Improving Superhydrophobicity of PDMS by Embedding Fluorinated POSS Cages*

Designing superhydrophobic surfaces is one of the value addition processes for biomedical polydimethylsiloxanes (PDMS) devices, which can be obtained by increasing nanoscale surface roughness and introducing low surface energy molecules. Current work explores simple fabrication methods that enhance the hydrophobicity of PDMS while retaining the durability. Two species of polyhedral oligomeric silsesquioxanes with short fluorocarbon tethers (FPOSS) were incorporated into PDMS using four methods. These methods were non-solvent blending, solvent blending, spraying FPOSS/PDMS solution onto partially cured PDMS and spraying only FPOSS solution onto partially cured PDMS surfaces. Among them, spraying FPOSS onto partially cured PDMS served the highest hydrophobicity with water contact angle of 167°. Trifluoropropylisobutyl POSS always consisted of higher hydrophobicity rather than trifluoropropyl POSS. Hence, the compatibility of functional groups attached to FPOSS has played a major role other than increasing the fluorine composition. Amorphous nature of the PDMS was improved upon incorporating FPOSS and it was method dependent. Hydrophobicity and durability of the spray coated PDMS-FPOSS blends confirms the possibility of using those in biomedical devises.