Iron Tris(bipyridine)-Centered Star Block Copolymers: Chelation of Triblock Macroligands Generated by ROP and ATRP

Abstract

A series of bipyridine (bpy)-centered triblock copolymers, BA-bpy-AB, were generated by ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP) mechanisms. Hydroxyl chain ends of poly(ε-caprolactone) (PCL) and poly(lactic acid) (PLA) precursors, bpyPCL2 and bpyPLA2, respectively, were converted to α-bromoesters for use as macroinitiators for the subsequent addition of second blocks, poly(methyl methacrylate) (PMMA) or poly(tert-butyl acrylate) (PtBA). Materials formed by sequential ATRP reactions, bpy(PMMA-PS)2 and bpy(PS-PMMA)2, were also produced. New [Fe(bpy(AB)2)3]2+ analogues were formed by combination of triblock macroligands with [Fe(OH2)6](BF4)2 in 3:1 CH2Cl2:MeOH solutions. For bpy(PCL-PtBA)2 and bpy(PLA-PtBA)2 macroligands, only bis(bpy) materials resulted. Thermal properties of macroligands and iron(II)-centered polymers were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). These synthetic studies lay the foundation for future investigations of how polymer composition and film morphology affect nanocluster formation in metal-centered star block copolymer templates.