Synthesis of Poly(benzyl glutamate-b-styrene) Rod-Coil Block Copolymers by Dual Initiation in One Pot RUTGER J. I. KNOOP, 1 GIJS J. M. HABRAKEN, 1 NICOLAS GOGIBUS, 1 SIMONE STEIG, 2 HENNING MENZEL, 2 COR E. KONING, 1 ANDREAS HEISE 1 1 Technische Universiteit Eindhoven; Den Dolech 2, P.O. Box 513, 5600 MB Eindhoven, The Netherlands 2 Technische Universita ¨t Braunschweig, Institut fu ¨ r Technische Chemie, Hans-Sommer-Str. 10, 38106 Braunschweig, Germany Received 2 November 2007; accepted 28 January 2008 DOI: 10.1002/pola.22648 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: 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-glu- tamate N-carboxyanhydride was obtained in DMF at 0 8C yielding poly(benzyl-L-glu- tamates) with low polydispersities around 1.1. The almost quantitative incorporation of the dual initiator was confirmed by MALDI-ToF analysis. Macroinitiation of sty- rene by nitroxide-mediated controlled radical polymerization yielded the block copoly- mer 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 intermedi- ate isolation owing to the high compatibility of both polymerization techniques. V V C 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3068–3077, 2008 Keywords: block copolymers; living radical polymerization; peptides; polypeptides INTRODUCTION Block copolymers are an important class of materials, which find use in a variety of applica- tions. Although synthetic procedures to obtain block copolymers vary in their detailed chemis- try, they usually follow two main strategies. One is the direct coupling of two blocks, which is of- ten associated with incomplete reaction and thus homopolymer impurities. More efficient is the synthesis via macroinitiation in which one block carries the initiator group for the polymer- ization of the second block. Particularly suited for this approach are controlled polymerization techniques as they usually allow good end-group control. Numerous block copolymers have been made by this approach combining virtually all types of polymerization techniques. One chal- lenge in this approach is to quantitatively intro- duce the initiator onto the first block, which of- ten requires a modification and purification step prior to the second polymerization. An elegant way to circumvent the modification step is to start with a bifunctional molecule having initiat- ing groups for both types of polymerization. This concept of dual or heterofunctional initiators has successfully been applied to the combination of numerous polymerization techniques. 1 Examples Correspondence to: A. Heise (E-mail: a.heise@tue.nl) Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 46, 3068–3077 (2008) V V C 2008 Wiley Periodicals, Inc. 3068