WELL-DEFINED ETHYLENE VINYL ALCOHOL COPOLYMERS VIA HYDROBORATION - CONTROL OF COMPOSITION AND DISTRIBUTION OF THE HYDROXYL-GROUPS ON THE POLYMER BACKBONE

Cyclic olefins having different ring sizes were polymerized by ring-opening metathesis polymerization to give polyalkenylenes that have double bonds separated by varying numbers of methylene units. Upon hydroboration followed by oxidation, these polyalkenylenes yielded ethylene-vinyl alcohol copolymers whose vinyl alcohol content varied from 16 to 50 mol %. The H-1 NMR and C-13 NMR spectra of these copolymers confirmed their structure and indicated that the hydroboration-oxidation reaction sequence was complete. Because of the absence of branching in these copolymers, they represent copolymers of linear polyethylene and vinyl alcohol. This is unlike the commercially manufactured ethylene-vinyl alcohol copolymers, which have branching. The melting points of these copolymers were found to go through a minimum at a composition of approximately 40 mol % vinyl alcohol. At higher ethylene content the melting point approaches that of linear high-density polyethylene. Since this approach allows the complete control of both the composition and the spacing between the hydroxyl groups on the polymer backbone, these copolymers serve as excellent models for understanding the structure-property relationship in such systems.