Ultrafast tailoring of carbon surfaces via electrochemically attached

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Ultrafast tailoring of carbon surfaces via electrochemically attached triazolinediones William Laure, Kevin De Bruycker, Pieter Espeel, David Fournier, Patrice Woisel, Filip E Du Prez, and Joël Lyskawa Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.7b03363 • Publication Date (Web): 22 Jan 2018 Downloaded from http://pubs.acs.org on January 22, 2018

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Ultrafast

tailoring

of

carbon

surfaces

via

electrochemically attached triazolinediones William Laure,1 Kevin De Bruycker,2 Pieter Espeel,2 David Fournier,1 Patrice Woisel,1 Filip E. Du Prez*2 and Joël Lyskawa*1 1

Université de Lille, CNRS, ENSCL, UMR 8207 - UMET - Unité Matériaux Et

Transformations, Ingénierie des Systèmes Polymères (ISP) team, F-59000 Lille, France 2

Polymer Chemistry Research Group, Centre of Macromolecular Chemistry (CMaC),

Department of Organic and Macromolecular Chemistry, Ghent University, Krijgslaan 281 S4, B-9000 Ghent, Belgium *Corresponding authors: [email protected], [email protected]

ABSTRACT The straightforward coupling between a triazolinedione (TAD) unit and citronellyl derivatives via an Alder-ene reaction has been exploited to tailor the physicochemical surface properties of glassy carbon surfaces (GC) in an ultrafast and additive-free manner. For this purpose, we first covalently grafted a TAD precursor onto GC via the electrochemical reduction of an in situ generated diazonium salt, which was then electrochemically oxidized into the desired GC-bonded TAD unit. A kinetic study of the modification of this reactive layer with an electroactive ferrocene probe proved that a complete functionalization was obtained in merely one minute. Further modification experiments with a fluorinated probe demonstrated that the surface properties can be swiftly tailored on demand. The different modification steps, as well as the efficiency of this strategy, were investigated by electrochemistry, contact angle goniometry and XPS analysis.

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INTRODUCTION Surface functionalization has attracted considerable interest the last decade, with the aim of designing surfaces with tailored physicochemical properties, such as wettability, corrosion resistance or adhesion, or to improve their biocompatibility and/or biological performances (e.g. cell affinity, tissues integration or prevention of biofilm formation). Consequently, several methods have been developed to modify surfaces, including plasma treatment,1 electrodeposition,2 layer-by-layer techniques3 and the immobilization of self-assembled monolayers.4 Alternatively, the covalent attachment of organic molecules or polymers using silane,5 phosphonic acid/ester6 or the bioinspired catechol chemistry,7 for example, was proven to be an efficient strategy to tailor the physicochemical surface properties,8 although the immobilization step remains highly time consuming. Finally, the electrochemical reduction of a diazonium salt represents a simple and powerful method to graft thin organic films onto conductive surfaces, allowing the covalent attachment of a wide range of functionalized aryl groups onto various surfaces including carbon, diamond, metals, metal oxides, alloys, semi-conductors, ceramics and polymers.9 While the aforementioned grafting techniques are versatile and widely applicable, the attachment of various target molecules also requires the synthesis of derivatives with surfacereactive moieties. Therefore, two-step modification procedures were developed, in which the substrate is first functionalized with a reactive moiety, followed by the immobilization of the target molecules or polymers, for example using the well-known copper-catalyzed azidealkyne cycloaddition (CuAAC)10 or reversible Diels-Alder cycloaddition.11 Nevertheless, despite the efficiency and ‘click’ character of such coupling reactions, they have a major drawback as they are time-consuming. Indeed, the slow kinetics of these processes can take from several hours to a few days, which limits the scope of possible applications.


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Consequently, decreasing the reaction time is of great interest to surface scientists for the development of novel functional materials, surfaces and nanoparticles. Triazolinedione (TAD) compounds12 were already demonstrated to have a quite high reactivity toward both conjugated dienes and isolated alkenes in Diels−Alder or Alder−ene reactions, respectively. Most often, these reactions are complete within seconds to minutes, proceed at room temperature in an equimolar way without the need for a catalyst, and thus meet the criteria of a click reaction. Consequently, triazolinediones were exploited to produce block copolymers,13 cross-linked plant-oil-based materials,14 and also covalently linked layerby-layer assemblies onto surfaces.15 Surprisingly, despite the attractive character of the TAD chemistry in the fast functionalization of materials, no example could be found in literature in which TAD was immobilized onto surfaces for the subsequent attachment of target molecules. In this context, we report on a facile and highly efficient strategy, using two subsequent electrochemical reactions, to obtain a TAD-functionalized substrate that can be further modified to tailor the surface properties in an ultrafast manner. First, an urazole moiety was covalently attached onto glassy carbon surfaces via the electrochemical reduction of an in situ generated diazonium salt. Subsequent electrochemical oxidation readily transformed the urazole into the desired triazolinedione. Finally, these TAD groups were modified with citronellyl-based probes via the ultrafast Alder-ene click reaction. Indeed, these citronellyl residues originate from citronellal, a readily available, naturally occurring terpene showing a high reactivity towards triazolinediones12. While a ferrocene probe was used to investigate the kinetics of the modification procedure, a fluorinated probe was applied to tailor the surface properties. The different steps of the modification, as well as the efficiency of the overall strategy, were investigated by electrochemistry, contact angle goniometry and XPS analysis.


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EXPERIMENTAL SECTION Materials All reagents were provided by Sigma-Aldrich and used as received unless otherwise noted. 4(4-aminophenyl)urazole 1 was synthesized according to literature.16 In situ electrochemical reduction of the diazonium salt In situ production and subsequent electrochemical reduction of the diazonium salt from 4-(4aminophenyl)urazole (1) was carried out in a 5mM acidic solution (0.5 M HCl) of 1 containing 1 equiv of sodium nitrite. The mixture was deaerated by bubbling an inert gas through the solution. Alder-ene click coupling on GC-surfaces Functionalization of TAD modified electrodes was achieved by dipping the GC surfaces into a 1mM solution of 2 or 3 in acetonitrile for 5 minutes at room temperature. The surfaces were then thoroughly rinsed with acetonitrile and dried with nitrogen flow. Analytical Techniques Electrochemical experiments (cyclic voltammetry) Electrochemical experiments were performed using an Autolab PGSTAT 30 workstation. The experiments were carried out in dry acetonitrile containing 0.1 M of recrystallized tetrabutylammonium hexafluorophosphate (TBAPF6) as electrolyte or in a phosphate buffer solution adjusted to pH=7. A three-electrode configuration was used with a glassy carbon (3 mm diameter) working electrode and a platinum rod as counter electrode. An Ag/AgCl electrode was used as reference. All solutions were purged with nitrogen prior to recording the electrochemical measurements. X-ray Photoelectron Spectroscopy (XPS) XPS analyses were performed on a Kratos Axis Ultra DLD system (Kratos Analytical) using a non-monochromatic Al Kα X-ray source (hυ = 1486.6 eV). The emission voltage and the


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current of this source were set to 12 kV and 3 mA respectively. The pressure in the analyzing chamber was maintained at 5.10-9 mbar or lower during analysis. Survey (0-1320 eV) and high resolution (C 1s) spectra were recorded at pass energies of 160 eV and 40 eV respectively. XPS analyses were performed with a takeoff angle of 90° relative to the sample surface. The core level spectra were referenced with the Ti 2p binding energy at 458.6 eV. Data treatment and peak fitting procedures were performed using Casa XPS software. Analyses were performed on glassy carbon surfaces with a diameter of 1.5 cm from HTW (Germany). Contact angle measurements Contact angles were evaluated with a Digidrop contact angle meter from GBX Scientific Instruments at room temperature. A water drop was used to measure the contact angle value (θ°). The measurement was repeated ten times to obtain an average value for the surface. Analyses were performed on glassy carbon surfaces with a diameter of 1.5 cm from HTW (Germany). Synthesis Citronellyl-modified Ferrocene 2 A solution of dicyclohexylcarbodiimide (DCC, 2.476g, 12 mmol) in dry DCM (15 mL) was added dropwise to an ice-cooled mixture of ferrocene carboxylic acid (2.3 g, 10 mmol), citronellol (2.74 mL, 15 mmol) and DMAP (122 mg, 1 mmol) in dry DCM (25 mL). The brown, turbid reaction mixture was stirred over the weekend at room temperature. After filtration, the solvent was evaporated and the crude product was purified by column chromatography (SiO2-hexane/EtOAc 100/0 to 95/5). The compound was then isolated as a brown oil in 65 % yield.


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1

H NMR (300 MHz, CDCl3), δ (ppm from TMS). 0.99 (d, 3H, CH3-CH), 1.26 (m, 1H, CH-

CH3), 1.37-1.84 (m, 2H, CH-CH2-CH2 and m, 2H, CH2-CH2-O), 1.62 (s, 3H, CH3-C(CH)CH3), 1.70 (s, 3H, CH3-C(CH)-CH3), 2.03 (m, 2H, C(CH)-CH2), 4.19 (s, 5H, CFcH), 4.25 (t, 2H, CH2-O-CO), 4.38 (t, 2H, CFcH-(CFcH)2-CFcH), 4.80 (t, 2H, CFcH-CFc-CFcH), 5.13 (m, 1H, CH3-C(CH)-CH3). 13

C NMR (300 MHz, CDCl3), δ (ppm from TMS). 17.7 (CH3-C(CH)-CH3), 19.5 (CH3-CH),

25.5 (C(CH)-CH2), 25.7 (CH3-C(CH)-CH3), 29.7 (CH-CH3), 35.8 (CH2-CH2-O), 37.1 (CHCH2-CH2), 62.7 (CH2-O), 69.7 (CFc-H), 70.1 (CFcH-CFc-CFcH), 71.2 (CFcH-(CFcH)2CFcH), 71.6 (CFc(IV)), 124.6 (C=CH), 131.4 (C=CH), 171.8 (C=O). Citronellyl-modified Zonyl 3 A suspension of N-hydroxysuccinimide (NHS, 4.06 g, 35.3 mmol) in dry dichloromethane was added dropwise to a solution (DCM, 200 mL) containing citronellic acid (4 g, 23.5 mmol) and DCC (7.27 g, 35.3 mmol) at -5°C under nitrogen. The reaction was allowed to return to room temperature and was stirred overnight. After filtration, the organic phase was washed three times with water (H2O, 3 x 100 mL) and dried over MgSO4. After filtration, the solvent was evaporated and the crude product was purified by column chromatography (SiO2DCM). The product was obtained in 62 % yield. 1

H NMR (300 MHz, CDCl3), δ (ppm from TMS). 1.06 (d, 3H, CH3-CH), 1.28-1.52 (m, 2H,

CH2-CH(CH3)), 1.61 (s, 3H, CH3-C(CH)-CH3), 1.68 (s, 3H, CH3-C(CH)-CH3), 1.95-2.14 (m, 3H, C(CH)-CH2 and CH-CH3), 2.4 and 2.62 (dd, 2H, CH2-CO-O), 2.83 (s, 4H, CO-CH2-CH2CO), 5.09 (m, 1H, CH3-C(CH)-CH3). 13

C NMR (300 MHz, CDCl3), δ (ppm from TMS). 17.7 (CH3-C(CH)), 19.4 (CH3-CH), 25.3

(C(CH)-CH2), 25.6 (CO-CH2-CH2-CO), 25.7 (CH3-C(CH)), 30.2 (CH3-CH), 36.5 (CH2CH(CH3)), 38.2 (CH2-CO-O), 123.9 (C(CH)-CH2), 131.9 (C(CH)-CH2), 168.0 (CH2-CO-O), 169.1 (CO-CH2-CH2-CO).


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A solution of the NHS functionalized compound (0.26 mg, 0.95 mmol) in anhydrous DCM (80 mL) was added dropwise to a solution containing amino Zonyl derivative11b (0.70 g, 0.87 mmol) and NEt3 (0.13 g, 1.3 mmol) in dry DCM (20 mL). The mixture was stirred at room temperature overnight. The organic phase was washed with NaOH 1M (3 x 100 mL), water (3 x 100 mL) and dried over MgSO4. After filtration, the solvent was removed under reduced pressure and the product was obtained as a brown viscous oil in 44 % yield. 1

H NMR (300 MHz, CDCl3), δ (ppm from TMS). 0.93 (d, 3H, CH3-CH), 1.10-1.44 (m, 2H,

CH2-CH(CH3)), 1.60 (s, 3H, CH3-C(CH)-CH3), 1.68 (s, 3H, CH3-C(CH)-CH3), 1.88-2.07 (m, 3H, C(CH)-CH2 and CH-CH3), 2.32-2.60 (m, 4H, CH2-CO-NH and CH2-CF2), 3.46 (t, 2H, CH2-NH-CO), 3.55 (t, 2H, CH2-CH2-NH-CO), 3.58-3.74 (m, 26H, CH2-CH2-O), 3.78 (t, CH2CH2-CF2), 5.09 (m, 1H, CH3-C(CH)-CH3). RESULTS AND DISCUSSION The triazolinedione (TAD) reactive moiety was immobilized in two steps onto a glassy carbon surface via the electrochemical reduction of a diazonium salt (Scheme 1).17 Considering the high reactivity of the TAD unit and to prevent side-reactions, we employed the 4-(4aminophenyl)urazole 1, i.e. a TAD-precursor, for the grafting.16

Scheme 1: Electrochemical deposition of the urazole derivative 1 and its subsequent oxidation into TAD allowing the ultrafast tailoring of carbon surfaces via Alder-ene reactions.

Urazole grafting


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The direct immobilization of urazole 1 onto glassy carbon surface was achieved in one step through the electrochemical reduction of the corresponding diazonium salt, which is generated in situ from an aqueous 1mM HCl (0.5M) solution of 1 upon addition of 1 eq. of sodium nitrite in the electrochemical cell.18

Figure 1: a) CV of GC electrode monitored after addition of 1 equiv of NaNO2 in the cell containing 1, first and subsequent scans. (Conditions: 5 mM of 1 in 0.5 M HCl, scan rate=100 mV/s vs Ag/AgCl) b) CV of the GC electrode modified by diazonium salt of 1 compared to the CV of phenyl urazole in solution (conditions: phosphate buffer at pH=3 and scan rates = 100 mV/s vs Ag/AgCl).

The corresponding cyclic voltammogram exhibits the characteristic broad peak that corresponds to the irreversible reduction of the diazonium salt and is assigned to the formation of the aryl radical, which then attaches to the GC surface (Figure 1Figure 1a). In

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addition, the following cyclic voltammetry deposition cycles show no further reduction peaks,

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while a decrease in current was observed, which results from the passivation of the GC electrode due to the formation of the grafted layer.19 The grafting of the urazole group onto the GC surface was first investigated by monitoring the CV of the urazole-functionalized electrode in a phosphate buffer at pH equal to 3 (Figure 1Figure 1b). The corresponding CV

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exhibits an anodic peak at 0.63V vs Ag/AgCl, attributed to the quasi-reversible oxidation of

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the urazole moiety, which is similar to the redox behavior of the phenylurazole in the same conditions. The grafting was further confirmed by X-ray photoelectron spectroscopy (XPS). Figure 2Figure 2b shows the survey spectra and atomic quantifications of GC electrodes


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before and after modification. After electrochemical grafting, the contribution of carbon at 285.0 eV decreased whereas those of nitrogen at 401.2 eV and oxygen at 532.4 eV increased significantly, as expected from the structure of the immobilized urazole moiety.

Figure 2: a) CV of GC electrode during the oxidation of the urazole into TAD, first and subsequent scan (conditions: acetonitrile TBAPF6 0.1M, v=100 mV/s) b) XPS spectrum of GC electrode before (lower) and after functionalization with urazole (middle) and finally after subsequent electro-oxidation and functionalization with fluorinated probe 3 (upper).

Generation of the triazolinedione reactive layer Urazoles are typically converted into triazolinediones with oxidants such as DABCObromine, N-bromosuccinimide or gaseous N2O4.12 However, because the TAD moieties in this work are surface-bound, we expected an inefficient oxidation, especially with the heterogeneous oxidants. Interestingly, Varmaghani et al. reported that a triazolinedione can also be generated in situ via the electrochemical oxidation of the corresponding urazole.20 While this strategy was solely used for the generation of sulfonamide derivatives, we explored this elegant oxidation procedure for the production of TAD-functional substrates. For this purpose, the urazole-functionalized electrode was subjected to ten oxidative cycles from 0.3 V to 1.7 V vs Ag/AgCl (t < 5 min). Acetonitrile was used as a solvent to prevent potential sidereactions of the generated TAD-unit in aqueous media. As depicted in Figure 2Figure 2a, the

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corresponding CVs clearly display the disappearance of the anodic and the cathodic waves



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assigned to the oxidation-reduction events of the urazole moiety, which proves the conversion of urazole into TAD.

Grafting of the electroactive ferrocene probe As a proof of concept, the reactive TAD-functionalized layer was subjected to an Alder-ene coupling reaction with the citronellyl-bearing electroactive ferrocene probe 2 (Scheme 1). The substituted double bond of the citronellyl group is an excellent reagent for Alder-ene reactions with TAD-substrates.12 The straightforward functionalization of the TAD layer was reached within 5 min at ambient temperature by simply dipping the electrode into a 1 mM solution of 2 in acetonitrile. It is worth noting that this reaction does not require any metal/ligand catalyst, additional photo-initiator or dye sensitizer. Moreover, no reaction occurs if a reference experiment is performed with the urazole-functionalized surface, thereby demonstrating the key role of the TAD-unit (see Figures S1 and S2). The main asset of this experiment lies in the fact that the reaction can be easily evaluated by electrochemical measurements (Figure

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3Figure 3a). As expected, the CV corresponding to the modified GC surface exhibits the


characteristic and well defined oxidation-reduction wave of the ferrocene probe at 0.7 V vs Ag/AgCl.11b Furthermore, the linear increase in current with scan rate (see Figure S3) on the one hand, and constant values of redox potentials vs scan rates on the other hand, further confirmed the covalent attachment of the ferrocene unit onto the GC electrode.


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Figure 3 a) Cyclic voltammogram of the GC surface after coupling reaction with the ferrocene probe 2 b) kinetic studies, evaluation of surface coverage as a function of reaction time (conditions: acetonitrile TBAPF6 0.1M, v=100mV/s).

The integration of the ferrocene signal (n = 1) reveals a surface coverage (Γ) of 1.05x1014 molecules/cm2, thereby indicating a high grafting density of the materials, as already stated for CuAAc21 or Diels-Alder reactions.11b Finally, the kinetics of the Alder-ene reaction were assessed by integrating the anodic peak of the ferrocene signal at different times to estimate the surface coverage. Figure 3Figure 3b demonstrates that the reaction is very fast, as the

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coupling was already complete in merely one minute. To the best of our knowledge, there is


no example in literature reporting a post-functionalization of surfaces in such an ultrafast, straightforward and efficient manner.22 Grafting of a fluorinated oligomer Finally, with the aim to modulate the physico-chemical surface properties of glassy carbon, Zonyl21 derivative 3 (Scheme 1) was synthesized, containing a perfluorinated alkyl chain, a short poly(ethylene glycol) block and a citronellyl residue. This partially fluorinated probe was subsequently immobilized onto TAD-functionalized GC surfaces by an Alder-ene click coupling, again within 1 min. The course of reaction was first studied via static water contact angle measurements. The unmodified GC surface exhibits a contact angle of 85°±1 in accordance with the presence of graphitic plains on the surface.23 After modification of the GC surface with the urazole (vide supra), the surface became more hydrophilic as the contact


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angle reached 72°±1, indicating that the grafting of the phenyl-urazole was effective. After oxidation into TAD and subsequent functionalization with 3, the contact angle of GC surfaces increased to 90°±2 in accordance with the immobilization of the hydrophobic oligomer onto the GC surfaces. This value is lower than previous studies dealing with the functionalization of titanium surfaces with Zonyl derivatives,11b, 21 which could be attributed to the difference of surface coverage between both surfaces, since titanium functionalization yielded a surface coverage that is one order of magnitude higher compared to GC surfaces. XPS measurements were carried out to confirm the successful grafting of the Zonyl derivative onto the GC surface. As depicted in Figure 2Figure 2b, the XPS survey spectrum of Zonyl-functionalized

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GC surfaces exhibits an intense peak at around 690 eV, attributed to the presence of fluorine


in the grafted film in accordance with the immobilization of 3 onto the GC surface.

Figure 4: XPS C1s core level spectra of TAD-grafted layer after click coupling reaction with fluorinated probe 3.


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In addition, deconvolution of the C1s core level spectrum of the layer resulting from click coupling with 3 (Figure 4) reveals, as expected, the presence of the N-C=O groups of the functionalized TAD layer at 289 eV and two additional components at 292 eV and 295 eV attributed respectively to the CF2 and CF3 groups of the Zonyl derivative24. These results corroborate the efficient grafting of the fluorinated probe onto GC surface through TAD chemistry in an ultrafast manner.

CONCLUSION In conclusion, we developed a facile strategy to obtain a TAD-functionalized glassy carbon surface by the electrochemical reduction of a urazole-bearing diazonium salt, which was generated in situ from the corresponding aniline, and its subsequent electrochemical oxidation into the reactive TAD moiety. The modification of the TAD-bearing surfaces via an ultrafast (< 1 min) and efficient Alder-ene click reaction with citronellyl derivatives was straightforward. Immobilization of a fluorinated oligomer, equipped with the TADcomplementary citronellyl residue, onto the TAD-GC surface allowed the on-demand, fast tuning of the physicochemical properties of the surface. According to its effectiveness, versatility and the ultrafast character of the functionalization, this strategy may facilitate the access to a myriad of smart surfaces with controlled interfacial properties, paving the way for promising applications in electronics, sensors, bio- and nanotechnology. Forthcoming research will focus on the reversible functionalization of TAD-surfaces by using reversibly reacting indole derivatives25 rather than the irreversibly reacting citronellyl derivatives, thereby allowing the design of smart surfaces with switchable properties in an ultrafast fashion.


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ACKNOWLEDGMENTS J.L. and D.F. thank ComUE Lille Nord de France and the Agence Nationale de la Recherche (DECIMAL - ANR-13-JS08-0011) for financial support. Chevreul Institute (FR 2638), Ministère de l’Enseignement Supérieur et de la Recherche, Région Hauts-de-France and FEDER are acknowledged for supporting this work. K.D.B. thanks the Research Foundation Flanders (FWO) for the funding of his PhD fellowship.

Supporting Information Available Experimental details and controlled experiment indicated in the manuscript are available free of charge via the Internet at http://pubs.acs.org. TOC

REFERENCES 1. Khelifa, F.; Ershov, S.; Habibi, Y.; Snyders, R.; Dubois, P., Free-Radical-Induced Grafting from Plasma Polymer Surfaces. Chem. Rev. 2016, 116 (6), 3975-4005. 2. Belanger, D.; Pinson, J., Electrografting: a powerful method for surface modification. Chem. Soc. Rev. 2011, 40 (7), 3995-4048. 3. Decher, G., Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites. Science 1997, 277 (5330), 1232-1237. 4. Love, J. C.; Estroff, L. A.; Kriebel, J. K.; Nuzzo, R. G.; Whitesides, G. M., Self-Assembled Monolayers of Thiolates on Metals as a Form of Nanotechnology. Chem. Rev. 2005, 105 (4), 11031170. 5. Li, C.; Benicewicz, B. C., Synthesis of Well-Defined Polymer Brushes Grafted onto Silica Nanoparticles via Surface Reversible Addition−Fragmenta>on Chain Transfer Polymeriza>on. Macromolecules 2005, 38 (14), 5929-5936.


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6. Zoulalian, V.; Zürcher, S.; Tosatti, S.; Textor, M.; Monge, S.; Robin, J.-J., Self-Assembly of Poly(ethylene glycol)−Poly(alkyl phosphonate) Terpolymers on Titanium Oxide Surfaces: Synthesis, Interface Characterization, Investigation of Nonfouling Properties, and Long-Term Stability. Langmuir 2010, 26 (1), 74-82. 7. Ye, Q.; Zhou, F.; Liu, W., Bioinspired catecholic chemistry for surface modification. Chemical Society Reviews 2011, 40 (7), 4244-4258. 8. Chen, W.-L.; Cordero, R.; Tran, H.; Ober, C. K., 50th Anniversary Perspective: Polymer Brushes: Novel Surfaces for Future Materials. Macromolecules 2017, 50 (11), 4089-4113. 9. Mohamed, A. A.; Salmi, Z.; Dahoumane, S. A.; Mekki, A.; Carbonnier, B.; Chehimi, M. M., Functionalization of nanomaterials with aryldiazonium salts. Adv. Colloid Interface Sci. 2015, 225, 1636. 10. (a) Leroux, Y. R.; Hapiot, P., Nanostructured Monolayers on Carbon Substrates Prepared by Electrografting of Protected Aryldiazonium Salts. Chem. Mater. 2013, 25 (3), 489-495; (b) Leroux, Y. R.; Hui, F.; Noël, J.-M.; Roux, C.; Downard, A. J.; Hapiot, P., Design of Robust Binary Film onto Carbon Surface Using Diazonium Electrochemistry. Langmuir 2011, 27 (17), 11222-11228; (c) Evrard, D.; Lambert, F.; Policar, C.; Balland, V.; Limoges, B., Electrochemical Functionalization of Carbon Surfaces by Aromatic Azide or Alkyne Molecules: A Versatile Platform for Click Chemistry. Chem. Eur. J. 2008, 14 (30), 9286-9291. 11. (a) Preuss, C. M.; Goldmann, A. S.; Trouillet, V.; Walther, A.; Barner-Kowollik, C., Biomimetic Dopamine-Diels–Alder Switches. Macromolecular Rapid Communications 2013, 34 (8), 640-644; (b) Laure, W.; Woisel, P.; Lyskawa, J., Switching the Wettability of Titanium Surfaces through Diels–Alder Chemistry. Chemistry of Materials 2014, 26 (12), 3771-3780. 12. De Bruycker, K.; Billiet, S.; Houck, H. A.; Chattopadhyay, S.; Winne, J. M.; Du Prez, F. E., Triazolinediones as Highly Enabling Synthetic Tools. Chem. Rev. 2016, 116 (6), 3919-3974. 13. Vandewalle, S.; Billiet, S.; Driessen, F.; Du Prez, F. E., Macromolecular Coupling in Seconds of Triazolinedione End-Functionalized Polymers Prepared by RAFT Polymerization. ACS Macro Letters 2016, 5 (6), 766-771. 14. Türünç, O.; Billiet, S.; De Bruycker, K.; Ouardad, S.; Winne, J.; Du Prez, F. E., From plant oils to plant foils: Straightforward functionalization and crosslinking of natural plant oils with triazolinediones. Eur. Polym. J. 2015, 65, 286-297. 15. Vonhören, B.; Roling, O.; De Bruycker, K.; Calvo, R.; Du Prez, F. E.; Ravoo, B. J., Ultrafast Layerby-Layer Assembly of Thin Organic Films Based on Triazolinedione Click Chemistry. ACS Macro Letters 2015, 4 (3), 331-334. 16. Billiet, S.; De Bruycker, K.; Driessen, F.; Goossens, H.; Van Speybroeck, V.; Winne, J. M.; Du Prez, F. E., Triazolinediones enable ultrafast and reversible click chemistry for the design of dynamic polymer systems. Nature Chem. 2014, 6 (9), 815-821. 17. Delamar, M.; Hitmi, R.; Pinson, J.; Saveant, J. M., Covalent modification of carbon surfaces by grafting of functionalized aryl radicals produced from electrochemical reduction of diazonium salts. J. Am. Chem. Soc. 1992, 114 (14), 5883-5884. 18. Baranton, S.; Bélanger, D., Electrochemical Derivatization of Carbon Surface by Reduction of in Situ Generated Diazonium Cations. J. Phys. Chem. B 2005, 109 (51), 24401-24410. 19. Allongue, P.; Delamar, M.; Desbat, B.; Fagebaume, O.; Hitmi, R.; Pinson, J.; Saveant, J.-M., Covalent Modification of Carbon Surfaces by Aryl Radicals Generated from the Electrochemical Reduction of Diazonium Salts. J. Am. Chem. Soc. 1997, 119 (1), 201-207. 20. Varmaghani, F.; Nematollahi, D.; Mallakpour, S.; Esmaili, R., Electrochemical oxidation of 4substituted urazoles in the presence of arylsulfinic acids: an efficient method for the synthesis of new sulfonamide derivatives. Green Chem. 2012, 14 (4), 963-967. 21. Watson, M. A.; Lyskawa, J.; Zobrist, C.; Fournier, D.; Jimenez, M.; Traisnel, M.; Gengembre, L.; Woisel, P., A “Clickable” Titanium Surface Platform. Langmuir 2010, 26 (20), 15920-15924. 22. Preuss, C. M.; Zieger, M. M.; Rodriguez-Emmenegger, C.; Zydziak, N.; Trouillet, V.; Goldmann, A. S.; Barner-Kowollik, C., Fusing Catechol-Driven Surface Anchoring with Rapid Hetero Diels–Alder Ligation. ACS Macro Letters 2014, 3 (11), 1169-1173.


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Ultrafast tailoring of carbon surfaces via electrochemically attached

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