AFM investigation of effect of absorbed water layer structure on growth mechanism of octadecyltrichlorosilane self-assembled monolayer on oxidized silicon

Surface Modification of a Polyester-Augmented Cellulose Filter for Dehydration of Low-Sulfur Diesel

Fuel filters play an essential role in protecting the injection equipment and fuel tanks against corrosion and damage of diesel engines. Diesel fuel separators are typically made of treated cellulose, fiberglass, or mixed fibrous media (composites), modified with various chemicals to obtain a hydrophobic surface. In the presented research, a modification procedure of polyester fibers supported on cellulose using octadecyltrichlorosilane (OTS) has been developed. The OTS coating renders the filter media superhydrophobic with water contact angle and roll-off angle of 156.4 and 4.9°, respectively. The performance of the modified material was verified in dispersed water removal from low-sulfur diesel fuel. High efficiency and a reliable operation in test conditions were confirmed.

Dependence of deposition method on the molecular structure and stability of organosilanes revealed from degrafting by tetrabutylammonium fluoride

We probe the structure of self-assembled monolayers (SAMs) comprising organosilanes deposited on flat silica-based surfaces prepared by liquid and vapor deposition by removing the organosilane molecules gradually from the underlying substrate via tetrabutylammonium fluoride (TBAF). Removal of organosilanes from the surface involves the cleavage of all pertinent Si-O bonds that anchor the organosilane molecules to the SAM, i.e., direct organosilane-surface linkages and in-plane crosslinks between neighboring organosilanes. We gain insight into the organosilane structure and stability by monitoring the organosilane density as a function of exposure time to TBAF. Degrafting of trifunctional chloro- and methoxy-alkylsilanes deposited from solution yields similar degrafting kinetics. We observe fast degrafting for organosilane SAMs deposited from the vapor phase, indicating that SAMs prepared in this manner form more loosely packed arrays, with less in-plane connectivity, compared to their solution-deposited counterparts. Bulkier, fluorinated silanes form more stable SAMs due to their ability to readily align and form a network with few aggregates and a relatively high fraction of surface bonds. The addition of a polymer brush to an anchored organosilane molecule demonstrates that increased bond tension accelerates the degrafting process despite the increased diffusion resistance.