Novel transparent zirconium-based hybrid material with multilayered nanostructures: studies of surface dewettability toward alkane liquids.

We have successfully prepared unique inorganic-organic hybrid materials that demonstrate excellent transparency and dewettability toward various alkane liquids (n-hexadecane, n-dodecane and n-decane) without relying on conventional surface roughening and perfluorination. Such coatings were made using a novel family of hybrid materials generated by substituting carboxylic acids, with a range of alkyl chain lengths (CH(3)(CH(2))(x-2)COOH where x = total carbon number, i.e., 10, 12, 14, 16, 18, 22, or 24, into zirconium (Zr) tetra-propoxide complexes. This precursor was then mixed with acetic acid and spincast to produce transparent thin Zr-carboxylic acid (ZrCA(x)) hybrid films using a nonhydrolytic sol-gel process. Fourier transform infrared spectroscopy provided proof of Zr-O-Zr network formation in the films upon casting and also followed changes to the physical nature (liquid-like or solid-like) of the alkyl chain assemblies depending upon alkyl chain length. X-ray diffractometry revealed that the hybrid films prepared using the longer chain carboxylic acids (ZrCA(x≥18)) spontaneously self-assembled into lamella structures with d-spacings ranging from 29.5 to 32.7 Angstroms, depending on the length of the alkyl chain. On the other hand the remaining films (ZrCA(x<18)) showed no such ordering. Moreover, the dynamic dewetting behavior of our hybrid films with alkane liquids was also strongly affected by alkyl chain length. ZrCA(x) films with x = 12, 14, and 16 showed the best dynamic oleophobicity among the seven hybrid films. In particular, small volume alkane droplets (5 μL) could be easily set in motion to move across and off ZrCA(14) film surfaces without pinning at low tilt angles (~6°).