Radical polycation

For the QPh-x-MV2+ system, the methylviologen cation radical (MV K) generated by laser photolysis decayed with a rate constant of kb = 3.2 x 108 M-1 s-1. This relatively strong retardation of the back ET is due to the electrostatic repulsion of MV + by the polycation [76]. 

Cai et al. [7e] investigated electron and hole transfer in various polynucleotide duplexes and compared them with previous results found for salmon sperm DNA, to examine the effect of base sequence on excess electron and hole transfer along the DNA 71-way at low temperature. Electron and hole transfer in DNA was found to be clearly base sequence dependent. In glassy aqueous systems (7M LiBr glasses at 77 K), excess electron-transfer rates increase in the order polydIdC-polydIdC<salmon testes DNAexcess electron and hole transfer rates increase in the order polyC-polyG<salmon testes DNATransfer distances at 1 min and distance decay constants for electron and hole transfer from base radicals to MX in polynucleotides-MX and DNA-MX at 77 K are derived and compiled in Table 3. This table clearly shows that the electron-transfer rate from donor sites decreases in... 

The most desirable properties for electrically conductive polymeric materials are film-forming ability and thermal and electrical properties. These properties are conveniently attained by chemical modification of polymers such as polycation-7, 7,8, 8-tetracyanoqninodimethane (TCNQ) radical anion salt formation (1-3). However, a major drawback of such a system is the brittle nature of the films and their poor stability (4,5) resulting from the polymeric ionicity. In recent years, polymeric composites (6-8) comprising TCNQ salt dispersions in non-ionic polymer matrices have been found to have better properties. In addition, the range of conductivities desired can be controlled by adjusting the TCNQ salt concentration, and other physical properties can be modified by choosing an appropriate polymer matrix. Thus, the composite systems are expected to have important advantages for use in electronic devices. 

Spectrophotometric titration data imply the formation of stable HPA-polyelec-trolyte complexes. On average, 3—3.5 monomer polycation units correspond to one heteropolyanion. Immobilized HPA maintains specific properties of homogeneous HPA solutions. For instance, thqr are capable of both chemical and photochemical reduction. By addition of a Cr q solution to the polymeric complex suspensions, or by ultraviolet irradiation of this suspension, the complexes acquire a reddish tint which indicates the formation of a reduced species of HPA. The ability of highly-reduced HPA species to evolve H2 is attributed to the presence of multi-valenced cations in HPA e.g. W, Mo, etc.) that promote the double-electron reduction of water to H2 without evolution of free radicals. 

The same is true for other polymer modification reactions with acrylamide derivatives especially cationic structures for the formation of cationic surface layers. Furthermore acrylamide derivates like methylenediacrylamide are used in various polymerisation reactions and have to be determined in polymer solutions. The polycations formed by a radical polymerization and their reaction products with polyanions (symplexes) have to be characterized when they are used in polymer modification or other fields. 

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