Synthesis of molecular brushes with gradient in grafting density by atom transfer polymerization

Macromolecular brushes with a gradient of side-chain spacing along the backbone have been synthesized by the grafting from approach using atom transfer radical polymerization. A macroinitiator was prepared in two steps, first by conducting a gradient copolymerization of MMA and HEMA-TMS followed by transformation of the resulting poly(MMA-grad-HEMA-TMS) to poly(MMA-grad-BPEM). The gradient composition of the macroinitiator was a forced gradient formed by continuous feeding of HEMA-TMS during MMA polymerization. The gradient structure was characterized by monitoring monomer conversion (GC) and molecular weight evolution (GPC) during copolymerization. AFM measurements demonstrated the characteristic anisotropy of the molecular structure by resolving individual brush molecules with a bulky head and a thin tail.