Otsuka, H.; Muta, T.; Sakada, M.; Maeda, T.; Takahara, A. Scrambling reaction between polymers prepared by step-growth and chain-growth polymerizations: macromolecular cross-metathesis between 1,4-polybutadiene and olefin-containing polyester Chem. Commun., 2009, 1073-1075.
Each polymerization method tends to offer its own rules and limitations for control of polymer architecture, but Otsuka and Takahara recently published an interesting preliminary report that uses olefin cross metathesis to hybridize the polymer structures of two olefin-containing polymers generated by very different polymerization mechanisms. The authors generated two homopolymers: a linear polybutadiene (generated according to a chain-growth mechanism by ROMP of 1-5-cyclooctadiene), and an olefin-containing polyester (generated according to a step-growth polycondensation of cis-butene-diol with adipoyl chloride). These two very different polymer architectures were then hybridized by cross metathesis of the internal olefins of the two types of macromolecules with a 1st generation Grubbs catalyst. Analysis by DSC and NMR showed that the two homopolymers scrambled to give a random copolymer of oligomeric butadienes and oligoesters, and that the degree of polymer exchange was governed by metathesis reaction time. This study offers a reminder that ROMP is not the only way that metathesis can be used to generate the perfect polymer for any job.