The feasibility of employing Diels-Alder reaction for improving the grafting efficiency and controllability of poly(ethylene glycol) (PEG) towards chitosan (CS) was evaluated.Diene-capped PEG (PEG-diene) was conveniently obtained through thio-acrylate reaction between furfuryl mercaptan and poly-(ethylene glycol) methyl ether methacrylate (PEGMEMA).By using sodium dodecyl sulphate-chitosan complex (SCC) as an organo-soluble precursor

the dienophile

(N-(2-carboxyethyl)maleimide)

was regioselectively conjugated to the hydroxy groups of chitosan backbone through conventional coupling method.Sodium dodecyl sulphate (SDS) was then removed from the conjugate simply by precipitating the reaction solution into tris(hydroxymethyl)aminomethane(Tris) solution to give the chitosan intermediate carrying dienophile moieties (CS-dienophile).In situ 1H-NMR was further used for studying the Diels-Alder reactions between CS-dienophile and PEG-diene.It was found that PEG could be grafted onto chitosan backbone in aqueous media under mild conditions.In addition

the PEG grafts could be detached from the graft copolymers at high temperature through retro Diels-Alder reaction.