Amino-terminated polydimethylsiloane (SN2) was synthesized by using hydroxyl-terminated polydimethylsiloxane (PDMS) and aminopropyl siloxane coupling agent (DB-912).And the silicone-polyurethane (Si-PU) block copolymer was synthesized by using SN2 as a chain extender and polyurethane prepolymer.The effects of the SN2 and prepolymer of polyurethane feed ratio on the rheological behavior of the copolymer solution in isopropanol (IPA) and the properties of its film were studied in detail.It was found that the Si-PU block copolymer IPA solution with a concentration of 25 wt% exhibited low apparent viscosity and the characteristics of Newtonian fluid within the measuring shear rate scope.During film casting

the SN2 blocks may migrate toward the surface

which led to a surface contact angle to water over 110.With the increasing of SN2 block content

the surface contact angles of films to water increased slightly.When the films were soaked in the water for 24 h

the water absorptions were very low

and the water-repellence was pretty good.The copolymer film showed water absorption lower than 1.5 wt%.With the increasing of SN2 block content

the water absorptions were very low and did not change a lot.However

if the content of SN2 block was too high

the water absorption of films increased obviously owing to the increase of hydrophilic groups (NH2) which possessed good attraction for water molecules.