MACROCYCLIC POLYMERIZATION - A NEW APPROACH TO MOLECULAR ENGINEERING

2,2-Dibutyl-2-stanna-1,3-dioxacycloalkanes were used as cyclic initiat ors for the ring-opening polymerization of various lactons. This metho d exclusively yielded series of macrocyclic polylactones without any c ompetition with linear polymers. Under optimized reaction conditions t hese macrocyclic polymerizations obey the pattern of ''living polymeri zations''. The living chain ends allow the syntheses of macrocyclic bl ockcopolymers. The macrocyclic polylactones react with carboxylic acid chlorides by ring-opening yielding telechelic oligo or polylactones. Furthermore, the tin containing macrocyclic polylactones can be used a s difunctional ''monomers'' for polycondensations with dicarboxylic ac id dichlorides.