Facile,Versatile Prepolymerization and Postpolymerization Functionalization Approaches for Well-Defined Fluorescent Conjugated Fluorene-Based Glycopolymers

摘要

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-dimethy-oxyphenylene-ethynylene) 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(PPh_3)_2Cl_2 and 10% PPh_3.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.