Maleation of poly(3,4-epoxy-1-butene) for accelerated crosslinking in the presence of a redox catalyst

Accelerated crosslinking of novel poly(3,4-epoxy-1-butene) (3,4-PEPB) oligomers in the presence of a cobalt-based redox catalyst was investigated. Previous studies using model compounds, 3,4-dimethoxy-1-butene and 1,4-dimethoxy-2-butene, suggested that maleation of hydroxyl-terminated 3,4-PEPB oligomers would result in more rapid crosslinking in thin films. Novel maleated oligomers offered a unique combination of both electron-rich and electron-poor olefinic sites, and quantitative maleation significantly increased the crosslinking rate of 3,4-PEPB. Efficient copolymerization between terminal maleate groups and olefinic groups in the repeating unit was proposed to account for accelerated crosslinking rates. Furthermore, the addition of novel reactive diluents, such as maleic acid mono-ethyl ester, also effectively improved the 3,4-PEPB crosslinking rate. Sol fraction measurements as a function of coating thickness revealed that the crosslinking rate versus oxygen diffusion was less significant for the maleated oligomers because of the presence of reactive electron-poor olefins. Sol fractions were constant for catalyst concentrations greater than 0.25-0.50 wt % (as compared with oligomer feed). This observation suggested that a redox process was not a dominant factor in determining crosslinking rates at various experimental conditions.