A methodology is described for introducing a thin layer of covalently attached benzaldehyde on glassy carbon surfaces using aryl diazonium chemistry. Usually the electroreduction of aryl diazonium salts leads to the formation of an ill-defined multilayer because of the involvement of highly reactive aryl radicals that can add to already-grafted aryl groups. However, in this study we used a two-step "formation-degradation" procedure to solve this problem with the first step consisting of an electrografting of an aryl diazonium salt of a long-chain and bulky alkyl hydrazone onto a glassy carbon surface. The design of the hydrazone group serves to minimize multilayer formation by greatly diminishing the grafting rate after the first-layer formation and at the same time preventing radical additions from taking place at the inner aryl ring. Another valuable property of the hydrazone group is that it easily can be deprotected to the corresponding aldehyde by acid hydrolysis (i.e., the degradation step). In this manner, a thin and well-defined film of covalently attached benzaldehyde with an estimated coverage of 4 x 10(-10) mol cm(-2) was formed. The electrochemical responses of benzaldehyde were highly reproducible and largely independent of grafting medium (water or DMSO) and along with that also the thickness of the initially grafted film. AFM and contact angle measurements support the findings. The "formation-degradation" approach thus lays the foundation for carrying out further functionalization reactions in a controlled manner.

Immobilization of submonolayers to 4-5 multilayers of organic molecules on carbon surfaces can be performed by in situ generation of aryl radicals from aryltriazenes. The central idea consists of oxidatively forming an electrogenerated acid of N,N'-diphenylhydrazine to convert the aryltriazene to the corresponding diazonium salt in the diffusion layer of the electrode. In a second step, the diazonium salt is reduced at the same electrode to give a surface of covalently attached aryl groups. In this manner, various moieties tethered to the aryl groups can be immobilized on the surface. Here a ferrocenyl group was introduced as redox marker, the electrochemical signal of which is extraordinarily well-defined. This behavior is independent of film thickness, the latter being easily controlled by the number of repetitive cycles performed. It is also demonstrated that the new approach is suitable for patterning of surfaces using scanning electrochemical microscopy.

An electrochemical approach is presented for carrying out controlled modification of carbon and metal surfaces with aryl groups through mild anodic oxidation of arylhydrazines. Electrochemical, PM-IRRAS, and ellipsometrical measurements reveal that monolayers are formed, the thickness of which is essentially independent of the substituent, pH, and grafting time and potential. This feature makes the approach very tolerant toward variations in the experimental conditions. Hence, this method should be considered as a strong option if the aim is to form thin, well-defined, and covalently assembled aryl layers on surfaces.

In this work, various lengths and densities of poly(methyl methacrylate) (PMMA) brushes were synthesized on stainless steel (SS) surfaces via surface initiated atom transfer radical polymerization. Subsequently, the joints between the bulk PMMA and the PMMA brushed stainless steel were obtained by injection molding, and for these the degree of adhesion was assessed by tensile testing. Several conditions are required to facilitate the mixing between the brushes and the bulk polymer and to reduce the residual stress at the interface: preheating of the SS samples before the injection molding; a long packing time; and a mold temperature above the glass transition temperature (Tg) of PMMA during the injection molding. This treatment leads to a cohesive failure in the bulk PMMA. It was observed that the stress concentrated at the rim, due to contraction of bulk PMMA during cooling, results in a weak adhesion at the rim of the joint. A combination of high density and long brush length of PMMA film provides better adhesion. The large number of PMMA brush chains apparently promotes good penetration into the bulk PMMA chains and ultimately results in high adhesion strength.

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