[Orestis]

I want to synthesize a diblock copolymer by ATRP. Initially i have synthesized the first block which has a bromide end group and then i use it as macroiniator for the polymerization of the second block. Since now i have tried different ligands (dnbpy, PMDETA) with copper salts (CuBr/CuCl) and the results are always the same. The main curve from GPC of the diblock copolymer is shifted towards lower elution times which means that the polymerization is activated but the main curve is BIMODAL in all cases. There is shoulder in lower elution times which broads the PDI. Any suggestions in order to control the polymerization and avoid the bimodal distributions? Thanks in advance