Precision ethylene-styrene copolymers through the ring opening metathesis polymerization of 3-phenyl cyclododecenes

Synthesis of sequence-controlled poly(ethylene-co-styrene) copolymers is challenging due to the limitations associated with inherent reactivity ratios for ethylene and styrene in catalytic olefin polymerizations. An alternative method to generate ethylene copolymers is ring-opening metathesis polymerization (ROMP) of cyclic olefins followed by hydrogenation, in which a substituted cycloalkene yields polymers analogous to those from copolymerizations of two distinct monomers after post-polymerization hydrogenation. In certain cases, regioregularity (and thus sequence specificity) of these "copolymers" can be realized if the approach of the metathesis catalyst to the monomer occurs regioselectively. In this work, precision polyolefin copolymers were synthesized by ROMP of phenyl-substituted cyclododecenes and subsequent hydrogenation. The effects of the chain transfer agent, monomer structure, target molar mass and reaction conditions on regioselectivity were investigated using H-1 and C-13 NMR spectroscopies. These investigations of the ROMP of low-strain cyclododecenes provided useful information for the fundamental understanding of mechanistic aspects of the polymerization. Hydrogenation of the polydodecenamers afforded linear low density polyethylenes with a phenyl side chain every twelve backbone carbons.