyzed ROP. Moreover, the selectivity of Novozym 435 is also related to the conformation of the ester: cisoid lactones show S-selectivity while transoid lactones show a pronounced R-selectivity. The inability of Novozym 435 to polymerize 6-MeCL stems from its opposing selectivities for the alcohol and acyl-moiety. By combining Novozym 435 with a proper racemization catalyst, inactive alcohol chain ends in the S-configuration can be turned into active alcohol chain end of an R-configuration which can propagate. This combination of 2 different catalysts that work together to accomplish propagation, also referred to as iterative tandem catalysis, is the first example in which a racemic monomer can be completely turned into a homochiral polymer. |
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Biocatalysis in Polymer Science
1:30 PM-4:45 PM, Tuesday, 12 September 2006 San Francisco Marriott -- Salon 12/13, Oral
Division of Polymer Chemistry |