Controlled hydrophobic\hydrophilic chitosan: colloidal phenomena and nanosphere formation

N-Phthaloylchitosan-grafted poly(ethylene glycol) methyl ether (mPEG) gives a milky solution when dispersed in water and a series of solvents. The appearance of turbidity depends on the types of solvents, i.e., protic and aprotic solvents. N-Phthaloylchitosangrafted mPEG shows an aggregation of sphere-like particles as observed by scanning electron microscopy. Transmission electron microscopy indicates that the spheres are at the nano level. When the chain length of mPEG is as high as 5×103 Da the sphere size becomes as small as 80–100 nm on average as observed by transmission electron microscopy. By simply adjusting the hydrophobicity\hydrophilicity of the chitosan chain, a stable nanosphere can be obtained directly