Synthesis of poly(benzyl glutamate-b-styrene) rod-coil block copolymers by dual initiation in one pot

We have developed a metal free synthetic pathway to homopolypeptide rod-coil block copolymers. The concept was proven for the synthesis of poly(benzyl-L-glutamate-b -styrene). A dual initiator containing a primary amine and a nitroxide group was used in a macroinitiation approach with high initiation efficiency. Good control over the molecular weight in the ring opening polymerization of benZyl-L-glutamate N-carboxyanhydride was obtained in DMF at 0 degrees C yielding poly(benzyl-L-glutamates) with low polydispersities around 1.1. The almost quantitative incorporation of the dual initiator was confirmed by MALDI-ToF analysis. Macroinitiation of styrene by nitroxide-mediated controlled radical polymerization yielded the block copolymer with high structural control. The diblock structure was confirmed by molecular weight increase upon macroinitiation by size exclusion chromatography and retention time comparison with homopolymers using gradient polymer elution chromatography. Both polymerizations were also successfully conducted in one pot without intermediate isolation owing to the high compatibility of both polymerization techniques. (C) 2008 Wiley Periodicals, Inc.