Abstract
Bis-alkynylated oligoethyleneglycol (OEG) and a monopropargyl-functionalized perfluorinated ethylene glycol (FEG) were
clicked to azide-functionalized gold surface (Au–N
3) at room temperature via the well known 1,3 cycloaddition
click chemical reaction. The Au–N
3 substrate was obtained by nucleophilic attack of NaN
3 on gold substrates modified by the electrochemical reduction of the
BF
4
-
,
+N
2–C
6H
4–CH
2Br diazonium salt. This electrochemical process yields aryl layer-modified gold of the type Au–C
6H
4–CH
2Br (hereafter Au–Br). The untreated and modified gold plates were examined by XPS, PMIRRAS and contact angle measurements. XPS brought evidence for electrografting aryl layers by the detection of Br3d; azide functionalization by the increase of the N/Br atomic ratio; and
click reaction of OEG with Au–N
3 by the increase of O/N ratio. In addition, the perfluorinated plate (Au-FEG) exhibited F1s and characteristic C1s peaks from -(CF
2)
7- chain and terminal CF
3. Infra red spectroscopy (PMIRRAS) evidenced (i) grafting N
3 to Au–Br; (ii) characteristic stretching bands, from ethylene glycol units, C–O–C (1100–1300
cm
−1); CF
2 (1000–1100
cm
−1) and CF
3 (1100–1350
cm
−1) from FEG grafts; and (iii) suppression of alkynyl bands from OEG and FEG after surface
click chemistry. More importantly, PMIRRAS results support an important bridging of the bispropargyl oligoethylene glycol at the gold surface. Water drop contact angles were found to be 48.7° and 83.0° for Au-OEG and Au-FEG, respectively, therefore highlighting the control over the hydrophilic/hydrophobic character of the
clicked substrate.
This work shows that
clicking macromolecules to grafted, diazonium salt-derived aryl layers is a novel, simple and valuable approach for designing robust, functional surface organic coatings.