Polymerization of N-Vinyl-2-Pyrrolidone under Anodic Polarization:  Characterization of the Modified Electrode and Study of the Grafting Mechanism

Abstract

The application of single step or multiple anodic potential steps to highly concentrated solutions of N-vinyl-2-pyrrolidone leads to the formation of poly(N-vinyl-2-pyrrolidone) (or PVP) films on platinum electrodes. These films are insoluble in a good solvent of the commercial polymer. Multiple potential steps yield thicker films than a single potential step. Moreover, the PVP film thickness is maximum for a working potential amplitude of 1.7 V. Above this potential, the polymer film deteriorates by oxidation. In situ quartz crystal microbalance measurements show that the formation mechanism of polymer films cannot be attributed to an initiation in solution followed by precipitation of the polymer on the surface but rather to a gradual growth of the polymer on the electrode. This result is confirmed by the analysis of the electrochemical medium by different techniques which does not reveal the presence of polymeric chains in solution but only of dimer molecules. The molecular structure and the origin of these molecules are precisely established. From these results, we conclude that the polymer is chemically bonded to the platinum at the interface and grows progressively on the electrode surface. Both a radical and a cationic mechanism are examined to explain the above observations. A detailed theoretical analysis of plausible reaction intermediates suggests that only the cationic mechanism is able to account for all present experimental results and, in particular, for the occurence of a voltammetric current during the polymer growth.

Electrografting: a powerful method for surface modification

“…158 Sequential electrodeposition of ethyl acrylate (EA) and acrylonitrile (AN) onto nickel has also been achieved. 159 It should also be noted that N-vinyl-2pyrrolidone, 150,[160][161][162] methacrylonitrile, 135 and 4-vinylpyridine 158 can also be polymerised by anodic oxidation on a Pt surface. The only restriction to cathodic electrografting is that the substituent should not be reduced before the vinyl group, for examples vinylic compounds with OH groups cannot be electrografted as the proton is reduced before the vinyl group.…”

Molecule‐to‐Metal Bonds: Electrografting Polymers on Conducting Surfaces

“…Fourth, an in situ study with an electrochemical quartz crystal microbalance (EQCM) on the electrografting of MAN and Nvinylpyrrolidone (NVP) in anhydrous acetonitrile under cathodic and anodic conditions, respectively, clearly showed that for the latter monomer, which is known to afford only the grafted polymer because the dimer formed after desorption of the grafted radical cation is highly stable, [39] the equivalent resistance of the quartz crystal electrode remains almost constant during electrodeposition. At the same time, the eigenfrequency of the quartz exhibits large variations.…”

Preparation and characterization of chitosan—Polyethylene glycol‐polyvinylpyrrolidone‐coated superparamagnetic iron oxide nanoparticles as carrier system: Drug loading and in vitro drug release study

“…Polyvinylpyrrolidone (PVP), a water‐soluble polymer with amphiphilic character, also possess outstanding features such as solubility, film and complex formation, adhesive and bonding power as toxicological harmlessness. This has led to an extensive investigation for varied prospective applications in the fields of cosmetics, pharmaceutical, medicine and industrial production …”