PROJECT TITLE :

Highly hydrophobic and partially conductive polydimethylsiloxane surface produced by direct fluorination and subsequent annealing

ABSTRACT:

Highly hydrophobic materials are of interest in several scientific and technological areas. To enhance surface properties of polydimethylsiloxane (PDMS), PDMS sheets were surface fluorinated in a laboratory vessel using a F2/N2 mixture with twelve.5p.c F2 by volume at regarding fifty five °C below 0.1 MPa for different times of fifteen, 30, and 60min. Surface wettability and surface energy were evaluated by contact angle measurements and surface energy calculations, and surface electrical properties were investigated by measurements of surface conductivity and surface potential decay. These results show that direct fluorination created a highly hydrophobic and partially conductive PDMS surface with low surface energy, that had little correlation with fluorination time in the investigated range of 15 to sixty min. Moreover, annealing of the surface fluorinated PDMS sheets at one hundred fifty °C for sixty min caused a additional increase in surface hydrophobicity, while reduced surface conduction of the fluorinated PDMS sheets. Attenuated total reflection infrared analyses and scanning electron microscope surface and cross-section observations reveal substantial changes in physicochemical characteristics of the sheet surface layers due to direct fluorination. The high hydrophobicity or low surface energy is attributed to the changes in chemical composition and structure of the surface layers and in their surface roughness. The partial conductivity of the fluorinated PDMS surfaces may be a results of the competition between the compositional modification and the structural change.