Poly exchange reactions

The reduced poly-[Fe(II)TPP] porphyrin site now finds itself next to a fresh poly-[Fe(III)TPP(X)] site one polymer lattice unit further into the polymer. An electron hopping - or self exchange - reaction can then ensue, repeatedly, in successive layers and sites ... 

The reaction amounts to a vectorically directed current in the sense of occurring down a concentration gradient of reduced poly-[Fe(II)TPP] sites emanating from the reducing electrode/polymer interface. The magnitude of the current clearly conveys information about the rate of the poly-[Fe(III)TPP(X)] - poly-[Fe(II)TPP] self exchange reaction. 

The preparation of N-alkyl imides by exchange reaction of an imide with an alkyl amine was documented [104] well before the application of this chemistry to the preparation of polyimides [105], see Scheme 30. Although no experimental details are provided, the initial reaction of pyromellitimide with p,p-methylene dianiline in NMP takes place at reflux temperatures to apparently yield a poly(amic amide). Subsequent heating of this intermediate at elevated temperatures ( 300 °C) provides the desired polyimide with evolution of ammonia. The final polyimide is quoted to be thermally and chemically stable, however, no mechanical properties are given. 

A substrate functionalized with proper molecules can be used to anchor particles on its surface via surface exchange reaction, leading to controlled assembly of the particles. This self-assembly technique is known as molecule-mediated self-assembly and is commonly used for constructing various composite nanostructures [49-55]. Due to their excellent adhesion capability to various substrates, multifunctional polymers are routinely applied as templates to mediate the assembly of the particles. The assembly is carried out as follows a substrate is immersed into a polymer solution, and then rinsed, leading to a functionalized substrate. Subsequently, this substrate is dipped into the nanoparticle dispersion and then rinsed, leaving one layer of nanoparticles on the substrate surface. By repeating this simple two-step process in a cyclic fashion, a layer-by-layer assembled poly-mer/nanoparticle multilayer can be obtained. 

Homogeneous charge transfer can take place between chemically similar redox species of one redox couple, e.g., Fe3+ and Fe2+ ions in solution or ferrice-nium and ferrocene moieties in poly(vinylferrocene) films, the electron transfer (- electron hopping or electron exchange reaction) can be described in terms of second-order kinetics and according to the - Dahms-Ruff theory [viii-x] it may be coupled to the isothermal diffusion ... 

Exchange reactions with amines and thiols (X = N, S in Fig. 156) are the most studied (see below) however, interesting C-alkylations, - based on the rather unusual replacement by bis-aldehyde (402, Fig. 157) to give poly( 5-diketone)s 403, have also been performed. 

Polymeric macromoleculcs of types V-VII are needed for applications requiring enhanced molecular siite (see also Chap. III). Thus, linear polymers of type V are prepared by Mannich polymerization or from bis-Mannich bases by exchange reaction, for example, with bis-thiols, as in the case of poly(ketosulfide) 501, which is useful as a high-molecular-weight antioxidant in the processing of plastics.Macromolecules of type VI are generated by the functionalization of polymers, as shown by 502, which is obtained by aminomethylation of polyacrylamide and used as flocculant in water treatment." - ... 

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