Our working concept is to graft CS with watersolublepoly (butylene tartrate) (PBT), which has two pendant hydroxyl groups on every repeating unit, to improve the solubility of CS in water by a green process. It has been reported that aliphatic polyester with hydrophilic pendant hydroxyl groups can be useful in controlled drug delivery systems [11–13]. However, sincependant hydroxyl groups can take part in the polycondensationreaction resulting in branched and crosslinked structure, it isdifficult to synthesize linear PBT. Therefore, the synthesis process always involves tedious protection and deprotection of the