REDOX POLYMERISATION

Polymerisation reactions utilising such redox initiators are termed redox polymerisation. ... 

We have already come across a few examples in which oxidation-reduction reaction can initiate vinyl polymerisation. Such a polymerisation reaction is known as redox polymerisation. In such reactions the oxidant is generally referred to as initiator and the reductant as activator. 

McArdle, C., Burke, J., and McGettrick, B., Characterisation of cure distribution in surface initiated redox polymerisation by DM and di-electric thermal analyses. Plastics. Rubber Composites Processing Applications. 16, 245-253 (1991). 

Redox polymerisations of acrylic acid in inverse dispersion and in aqueous solution (surfactant) were carried out using sodium metabisulphite/potassium bromate initiators. Experimental rate expressions indicated that complex reactions were involved in the polymerisations. A chemical reaction scheme was suggested and kinetic models were developed for the redox polymerisation in aqueous solution. Differences in the experimental rate expressions between the redox polymerisation in inversion dispersion and that in aqueous solution agreed well with the kinetic model predictions. 23 refs. 

Because the monomers used are water soluble, polyacrylate dispersing agents are manufactured by redox polymerisation directly in water. 

The redox potential and the reactivity of this oxidation state depend strongly upon the anion (Table 11). Strong complexes are formed with SO ". Even in perchloric acid, hydrolysis and polymerisation greatly complicate kinetics. The co-ordination number of Ce(lV) in solution is not established . 

Initiation. Initiation in radical polymerisation consists of two steps the dissociation of the initiator to form two radical species, followed by addition of a single molecule to the initiating radical (Figure 18). Initiators include any organic compound with a labile group, such as an azo (-N = N-), disulfide (—S—S—) or peroxide (-0-0-) compound. The labile bond can be broken by various ways like heat, UV light, /-irradiation or by a redox reaction. 

POLYCONDENSATION REACTION INCIDENTS, POLYMERISATION INCIDENTS, REDOX REACTIONS, SULFONATION INCIDENTS... 

Muller and co-workers have prepared the first reported tetrathiafulvalene (TTF) main chain polymer which they suggest may improve metallic and redox properties of the material due to improved through-bond and through-space interactions in the solid state <1999CC1407>. They also report a simple synthesis of the polymeric material via a novel oxidative polymerisation sequence as outlined in Scheme 18. 

The Cu(II)/Cu(I) redox system added as bromide has recently been used to prepare well-defined polymers (controlled molecular weight, reduced poly-dispersity, terminal functionalities). One of the most successful methods to make well-defined polymers is atom transfer radical polymerisation (ATRP)18 ... 

In the hrst step, a redox reaction occurs between Ce(IV) and the -CH2OH end group of PEO, generating a free radical in a-position of the -OH group of PEO. In a consequent step, the radical is transferred from the PEO chain to the vinyl monomer. The radicals formed initiate the actual polymerisation reaction (propagation) ... 

NITRATION INCIDENTS OXIDATION INCIDENTS PEROXIDATION INCIDENTS PLANT CLEANING INCIDENTS POLYCONDENSATION REACTION INCIDENTS POLYMERISATION INCIDENTS REDOX REACTIONS SULFONATION INCIDENTS... 

Polyatomic ions (as opposed to neutral molecules) may also be unstable with respect to decomposition, polymerisation or disproportionation. However, ions cannot be scrutinised in isolation. In a crystalline solid, there are always counter-ions of opposite charge to be considered, and in solution an ion is surrounded by solvent molecules. The intimacy of the chemical environment of any ion must influence its viability. For example, redox reactions involving electron transfer between cation and anion, or between ion and solvent, may find easy kinetic pathways. We look here at some examples of unstable oxoanions. 

A wide range of dendrimers with functional core is described in the literature. Thus chromophores [7], electrochemically active, redox active [8], and catalyti-cally active [9] or also self-associating and chiral units as well as polymerisable monomers and polymers have been successfully introduced into the centre of dendrimers. However, the core unit not only has a determining effect on the function, but also has a decisive influence on the multiplicity, size, and shape of the dendrimer. 

In the early 1970s, surface modification of most polymers was achieved using redox initiators. Ce+4-induced initiation was employed to achieve surface grafting of acrylamide onto LDPE film [117]. The film was first oxidised by chromic acid and then reduced with diborane to form a hydroxyl-rich surface which was then used to initiate graft polymerisation of acrylamide using Ce+4/HN03. The mechanism of chromic-acid-facilitated surface oxidation of LDPE surface is shown in Scheme 6a and that of free-radical generation is represented in Scheme 6b. 

Polyrotaxanes have been prepared by threading multiple a-cyclodextrin units onto a bulky benzimidazole-based linear chain polymer with an aliphatic spacer where the cyclodextrin resides. The rotaxane forms as the cyclodextrin-bound precursor amine is polymerised. Compared to the polymer in the absence of the cyclodextrins, the glass transition temperature is raised by some 20 °C even though only ca. 16 % of the aliphatic spacers in the polymer are rotaxanated.28 A novel approach to polyrotaxanes involved the use of a metal ion such as Zn2+ to thread a phenanthroline-based macrocycle onto a thiophene-based complementary monomer. The resulting pseudorotaxane can then be electropolymerised and the Zn2+ ions removed to give a polyrotaxane, Scheme 14.5. The redox and conductivity properties of the polymer are very much dependent on whether a metal ion is bound or not.29... 

Redox- and photo-initiation of free radical polymerisation found (Melville, Logemann, Kern, et al.)... 

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