Microphase separation and hydrophobicity of urethane/siloxane copolymers with low siloxane content

• Synthesis of urethane/siloxane copolymer with a phase separated structure.
• Phase separated structure depends on the conversion and casting temperature.
• Phase structure measured by AFM, tapping mode.
• Contact angle depends on rugosity and siloxane concentration.

Polyurethane–siloxane thermoset copolymers were obtained from Isophorone diisocyanate trimer, Polycaprolactone triol and 10% of hydroxy terminated Polydimethyl siloxane. The copolymers showed a phase separated structure that depended on the conversion of the reaction and casting temperature. The different samples obtained had water contact angles higher than 90°. Moreover the contact angle values presented a maximum at intermediate reaction conversion. Although FTIR measurements showed that siloxane concentration at the surface increased with reaction time, the maximum contact angle value was related to the higher roughness calculated from AFM images. DMTA results confirmed that the phase separation was higher at intermediate conversions.