Facile, versatile prepolymerization and postpolymerization functionalization approaches for well-defined fluorescent conjugated fluorene-based glycopolymers

We have developed facile, versatile prepolymerization and postpolymerization functionalization approaches to prepare well-defined fluorescent conjugated fluorene-based glycopolymers ( polymers A and B) through thioether formation. Well-defined glucose-carrying monomer ( 5) and conjugated polymer ( polymer 2) were prepared by coupling the key precursors, 2,7-diiodo-9,9-bis(6'-bromohexyl) fluorene ( 2) and poly[(9,9-bis( 6'-bromohexyl)-2,7-fluorenylene)-alt-1,4-phenylene] (polymer 1) with an excess of 1-thio-beta-D-glucose tetraacetate ( 3) in a basic condition, respectively. A well-defined poly(2,7-fluorenylene-ethynylene)-alt-1,4-(2,5-dimethyoxyphenyleneethynylene) bearing peracetylated glucose residues ( polymer 3) was prepared by a palladium catalyzed Sonogashira coupling polymerization of monomer 5 with a diethynylbenzene in the presence of 5% CuI, 5% Pd(PPh3)(2)Cl-2 and 10% PPh3. Polymers 2 and 3 were deacetylated under Zemplen conditions in methanol and methylene chloride containing sodium methoxide, affording two fluorene-based conjugated glycopolymers A and B, respectively. Polymer A was also obtained by the reaction of polymer 1 with 1-thio-beta-D-glucose sodium salt hydrate ( 4) in a basic condition. The composition and purity of the products were reliably analyzed by 1H NMR. Water-soluble fluorene-based conjugated copolymer bearing glucose pendants with tri(ethylene glycol) tethers ( polymer C) was prepared by the postpolymerization functionalization approach. This thioether formation reaction offers a very effective conjugation method to covalently attach protected or unprotected carbohydrate residues to fluorescent conjugated polymers.