Rod-coil diblock polymerization from a bifunctional NMRP initiator

We have developed a universal synthetic pathway to rod-coil block copolymers. The concept was proven for the synthesis of poly(benzyl-L-glutamate-b-styrene). A dual initiator contg. a primary amine and a nitroxide group was used in a macroinitiation approach, thereby circumventing all polymer analogous reactions. Good control over the mol. wt. in the ring opening polymn. of benzyl-L-glutamate N-carboxyanhydride (NCA) was obtained in DMF at 0C yielding poly(benzyl-L-glutamates) with low polydispersities around 1.1. The almost quant. incorporation of the dual initiator was confirmed by MALDI-ToF anal. Macroinitiation of styrene by nitroxide mediated controlled radical polymn. (NMP) yielded the block copolymer. The block structure was confirmed by mol. wt. increase upon macroinitiation in size exclusion chromatog. (SEC) and retention time comparison with homopolymers using gradient polymer elution chromatog. (GPEC). While mainly diblock copolymers were obtained, small amts. of triblock copolymer due to radical coupling were also detected.