Reversible addition fragmentation chain transfer (RAFT) has been used to synthesize polymer brushes. Styrene, methyl methacrylate, and N,N-dimethylacrylamide brushes were prepared under RAFT conditions using silicate surfaces that were modified with surface-immobilized azo initiators. Films with controlled thicknesses were produced. RAFT was also used to synthesize PS-b-PDMA and PDMA-b-PMMA block copolymer brushes that displayed reversible surface properties upon treatment with block-selective solvents.
The polymerization of N,N-dimethylacrylamide (DMA) under atom transfer radical polymerization (ATRP) conditions was studied. The ligand, solvent (water, n-butanol, and toluene), initiator,
and Cu halide were varied. High monomer conversions were obtained using the Me4Cyclam ligand.
Polymerizations in water that were initiated at room temperature were complete within minutes. However,
none of the experimental conditions produced a controlled polymerization. This conclusion is based on
broad molecular weight distributions, poor agreement between theoretical and experimental M
n,
incremental monomer addition experiments, and end group analysis. We believe that the Cu salts complex
to the amide group of the chain ends and stabilize the radical. This stabilization retards the deactivation
step in ATRP and produces an unacceptably high concentration of radicals which leads to spontaneous
termination reactions. In addition, we have indirect evidence for a cyclization reaction involving
nucleophilic Br displacement by the penultimate amide nitrogen; this cyclic onium intermediate undergoes
hydrolysis to form a hydroxy-terminated polymer.
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