While the NMR features for poly(1,2-azaborinine)s 2 and 2-Z are distinct, very similar FT-IR features were seen for the isomeric polymers as illustrated above. To further verify the preferential incorporation of cis-linkages for polymer 2-Z we also acquired Raman data for both polymers. Because of the different selection rules, Raman is uniquely able to distinguish between E-and Z-olefin incorporation into the backbone of polymers such as poly(butadiene) rubbers of polynorbornene. Raman spectra were acquired by excitation with a 785 nm laser. The region for the olefinic signals is illustrated in Figure . The bands for the C=C stretching modes are expected around 1640-1680 cm -1 and those for the olefinic C-H bending in the region of 1250-1320 cm -1 . While differences in the intensity of the bands in these regions are apparent for 2 and 2-Z, signal overlap prevented a quantitative analysis. Nevertheless, collectively, the NMR, IR and Raman data strongly support the unique structure with four-membered B-N heterocycles embedded in the backbone of a ROMP-derived polyolefin. In conclusion, we have successfully synthesized the first example of a Dewar-azaborine polymer (2) by ROMP of Dewar isomer 1 with Grubbs and Hoveya-Grubbs 2 nd generation catalysts, as well as a Z-selective catalyst. While several azaborinine-derived polymers have recently been reported as analogs of common carbon-based polymers such as polyphenylene, polystyrene, and polyvinyl naphthalene, 12b, 19a, 23 the structure of polymers 2 and 2-Z containing 4-membered B-N heterocycles is unprecedented. Successful formation of 2 was verified by GPC, 2D NMR, and FT-IR, and the differences in regiochemistry for the Zselective catalyst were further evaluated by 2D NOESY and Raman measurements. Recent studies by Klausen, Ouchi and others demonstrate the great promise of polymers with B substituents and B-N units in the pursuit of novel polyolefins with polar functional groups through post-modification methods. 12c, 23h, In a similar vein, we anticipate that the presence of the B-N four-membered rings may be exploited in the preparation of new functional polymers that contain both amine and hydroxyl side groups via chemoselective organoborane oxidation 8 and/or hydrogenation of the double bonds in the backbone.