Mainchain scission

Figure 27. Mechanism of radiation induced chain scission in PMMA. Homolysis of the mainchain-carbonyl carbon bond is indicated as the initial step. Acylcarbon-oxygen, sigma bond homolysis also occurs but rapid decarbonylation ultimately leads to the same indicated products.

The efficiency of these polymer reactions is affected by the reagents and the reaction conditions, which ranged from 70 to 100%. In the cases of polymer reactions that do not proceed in a quantitative fashion, no distinct decrease of the molecular weight of the produced polymers were observed because the lower efficiency of the polymer reactions does not mean the scission of the mainchain of the polymers but the conversion into other structures such as the cyclobutadienecobalt imit. 

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