Successful therapy of cancer has been seriously hindered by the insolubility and instability of antitumor drugs,and more critically,by the nonspecific delivery and poor penetration of drug formulation into tumor site.1 Therefore,it is immediately clear that a safe and effective treatment needs to be explored to deliver these agents to the site of action precisely and timely.Recently,drug delivery systems(DDS)have shown great potential for cancer therapy,owing to their unique micellization behavior and improved property as drug carriers.To overcome various physiological barriers in vivo,DDS are expected to be equipped with multiple functions.2 Polyurethanes have emerged as one of the most promising platforms for drug delivery due to their special modular structures which can integrate multiple functions in an individual molecular chain.