Synthesis of thiol-derivatized initiators for nitroxide-mediated radical polymerization: Reversible disulfide formation

New N-alkoxyamine initiators were synthesized containing the highly versatile thiol group. A tert-butyldimethylsilyl protected monodirectional initiator was synthesized as well as a disulfide linked bidirectional initiator. Both initiators were used in nitroxide-mediated radical polymerization with styrene; additionally, the disulfide bidirectional initiator was used to polymerize dimethylacrylamide. Polymer chains bearing a terminal silyl protected thiol were deprotected and oxidized, resulting in polymers with double the molecular weight. Alternately, polymers grown from the bidirectional initiator bearing a central disulfide linkage were reductively cleaved, resulting in a halving of molecular weight. The manipulation of the thiol group and the reversible disulfide linkage at the polymer terminus offers potential for applications in nanotechnology.