A Method for the Preparation of Hydrophilic/Hydrophobic Patterned Surfaces by Using Photoinitiated Hydrosilylation

Recently there has been considerable interest in hydrophilic/hydrophobic patterned surfaces because they serve as important templates for selective deposition of various materials. We report a novel and simple method for the creation of hydrophilic/hydrophobic patterned surfaces using soft UV irradiation (365 nm wavelength). The method employed a photoinitiated hydrosilylation reaction of vinyl terminated polydimethylsiloxane with H-Si groups catalyzed by platinum(II) acetylacetonate. In UV-irradiated regions, the photo hydrosilylation reaction occurred to form hydrophobic regions. In unirradiated regions, the remaining H-Si groups were converted to HO-Si groups in the presence of aqueous sodium hydroxide to form hydrophilic regions. The photoinitiated hydrosilylation reaction completed within a little over 1 min, which was confirmed by water contact angle measurements and reflection-absorption spectroscopy. The value of the water contact angle for the hydrophilic regions was about 10deg and that for the hydrophobic regions was about 103deg. The success of pattern formation at the micron scale was confirmed by scanning electron microscope.