BLOCK COPOLYMERS OF POLYACETALS

The polymerization of 1,3‐dioxolane was carried out using trifluoromethanesulfonic acid (triflic acid) as catalyst, in the presence of an oligomeric diol, α‐hydro‐ω‐hydroxypoly(oxyethylene) (PEOG) or α‐hydro‐ω‐hydroxypoly(oxytetramethylene) (poly‐THF‐diol). When PEOG was used, a linear increase of the number average molecular weight versus conversion was observed. A triblock copolymer was obtained as well as small cycles in their usual equilibrium concentration. When poly‐THF‐diol was used, fast transacetalization provoked the “polycondensation” of the diol through acetal linkages at the very onset of the reaction, leading to a very inhomogeneous mixture. After equilibrium was reached, through reactions involving all the various species present, a triblock copolymer was also obtained. In conclusion, this method is well suited to prepare α,ω‐diol block copolymers in which the initial oligomeric diol constitutes the center block, while the outside blocks are made of polyacetal. Copyright © 1990 Hüthig & Wepf Verlag