Novel Transparent Zirconium-Based
Hybrid Material
With Multilayered Nanostructures: Studies of Surface Dewettability
Toward Alkane Liquids
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Abstract
We have successfully prepared unique inorganic–organic
hybrid
materials that demonstrate excellent transparency and dewettability
toward various alkane liquids (<i>n</i>-hexadecane, <i>n</i>-dodecane and <i>n</i>-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<sub>3</sub>(CH<sub>2</sub>)<sub><i>x</i>−2</sub>COOH where <i>x</i> = 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<sub><i>x</i></sub>) 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<sub><i>x</i>≥18</sub>) spontaneously self-assembled
into lamella structures with <i>d</i>-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<sub><i>x</i><18</sub>) 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<i><sub>x</sub></i> 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<sub>14</sub> film surfaces without pinning at low tilt angles
(∼6°)