A hydrophobic self-assembled monolayer with improved adhesion to aluminum for deicing application

A previously developed laser-generated stress wave procedure for measuring the tensile strength of ice/solid interfaces was used to study the effectiveness of a self-assembled monolayer of dimethyl-n-octadecilcholorsilane (DMOCS) in providing a hydrophobic surface to a 6061 At alloy. In this experiment, a laser-induced compressive stress wave travels through a substrate disc that has a layer of ice grown on its front surface. The compressive stress pulse reflects into a tensile wave from the free surface of ice and pulls the ice/Al interface apart at a sufficiently high amplitude. The interface strength was calculated using a wave mechanics simulation, with the interferometrically recorded free surface velocity of a bare At substrate (measured under identical ice spallation conditions) as an input, The tensile strength of the ice/DMOCS interface at -10 degreesC was found to be 131 MPa, which is the lowest among all surfaces tested to date, which include, as-received Al surfaces (274 MPa), surfaces prepared with chemical and mechanical polishing (181 MPa), and PMMA-coated (190 MPa) and polyimide-coated (177 MPa) At surfaces. The two methyl groups attached to the outer end of the carbon chain in the DMOCS coating provide a completely hydrophobic surface, while its silane group at the bottom most end reacts with the adsorbed hydroxyl groups on the aluminum surface to form a strong Si to At covalent bond. Thus, DMOCS coatings present an appealing alternative to various presently available ice mitigating surface strategies, by providing a longer-lasting surface with the highest hydrophobicity possible. (C) 2001 Elsevier Science Ltd. All rights reserved.