Extending the Methylene Spacer Length of ADMET Hydroxy-Functionalized Polymers

Abstract

Solution acyclic diene metathesis (ADMET) polymerization using Grubbs' first-generation catalyst leads to the direct synthesis of polymers containing hydroxyl groups. Secondary alcohols are placed precisely at specific intervals on an unsaturated hydrocarbon backbone. Increasing the number of methylene spacers decreases the frequency of the pendant groups from every 15th carbon to every 21st carbon. The complete hydrogenation of the unsaturated polymers yields model representatives of well-defined ethylene–vinyl alcohol copolymers. Despite the decrease in branch frequency in both the homopolymers and randomized versions of such polymers, surprisingly, the precision does not have an influence on the thermal properties, and they are all similar in nature. It is concluded that hydrogen bonding dominates the polymer behavior, rather than the precision in hydroxyl-group placement along the polyethylene chain.