Electrochemical polymerization strategy

In conventional polymer synthesis copolymerization is a common strategy for modifying polymer properties. In electrochemical polymerizations of the kind used to make conducting structures, it is expected to be difficult to make good copolymers unless the oxidation potentials of the two monomers are sufficiently close that one is not significantly preferred over the other 190). 

Electrochemical polymerization of pyrrole on an SWNT electrode using an aqueous HCl 0.5 M solution as electrolyte, resulted in deposition of a PPy film onto the SWNT layer leading to a composite with a bilayer structure, as demonstrated by Raman spectroscopy [112]. Anew method was developed by S.Cosner eta/, in 2008 [111] SWNTs were functionalized by electropolymerizable pyrrole groups following covalent and noncova-lent strategies. The covalent pyrrole grafting was carried out by ester formation between pyrrole alcohol and chemically oxidized SWNTs. The strong Ti-interactions between pyrene and SWNTs were exploited for the noncovalent adsorption of a new pyrene-pyrrole derivative on the pristine CNT surface. The pyrrole-ester-SWNTs were solubilized in THE and electropolymerized by controlled potential electrolysis at 0.95 V. The PPy/SWNT... 

The group also proposed a novel one-step electrochemical composite polymerization strategy for the first to prepare unique PPy/reduced GO/ carbon nanotubes (PPy/F-RGO/CNTs) ternary composites, where F-RGO,... 

Electrochemical polymerization provides a convenient approach to fabricate CNTs/CP nanocomposites [46-53], Using such a strategy, the morphology and properties of the nanocomposites can be controlled by the electropolymerization conditions, such as the applied potential or current density. Ajayan and co-workers have reported the electrochemical oxidation of aniline in H SO on the CNTs electrode to fabricate CNT/PANl composites [46]. Chen et al. fabricated CNT/PPy nanocomposites, the first example of anionic CNTs acting as the dopant of a CP [47]. Their results showed that PPy was xmiformly coated on the surface of individual CNTs by electrolysis at a low apphed potential for a short time, rendering them potential applications in nanoelectronic devices. Another kind of CNTs/CP composite nanostructures, e.g., CNTs as inorganic fillers in CP matrices [54] can be prepared by a template-directed electropolymerization method. (Figure 13.3)... 

Shi et al. have developed another method for the electrochemical polymerization of high oxidation potential monomers in boron fluoride ethyl ether (BFEE) which could yield highly conducting PT films (Scheme 9.4) [32]. As observed in the case of the electropolymerization of 3-methylthiophene, bithiophene 2T and terthiophene 3T, such improvement stems from the lower oxidation potentials at which the electropolymerization occurs in BFEE compared with those required in common electrolytes. Recent development of this strategy by the Reynolds group has shown that thiophene, 3-methylthiophene, 3-bromothiophene and 3,4-dibromothiophene can be polymerized in BFEE to yield homogeneous, electroactive polymer films, where their electrochemical polymerization in common electrochemical solvents has proved much more difficult [33],... 

Flowever, the focus of the major part of the chapters lies on the couphng chemistry used for DNA immobilization. Successful immobihzation techniques for DNA appear to either involve a multi-site attachment of DNA (preferentially by electrochemical and/or physical adsorption) or a single-point attachment of DNA (mainly by surface activation and covalent immobihzation or (strept)avidin-biotin linkage). Immobilization methods described here comprise physical or electrochemical adsorption, cross-linking or entrapment in polymeric films, (strept)avidin-biotin complexation, a surface activation via self-assembled monolayers using thiol linker chemistry or silanization procedures, and finally covalent coupling strategies. 

The EQCM technique not only provides a sensitive piezoelectric platform for mass and energy dissipation detection, but also an electrochemical means for quantitating electron transfer processes and for creating polymeric surface films. Such films are valuable for creating biosensors since they can be designed for the immobilization of biological components. As we illustrated in Sect. 3, the EQCM provides a valuable tool to monitor the formation and properties of polymer films formed via electropolymerization strategies. 

A vast literature exists describing numerous strategies for the adsorption and binding of electroactive molecules to electrode sur ces. Of those, the most commonly employed are covalent binding, polymerization, and self-assembly [2 - 5]. In this section, we briefly discuss the utility of these three immobilization techniques for studying redox-active species by STM and electrochemical STM, and present examples from our own studies. 

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