Transfer agents and retarders

Analysis of the NMR spectrum of a polymer made under these conditions can give information about the stereochemistry of two or three of the dyads at the end of the chain. When methyl iodide terminates the anionic polymerization of MMA, the resulting terminal unit is -CH2 CMe2 COOMe which resembles that produced when a particular azo ester is used as a radical initiator for the monomer (see section 3.2.2). 

The presence of hydroxyethylmercapto end-groups in the derived poly(vinyl alcohol) was confirmed by H NMR for a sample of polymer with a number-average degree of polymerization of about 80. Similar experiments involving n-alkyl mercaptans up to C gH37SH gave comparable results [51]. 

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