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

The preparation of a variety of model functionalized polyethylenes using st ep polymerization techniques is described. Specifically, the synthesis and preliminary thermal characterization of sequence-ordered ethylene-co-acryla te, -co-styrene, and -co-vinyl chloride polymers with precisely defined eth ylene run lengths is reported. Unsaturated precursor polymers with pendant groups separated by a precise number of carbons are prepared by acyclic die ne metathesis (ADMET) polymerization, which upon hydrogenation of the olefi n linkages become formally ethylene/polar monomer copolymers. The only vari able in the microstructure of these copolymers is the identity of the penda nt 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. Prelimina ry thermal analysis shows these copolymers to melt sharply with a trend of increased melting point depression with increasing steric bulk of the penda nt group.