Synthesis of end-functionalized oligomers by one-batch cationic polymerization

The synthesis of end-functionalized oligomers by cationic polymerization is examined. Special attention is devoted to the problem of achieving this sy nthesis in a one-batch process, starting from the monomer and an additive w hich is properly functionalized. The functions of interest are chosen among the pseudohalide functions, azide and isothiocyanate. The functionalizing cationic polymerization of 2-methylpropene was the main system discussed in this context. A brief mention about the behavior of 1,3-pentadiene, isobut ylvinylether, and 2-methyl-2-oxazoline is presented. It is shown that depen ding upon the strength of the Lewis acid and the experimental conditions, t he specificity of the functionalization and the possibility of a controlled polymerization can be obtained. The experimental observations can be ratio nalized by assuming an equilibrium between the active species and the dorma nt chain ends containing a halide or a pseudohalide. This assumption allows to explain the synthesis of polymers containing two different types of cha in termini but corresponding to a narrow molecular weight distribution.