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Hydrophilicity describes affinity for water. Regions with chemical polarity or electric charge can interact favorably with water, including through hydrogen bonds where suitable groups are present. Hydrophilic regions of membrane-forming phospholipids face the water on either side of a lipid bilayer. Such affinity does not mean forming covalent bonds with every neighboring substance, nor does it require a net negative electric charge. See Alberts et al.: the chemical components of a cell.

Science240, pp.62–63. The abstract describes sulfur-bound hydroxyl-terminated monolayers and the effect of mixed chain lengths on order and hydrophilicity. It provides a direct experimental example for surface-chemistry control.