Ring-opening metathesis polymerization (ROMP) involving 8-membered cyclic olefins, such as the parent molecules cis-cyclooctene (COE) and cis,cis-1,5-cyclooctadiene (COD), leads to various polyalkenamers that have broad potential in a variety of fields. The use of different catalysts and diverse functionalized monomers allows for control over molar mass and architecture in the resultant polymers. We review the ROMP of unsubstituted and substituted COE and COD to tune the properties of the resultant homopolymers and copolymers. Starting with a survey of homopolymers, we report the strengths and limitations of the ROMP of functionalized 8-membered ring olefins. Then we show how these monomers are used to control crystallinity, hydrophobicity and morphology, in various types of copolymers.

A variety of multisubstituted cyclooctenes were prepared and employed as monomers for ring-opening metathesis polymerization using the Grubbs second or third generation catalysts. The resulting polymers were characterized by NMR spectroscopy, size exclusion chromatography, and differential scanning calorimetry. Monomers possessing a substituent at the 3-position afforded highly regio- and stereoregular polyalkenamers, from which the corresponding sequence-specific vinyl quaterpolymers were obtained upon hydrogenation. Simultaneous control of tacticity was also demonstrated by employing monomers with defined stereochemistry.

Tensile tests were conducted on a Rheometrics Scientific Minimat Instrument at a crosshead extension rate of 10 mm/min at room temperature. Dogbone samples (8 mm gage length, 0.5 mm gage thickness, 3 mm gage width) were prepared by stamping of compression molded film.Reported values are averages and standard deviations of four or five samples (see Figure S60 and S61).Wide-angle X-ray scattering (WAXS) measurements were performed on a Bruker D8 Discover diffractometer using a Cu Kα radiation point source. The data was collected and analyzed by Bruker GADDS software.Computational Methods. Calculation were performed at M06-2X/SDD|6-311+G(2df,p) // M06-L/SDD|6-31G(d) level of theory 3 with Gaussian 09 revision A.02. 4 Analytic frequency calculations were done for all structures in order to characterize their nature as either minima or TS structures, and also to compute thermal contributions to enthalpy and free energy. The effect of solvation by CHCl3 was computed from the SMD continuum solvation model. 5 Composite free energies in solution were computed by summing gas-phase M06-L thermal contributions with single point SMD/M06-2X single-point energies. Correction from the gas phase to the solution was made by adding -1.9 kcal/mol (RT Ln ([Sln]/[Gas])) to the free energy of each molecule.

We demonstrated that the ring-opening metathesis polymerization (ROMP) of 3-substituted cyclooctenes bearing polar substituents allows the synthesis of highly regio-and stereo-regular polymers. A series of polyalkenamers with 90-99 % head-to-tail/trans configuration were synthetized in good yields (33-87 % yield). Upon saturation of the backbone using diimide, these polymers represent a class of linear polyethylene derivatives where the polar side chain is located on every eighth carbon. The thermal properties of both the saturated and unsaturated polymers depend strongly on the size and polarity of the functional side groups. The results presented here demonstrate that the 3-substituted cyclooctenes can be used not only for the synthesis of precisely functionalized polyethylene derivatives, but also to participate in the ringopening metathesis copolymerization with unfunctionalized cyclic olefins to generate copolymers with tunable properties.

Cross metathesis of polymers made from 3-substituted cyclooctene derivatives produce regio- and stereoregular block and hetereotelechelic polymers.