Light absorbing impurities in polymers

Industrially produced polymers contain a number of light-absorbing impurities produced in side-reactions during polymerization, processing and storage. These impurities can be divided into two groups [1759,1766,1768]  

Internal impurities which contain chromophoric groups, introduced into macromolecules during polymerization, processing and storage, including  

Anomalous structural units such as branching, which originate in the polymerization process. 

Catalyst residues attached to chain ends of macromolecules. 

Charge-transfer complexes with oxygen (cf. section 2.15). 

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