Electrochemical Methods for Preparing Polymer-Immobilized Nanoparticles

Electrochemical Methods for Preparing Polymer-Immobilized Nanoparticles 

The electrochemical and electroflotation methods are widely used to prepare of chemisorbed macromolecules bound to colloidal metal particles generated in situ. Electrochemical polymerization reactions are heterogeneous They are initiated on the electrode surface, while other stages (chain growth or termination) occm, as a rule, in the liquid phase. The yield of a polymer depends on the chemical and physical nature of the electrodes and their surface, electrode overvoltage, potential rmder which the reaction occurs, and electrical current density. The nature of the electrode material (metals or alloys, thin metallic coats, etc.) determines the characteristics of electron-transfer initiation and polymerization. Direct electron transfer between the electrode and monomer, cathodic deposition, and anodic solubilization of metals are optimum for electrochemical polymerization. Metal salts are the precursors of nanoparticles, which may act as specific electrochemical activators. Nanoparticles can influence activations through direct chemical binding to the monomer and by virtue of transfer, decomposition, or catalytic effects. Nonetheless, electrochemical polymerization has found only limited use in the preparation of polymer-immobilized nanoparticles. 

The preparation of metal organosols by electrolysis in a two-layer bath proved to be more suitable than electrochemical polymerization. The upper organic layer of the electrolytic bath is a dilute solution of a polymer in an orgaific solvent, sometimes, supplemented with a small amormts of surfactant. The polymer interacts with the nascent colloidal metal particles near the interface between layers. 

Less often, nanoparticles are formed on polymers by means of electrophoretic and electrochemical deposition of metals onto an added polymeric suspension. The metallopolymer formation results from the polarizational of polymer and metal particles during deposition on the electrode followed by chemisorption of macromolecules at the metal sinface at the moment of its reduction. This process includes 

Polymeric particles shield and block, the surface of the electrode and metal particles. Therefore, electrophoretic polarization appears, which has an appreciable effect on the process of metal electrocrystallization. The polymer is often deposited as a separate phase (liquid or solid) on the electrode surface. The polymer may cause significant kinetic restrictions to the transfer of ions, electrons, or neutral particles through this new layer. The extent of those restrictions depends on the permeability of polymeric coating. Coating the anode with an insulating polymer layer reduces the electrode activity and the current amplitude. This inconvenience can be partly eliminated by the use of liquid electrodes, such as the dropping mercury electrode. 

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E. Electrochemical Methods for Preparing Polymer-Immobilized Nanoparticles... 

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