Reactions mechanicochemical

Mechanicochemical reactions of various gases (e.g. H2O, NH3, NO, NO2, and CI2) with quartz have been carried out in a glass vibromill at 80 and 300 The quartz, normally accepted as being an inert mineral, was surprisingly reactive this was attributed to the formation of short-lived centres on freshly formed surfaces. 

Several methods can be used to synthesize block copolymers. Using living polymerization, monomer A is homopolymerized to form a block of A then monomer B is added and reacts with the active chain end of segment A to form a block of B. With careful control of the reaction conditions, this technique can produce a variety of well-defined block copolymers. This ionic technique is discussed in more detail in a later section. Mechanicochemical degradation provides a very useful and simple way to produce polymeric free radicals. When a rubber is mechanically sheared (Ceresa, 1965), as during mastication, a reduction in molecular weight occurs as a result of the physical pulling apart of macromolecules. This chain rupture forms radicals of A and B, which then recombine to form a block copolymer. This is not a preferred method because it usually leads to a mixture of poorly defined block copolymers. 

Mechanicochemical reactions can occur during processing, when the polymer is converted to a finished product. The chain scission can occur in both saturated and unsaturated polymer backbones. For example, during processing in a screw extruder, backbone scission in polypropylene produces long-tail... 

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