Anionic conjugated polymer

Fig. 16 (a) Description of the detection of amyloid fibrils in proteins with an anionic conjugated polymer, PTAA. (b) Emission spectra (bottom) of PTAA-Native bovine insulin (filled square) and PTAA-amyloid fibrillar bovine insulin (x). (c) Kinetics of insulin amyloid fibril formation monitored by PTAA fluorescence [29]... 

Wang J, Liu B (2009) Fluorescence resonance energy transfer between an anionic conjugated polymer and a dye-labeled lysozyme aptamer for specific lysozyme detection. Chem Commun 17 2284—2286... 

Synthetic polymers can be classified as either chain-growth polymen or step-growth polymers. Chain-growth polymers are prepared by chain-reaction polymerization of vinyl monomers in the presence of a radical, an anion, or a cation initiator. Radical polymerization is sometimes used, but alkenes such as 2-methylpropene that have electron-donating substituents on the double bond polymerize easily by a cationic route through carbocation intermediates. Similarly, monomers such as methyl -cyanoacrylate that have electron-withdrawing substituents on the double bond polymerize by an anionic, conjugate addition pathway. 

In the area of ion sensing, cation recognition by electrodes containing functionalized redox-active polymers has been an area of considerable interest. Fabre and co-workers have reported the development of a boronate-functionalized polypyrrole as a fluoride anion-responsive electroactive polymer film. The electropolymerizable polypyrrole precursor (11) (Fig. 11) was synthesized by the hydroboration reaction of l-(phenylsulfonyl)-3-vinylpyrrole with diisopinocampheylborane followed by treatment with pinacol and the deprotection of the pyrrole ring.33 The same methodology was utilized for the production of several electropolymerizable aromatic compounds (of pyrrole (12) (Fig. 11), thiophene (13 and 14) (Fig. 11), and aniline) bearing boronic acid and boronate substituents as precursors of fluoride- and/or chloride-responsive conjugated polymer.34... 

Although the exact mechanism of the fluorenone formation is not known, it is believed that the monoalkylated fluorene moieties, present as impurities in poly(dialkylfluorenes), are the sites most sensitive to oxidation. The deprotonation of rather acidic C(9)—H protons by residue on Ni(0) catalyst, routinely used in polymerization or by metal (e.g., calcium) cathode in LED devices form a very reactive anion, which can easily react with oxygen to form peroxides (Scheme 2.26) [293], The latter are unstable species and can decompose to give the fluorenone moiety. It should also be noted that the interaction of low work-function metals with films of conjugated polymers in PLED is a more complex phenomenon and the mechanisms of the quenching of PF luminescence by a calcium cathode was studied by Stoessel et al. [300],... 

Zhang Y, Wang Y, Liu B (2009) Peptide-mediated energy transfer between an anionic water-soluble conjugated polymer and Texas red labeled DNA for protease and nuclease activity study. Anal Chem 81 3731-3737... 

Conducting polymers based on polymer chains with conjugated double bonds are electroactive materials that have found widespread use also in the field of chemical sensors [11-41], Oxidation of the conjugated polymer backbone is accompanied by anion insertion or cation expulsion, as follows ... 

As with the majority of ISEs, all of the aforementioned receptors are immobilised within close proximity to the transducer element. However, conducting polymers (electroactive conjugated polymers) are now emerging rapidly as one of the most promising classes of transducer for use within chemical sensors. Here, the receptor can be doped within the polymer matrix, i.e. within the transducer element itself. This will facilitate the production of reliable, cost-effective, miniaturised anion-selective sensors, as it will be possible to move away from plasticiser-based membranes, but allow for ion recognition sites in conjunction with all-solid-state ion-to-electron transducers. 

After a photon has excited the conjugated polymer to form an exciton, the C60 accepts one electron due to its high electron affinity and establishes the anion Cg0. What is left on the polymer chain is a cation radical, i.e., a positive polaron, as depicted in Fig. 1.14, which is a mobile charge carrier that can move along the polymer backbone. This transfer is an exothermal reaction, where energy from the system is released. 

Conjugated polymers may be made by a variety of techniques, including cationic, anionic, radical chain growth, coordination polymerisation, step growth polymerisation or electrochemical polymerisation. Electrochemical polymerisation occurs by suitable monomers which are electrochemically oxidised to create an active monomeric and dimeric species which react to form a conjugated polymer backbone. The main problem with electrically conductive... 

The unique property of conjugated polymers to uptake/release the anions upon transformation from oxidized to reduced state can be used for the targeted deposition of NPs. To demonstrate the principal viability of such approach, VCL/AAEM/PEDOT microgels have been used as templates for the incorporation of AuNPs [148], Figure20 shows the procedure of AuNP deposition into microgels filled with PEDOT nanorods. 

Using a different approach, the research gronps of Fabre and Freund have synthesized boronate-functionalized conjugated polymers, which serve as electrochemical sensors. For example, a conjugated redox-active film of polypyrrole (174) was electrodeposited onto a platinum electrode from acetonitrile solution. Addition of fluoride anions led to a new redox system that showed an anodic shift relative to polypyrrole itself, which was attributed to fluoride binding to the boronate group. A related poly(aniline boronic acid) (175) was also reported and studied for saccharide detection. " ... 

It has been mentioned already that polypyrrole (25) and polythiophene (26) play an important role as electrical conductors and polymeric anodes in battery cells [2,47,226]. Since the charging and discharging of the conjugated polymer is accompanied by the incorporation and removal of counterions it is clear that the material can also act as a carrier of chemically different anions which influence the physical, chemical and physiological properties of the material [292]. With regard to the full structural elucidation of the polymers it must be added, however, that the electropolymerization process of pyrrole and thiophene does not provide a clean coupling of the heterocycles in the 2,5-positions. Instead, the 3- and 4-position can also be involved giving rise to further fusion processes under formation of complex polycyclic structures [47]. 

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