New polymer syntheses. 100. Multiblock copolyesters by combined macrocyclic polymerization and silicon-mediated polycondensation

Using 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP) as cyclic initiator the macrocyclic polymerizations of epsilon-caprolactone were conducted in bulk at 80 degrees C at monomer/initiator ratios of 20/1. The resulting tin-containing supermacrocycles were reacted in situ with an excess of isophthaloyl chloride, and this reaction mixture was polycondensed with silylated Bisphenol A at temperatures between 150 and 300 degrees C. The characterization of the isolated copolyesters by DSC measurements and H-1 NMR and C-13 NMR spectroscopy proved that they possess a perfect multiblock structure up to a reaction temperature of 240 degrees C. At higher temperatures transesterification causes a more or less perfect randomization of the sequence. In a second series of combined ring-opening polymerizations and ring-opening polycondensations (ROPPOC) silylated methylhydroquinone and 1,10-bis(4-chlorophenoxy)decane were used as comonomers of the macrocyclic poly(epsilon-caprolactone). The isolated multiblock copolyesters showed a two phasic melt with an isotropic phase containing the polylactone blocks and a nematic phase consisting of the aromatic blocks. The relationship between block lengths and phase separation is discussed.