AbstractTo create new biofunctional materials, a polycaprolactone‐polysiloxane‐polycaprolactone (PCL‐PMVS‐PCL) carrying lactose was developed by ring‐opening polymerization and esterification reaction. 1H NMR and Fourier transform IR spectroscopy confirmed synthesis of the product. Gel permeation chromatography and DSC were used to evaluate its molecular structure. With propagation of the PCL molecular chain, the copolymer transforms from the amorphous form to crystalline, and its solubility in chloroform is modified. Change of the lactose grafting ratio brings about little influence on the solubility of the grafted copolymer. The product exhibits good film‐forming ability after chain extension. The results suggest that the grafted copolymer not only can form composites with commercial biodegradable polyester but also can be processed alone to serve for biomedical engineering. © 2018 Society of Chemical Industry