Copolymers pyrroles

Many synthetic latices exist (7,8) (see Elastomers, synthetic). They contain butadiene and styrene copolymers (elastomeric), styrene—butadiene copolymers (resinous), butadiene and acrylonitrile copolymers, butadiene with styrene and acrylonitrile, chloroprene copolymers, methacrylate and acrylate ester copolymers, vinyl acetate copolymers, vinyl and vinyUdene chloride copolymers, ethylene copolymers, fluorinated copolymers, acrylamide copolymers, styrene—acrolein copolymers, and pyrrole and pyrrole copolymers. Many of these latices also have carboxylated versions. 

Figure 11. Cyclic votammetry (top) and in situ electronic conductivity from rotating-disk voltammetry [ , Fig. 9(C)] and sandwich electrode voltammetry [ , Fig. 9(B)] for poly(3-methylthiophene) in acetonitrile containing 0.1 M BU4CIO4.60 (Reprinted from J. Ochmanska and P. G. Pickup, In situ conductivity of poly-(3-methylthiophene) and (3-methylthiophene)x,-[Ru(2,2 -bipyridine)2 (3- pyrrol-l-ylmethyl pyridine)2]2+ copolymers, J. Electroanal. Chem. 297, 211-224, 1991, with kind permission from Elsevier Sciences S.A.)...

Anionic polymerization of lactams was shown to proceed according to what is called the activated monomer mechanism. With bischloroformates of hydroxy-terminated poly(tetramethyleneglycol) and poly(styrene glycol) as precursors for a polymeric initiator containing N-acyl lactam ends, block copolymers with n-pyrrol-idone and e-caprolactam were obtained by bulk polymerizations in vacuum at 30 and 80 °C, respectively361. ... 

Pyrrole derivatives substituted in positions 1-, 3-, or 4- have also been electrochemically polymerized (positions 2- and 5- must be free for polymerization). Besides homopolymers, copolymers can also be prepared in this way. Other nitrogen heterocycles that have been polymerized by anodic oxidation include carbazole, pyridazine, indole, and their various substitution derivatives. 

A large number of different pyrrole-based polymers have now been electrochemically synthesised, using a variety of conditions, and these are summarised in Table 2, although it should be noted that the size of this field and its rate of growth mean that it is impossible to make such a table completely comprehensive, and that reports of related new materials, particularly of copolymers incorporating pyrrole are continually appearing in the literature. Water-soluble polypyrroles have also recently been reported [246],... 

The formation of inter- and intrapolymer complexes has also been shown to affect the polymerization kinetics. For example, Ferguson and Shah (1968) investigated the influence of intrapolymer complexation on the kinetics of AA in the presence of copolymer matrices composed of either A-vinylpyrrolidone and acrylamide or A--vi nyl pyrrol idone and styrene. The polymerization rate reaches a maximum in the vicinity of AA to VP ratio equal to one for the VP/AAm matrix. This maximum in the polymerization rate is most pronounced in the presence of copolymer with the highest content of VP. When the hydrophilic acrylamide is replaced with the more hydrophobic styrene monomer in the copolymer matrix, the observed maximum in AA polymerization rate occurred at a lower than equimolar ratio of AA to VP. The hydrophilic groups of VP were interacting with the hydrophobic nucleus consisting of the styrene units in the VP/St copolymer, and were thus unable to participate in the formation of the complex unlike in the case of VP/AAm copolymer matrix. 

Following the discovery of the unique electronic properties of polypyrrole, numerous polymers of pyrrole have been crafted. A copolymer of pyrrole and pyrrole-3-carboxylic acid is used in a glucose biosensor, and a copolymer of pyrrole and A-methylpyrrole operates as a redox switching device. Self-doping, low-band gap, and photorefractive pyrrole polymers have been synthesized, and some examples are illustrated [1,5]. 

Several approaches have been undertaken to construct redox active polymermodified electrodes containing such rhodium complexes as mediators. Beley [70] and Cosnier [71] used the electropolymerization of pyrrole-linked rhodium complexes for their fixation at the electrode surface. An effective system for the formation of 1,4-NADH from NAD+ applied a poly-Rh(terpy-py)2 + (terpy = terpyridine py = pyrrole) modified reticulated vitreous carbon electrode [70]. In the presence of liver alcohol dehydrogenase as production enzyme, cyclohexanone was transformed to cyclohexanol with a turnover number of 113 in 31 h. However, the current efficiency was rather small. The films which are obtained by electropolymerization of the pyrrole-linked rhodium complexes do not swell. Therefore, the reaction between the substrate, for example NAD+, and the reduced redox catalyst mostly takes place at the film/solution interface. To obtain a water-swellable film, which allows the easy penetration of the substrate into the film and thus renders the reaction layer larger, we used a different approach. Water-soluble copolymers of substituted vinylbipyridine rhodium complexes with N-vinylpyrrolidone, like 11 and 12, were synthesized chemically and then fixed to the surface of a graphite electrode by /-irradiation. The polymer films obtained swell very well in aqueous... 

A low band-gap (Eg 1.6 eV) conjugated thiophene copolymer 468 with pyrrole and BT units was synthesized by Stille coupling [568]. They showed emission in the NIR region (AEL 800 nm) with turn-on voltage below 4 V but with very low efficiency (Chart 2.113). 

Bruno FF, Fossey SA, Nagarajan S, Nagarajan R, Kumar J, Samuelson LA (2006) Biomimetic synthesis of water-soluble conducting copolymers/homopolymers of pyrrole and 3,4-ethylenedioxythiophene. Biomacromolecules 7(2) 586-589... 

Polymerization (76MI11100) of the maleimide isomer 5-(l-adamantyloxy)-2//-pyrrol-2-one (11) allows incorporation (Scheme 6) of the 4-pyrrolin-2-one ring system into a polymeric framework. In analogy with model compounds, polymers and copolymers containing the structural unit (12) undergo photochemical rearrangement to the isocyanate structure (13). Thermolysis, on the other hand, produces poly(maleimides) (14). 

Because their oxidation potentials are similar, substituted pyrroles can be copolymerized with pyrrole, allowing the limiting conductivity of the fully-doped polymer to be varied 194,19S). The oxidation potentials of the monomers, and hence their reactivity ratios, are sensitive to the substituent196). Inganas et al.197) reported the synthesis of pyrrole-thiophene copolymers starting from terthiophene, whose oxidation potential is similar to that of pyrrole. Sundaresan et al.198) copolymerized pyrrole with 3-(pyrrol-l-yl)propanesulphonate to give a polymer in which the sulphonate counter-ion is a part of the polymer structure. 

Because of the problems associated with copolymerizations of monomers of very different reactivity, many authors have looked at an alternative approach which is to synthesise appropriate sections of the desired polymer chain, then couple them electrochemically to get the final polymer. Naitoh et al.199) synthesised the dimer, 2,2 -thienylpyrrole and used this as a monomer to prepare the alternating pyrrole-thiophene copolymer. They claimed that the copolymer film obtained with HSO as the counter-ion is more conductive than either of the corresponding homopolymers by a factor of 10 to 20. McLeod et al. 200) synthesised 2,5-dithienylpyrrole and polymerized it electrochemically with silver p-toluenesulphonate as the electrolyte. They obtained films of polymer whose conductivity could be varied in the range 10 8 to 0.1 Scm-1. Surprisingly, some low conductivity films were soluble in acetone or acetonitrile and evaporation of the solvent gave a powder of similar conductivity. Based on the shift in the absorption maximum in the visible spectrum on polymerization, it was concluded that the soluble films were polymers with molecular weights of 4000. 

Fig. 26.2. Amperometric immunosensors set-up using a biotinylated copolymer poly(pyrrole-biotin, pyrrole-lactitob-ionamide) coated platinum or glassy carbon electrodes and three enzymatic markers (GOX-B, PPO-B, HRP-Ab) for the detection of cholera antitoxin. (A) HRP-immunosensor, (B) GOX-B-immunosensor, (C) PPO-B-immunosensor. Mred/Mox = hydroquinone/quinone Gox = biotinylated glucose oxidase PPO — biotinylated polyphenol oxidase HRP-Ab = peroxidase-labeled IgG anti-rabbit antibody.

The synthesis, characterization, electrical conductivity, and field effect mobility of a series of novel soluble N-alkyl dithieno[3,2-b 2, 3 -d]pyrrole (DTP) and thiophene (TH)-based copolymers (DTP-co-THs) were reported (06MM1771 08JA13167). The incorporation of DTP units extends n conjugation, and the introduction of thiophene subunits imparts good solubility, high conductivity, and high charge carrier mobility. Therefore, the incorporation of DTP units and various substituted thiophenes into the polymer backbone affords the ability to enhance the solubility, lower the band gap, and achieve the enhanced electronic properties. 

Other early work in this field included the use of tetrakis(p-aminophenyl)-porphyrin (Fig. 7a), which was electrodeposited onto glassy carbon and showed a near-Nernstian response to iodide [76]. Electrodeposited methylthiophene-methylpyrrole copolymer was deposited and shown to give a near-Nernstian response to bromide [77]. Pyrrole-3-boronate (Fig. 7b) could be deposited to give films with a good response and marked selectivity to fluoride [78]. A cobalt aminophthalocyanine could also be electropolymerised to give a good sensor for nitrite [79] or sulphide ion [80]. 

Perhaps the original hope for these polymers was that they would act simultaneously as immobilisation matrix and mediator, facilitating electron transfer between the enzyme and electrode and eliminating the need for either O2 or an additional redox mediator. This did not appear to be the case for polypyrrole, and in fact while a copolymer of pyrrole and a ferrocene modified pyrrole did achieve the mediation (43), the response suggested that far from enhancing the charge transport, the polypyrrole acted as an inert diffusion barrier. Since these early reports, other mediator doped polypyrroles have been reported (44t45) and curiosity about the actual role of polypyrrole or any other electrochemically deposited polymer, has lead to many studies more concerned with the kinetics of the enzyme linked reactions and the film transport properties, than with the achievement of a real biosensor. 

Copolymers of furfural with pyrrole have been reported to yield carbon fibers of remarkable quality (22). More recent reports include the use of poly(N-vinylcarbazole) with furfural and furfural-amine copolymers (23) to make both cation/anion exchange resins. A considerable amount of additional work needs to be done in this area to determine the commercial usefulness of such systems. 

N-Nitrosation (in sodium nitrite solution in HCl) of copolymers from pyrrole and 2-ethylaniline, easily prepared by oxidative copolymerization, has been done for the improvement of their solubility (Equation 60) <2004PLM385>. 

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