PDMS‐Modified Polyurethane Films with Low Water Contact Angle Hysteresis

Abstract

AbstractSummary: Polyurethane (PU) films with low water contact angle hysteresis (CAH) were prepared by employing less than 0.2 wt.‐% of mono‐ or bihydroxyl‐functionalized polydimethylsiloxane (PDMS) of 60–70 DMS repeat units. A Si content of as low as 0.03 wt.‐% was sufficient to lead to a CAH of 20°. The curing temperature demonstrated strong effects on the wetting behavior of the PDMS‐modified PU films: a relatively low curing temperature (40 °C) resulted in stronger surface segregation of PDMS than higher curing temperatures, giving rise to high water receding CAs and thus low CAH. It was found from angle‐resolved X‐ray photoelectron spectroscopy analysis that the surface silicon content was greater when cured at a lower temperature. The surface of PDMS‐modified PU films was very smooth from AFM observations, but the Si content had strong effects on the surface phase contrast. The chain length of 60–70 DMS repeating units for both mono‐ and bifunctional PDMS appeared to be long enough to prevent the surface reorganization during the CA measurements.Schematic, simplified illustration of PDMS chains at the surface of PU films modified by PDMS60OH and PDMS70(OH)2.magnified imageSchematic, simplified illustration of PDMS chains at the surface of PU films modified by PDMS60OH and PDMS70(OH)2.