Autoinhibition autotermination

Chains with a double bond in their end group are formed by a reaction generating an alkali metal hydride (see Chap. 7, Sect. 3.1). 

The formation of the unreactive allylic ion causes growth termination of cationically polymerizing 2-methylpropene chains [108] 

The loss of the addition ability of an ion by delocalization of the electron defect in a conjugated polyene chain is documented by the observation of Subramanian et al. They polymerized monomers with C=C and C=N bonds by electroinitiation. Anionic polymerization of phenylacetylene started very easily but it rapidly died out without any external cause [109]. The polymerization of n-alkyl-2-cyanoacrylatet in the presence of tetracyanoethy-lene yields only low-molecular-weight products. This is due to the formation 

When the anionically produced polymer is more acid than the monomer, then the active centres are neutralized by protons dissociating from the chains. 

This kind of autotermination was described in the polymerization of m, / -and D. 6-dinitrostvrenes 

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