Polypropylene transition metal ions

As it was demonstrated by staining the oxidized polypropylene and its observation by UV microscope, a high degree of inhomogeneity at the micron level was observed even for the most thoroughly annealed samples. In most cases this is clearly associated with the catalyst residues. An observation of microdomains in the oxidized polymer in which the degree of oxidation is by far pronounced than in the rest of polymer may be explained by the effect of higher oxidation state of transition metal ions M which interact directly with polymer ... 

The polymers obtained by polymerization in the presehce of metal catalysts contain metal residues which cannot be removed so readily. It is also well known that transition metal ions act as sensitizers for the photooxidation of polyolefins (29). Kujirai et al. (30) found that photodegradation of polypropylene depends on the oxygen concentration and on the residues of the polymerization catalyst, and they concluded that oxidative photodegradation is sensitized by the initiator metal residues (ash). Very recently Scott (31) used transition metal ions as sensitizers to develop photodegradable polymers. 

Reaction of the parent amine with transition-metal ions is also a possibility. The hindered piperidines have also been found to inhibit the photolysis of luminescent a,/3-unsaturated carbonyl groups (impurities) in polypropylene. 

Catalysts used in the polymerization process. For example, commercial isotactic polypropylene is polymerized from a hetereogenous organo-aluminium-titanium complex (Ziegler-Natta process) [110,1260], or less frequently from metallic oxides of chromium, vanadium or molybdenum bonded to an inert support (e.g. the Philips process) [447]. Transition metal ion contents vary in different commercial samples (Table 2.4). 

Allen, N.S., Fatinikun, K.O., Henman, T.J. Influence of transition metal ions on the photo-behaviour of BHT in polypropylene UV-study. Polym. Degrad. Stab. 17, 81-88 (1987)... 

The syndiotactic polypropylene has a melting point up to 133°C (2 74). (Me2C(Flu)(Cp))ZrCl2 and similar metallocenes, in combination with MAO or other perfluorinated borates, can produce chiral metallocenium ions in which chirahty is centered at the transition metal. Because of the flipping of the polymer chain, the metallocene alternates between the two enantiomeric configurations and produces a syndiotactic polymer (272, 175). It had not previously been possible to produce such pure syndiotactic polymer. 

In its most classic structure, a lithium-ion (Li-ion) battery contains a negative electrode made of carbon graphite, a positive electrode made of a layered oxide LiM02 (M transition metal, e.g. LiCo02) and a polypropylene separator soaked in an electrolyte made of a lithium salt (e.g. LiPFe) dissolved in a mixture of alkyl carbonate organic solvents (e.g. ethylene carbonate-dimethyl carbonate (EC-DMC)). The reversible electrochemical process is as follows ... 

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