Functionalized polyethylene via acyclic diene metathesis polymerization: Effect of precise placement of functional groups

The preparation of a variety of model functionalized polyethylenes using step polymerization techniques is described. Specifically, the synthesis and preliminary thermal characterization of sequence-ordered ethylene-co-acrylate, -co-styrene, and -co-vinyl chloride polymers with precisely defined ethylene run lengths is reported. Unsaturated precursor polymers with pendant groups separated by a precise number of carbons are prepared by acyclic diene metathesis (ADMET) polymerization, which upon hydrogenation of the olefin linkages become formally ethylene/polar monomer copolymers. The only variable in the microstructure of these copolymers is the identity of the pendant group allowing the strict comparison of various "comonomers" on melting point. The synthesis of the necessary symmetric diene monomers with central pendant alkoxycarbonyl, phenyl, and chloride groups is outlined. Preliminary thermal analysis shows these copolymers to melt sharply with a trend of increased melting point depression with increasing steric bulk of the pendant group.