Controlled grafting of a well-defined glycopolymer on a solid surface by surface-initiated atom transfer radical polymerization

The atom transfer radical polymerization (ATRP) technique using the copper (Cu)/4,4'-di-n-heptyl-2,2'-bipyridine (dHbipy) complexes was applied to the graft polymerization of a sugar-carrying methacrylate, 3-O-methacryloyl-1,2:5,6-di-0-isopropylidene-D-glucofuranose (MAIpGlc), on the substrate on which the monolayer of the initiator, 2-(4-chlorosulfonylphenyl)ethyltrimethoxsilane was immobilized by the Langmuir-Blodgett technique. Ellipsometric and atomic force microscopic analyses confirmed that the polymerization carried out in the presence of the (sacrificing) free initiator, p-toluenesulfonyl chloride, afforded a homogeneous graft layer on the substrate. The thickness d of the graft layer in a dry state increased with reaction time and in proportion to the number-average molecular weight M-n of the (low-polydispersity) free polymers produced in the solution. This proportional relationship between d and M-n strongly suggests a controlled growth of the graft chains, as well as of the free chains, with the graft density kept constant. Grazing-angle reflection-absorption FTIR studies revealed that the isopropylidenyl groups of the poly(MAIpGlc) grafts were quantitatively converted to the hydroxyl groups by treatment with formic acid, thus producing the first solid surface densely grafted with a well-defined glucose-carrying polymer.