Polymethylmethacrylate effect radicals

The sample irradiated at — 196° C in the presence of air gave the same spectrum as that under vacuum. This sample, however, gave the spectrum characteristic of peroxy radicals at about — 68° C. An effect of oxygen on radical formation on irradiation with light of 300 nm was also reported (67). Protection against radiation damage in polymethylmethacrylate by ultraviolet light was also reported (98). 

Isotactic polymethylmethacrylate has been shown to isomerize into the atectic form under the effect of electrons [404] or 7-rays [405]. The yield of isomerization is higher with ionizing radiation than with UV irradiation [405], as is the main-chain scission yield the G value for volatile formation, on the other hand, is lower for 7 than for UV irradiation. The isomerization has therefore been attributed to main-chain scission followed by recombination of the radicals in the cage. This isomerization is completely inhibited in the presence of ethyl mercaptan [406]. 

Polyaniline-ZnO nanocomposites were synthesized by in-situ oxidative polymerization of aniline monomer in the presence of different amounts of ZnO nanostructures. ZnO nanostructures were prepared in the absence and presence of surfactant. The effect of ZnO nanostructure concentration on the conducting behaviour of nanocomposites was evaluated by a two-probe method. The results showed that the conductivity of nanocomposites was increased with an increased concentration of ZnO nanostmctures as compared with neat polyaniline. Optimum conductivity was observed with incorporation of 60% ZnO nanostructures into the polyaniline matrix [248].Polymethylmethacrylate-ZnO nanocomposites were fabricated by solution radical copolymerization of methyl methacrylate and oleic acid-modified ZnO nanoparticles using 2,2 -azobisisobutylonitile as initiator in toluene. The UV-vis analysis showed that resulting nanocomposites exhibited high absorption in the ultraviolet region and low absorption in the visible region [249]. 

Several types of polymers degrade primarily by a free radical depolymerisation including polystyrene and polymethacrylate. When a free radical is produced in the backbone of polymethylmethacrylate, for example, the molecule undergoes scission to produce an imsaturated small molecule (ethyl methacrylate) and another terminal free radical. This radical will also cleave to form ethyl methacrylate and propagate a free radical. The net effect is often referred to as imzipping the polymer. 

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