Influence of Tacticity on the Crystal Structures of Hydrogenated Ring-Opened Poly(norbornene)s

Abstract

The crystal structures of highly crystalline isotactic and syndiotactic hydrogenated poly(norbornene)s [Hpoly(NB)s], synthesized by the stereospecific ring-opening metathesis polymerizations of norbornene followed by complete hydrogenation, have been determined for the first time on the basis of the X-ray diffraction data analyses. The similarity and difference of the chain conformation and the chain packing mode in the crystal lattice have been clarified among the three kinds of H-poly(NB) samples (syndiotactic, isotactic, and atactic species). The molecular chains were found to take essentially the planar zigzag conformation at room temperature with slight torsional angle fluctuations around the skeletal C−C bonds. The cyclopentylene rings were found to protrude from the plane of the skeletal polymer chain in various different ways depending on the tacticity, resulting in the difference of the whole shape of the chains and then the difference of the chain packing structure. The melting point was found to be different depending on the tacticity: 178, 148, and 134 °C for the isotactic, atactic, and syndiotactic H-poly(NB)s, respectively. The difference in the thermal behavior has been discussed qualitatively on the basis of these structural pieces of information.

Synthesis and properties of cyclic olefin polymers by ring-opening metathesis (co)polymerization of α-methyl-substituted norbornene lactones

“…5 shows the powder XRD patterns of the three copolymers compared with the homopolymers, amorphous H-poly( endo -MNBL) (Fig. 5a) and crystalline H-poly(NB) 32 (Fig. 5e), which shows 2 θ peak tops at 15.8 and 18.4, respectively.…”

Frontal polymerization-triggered simultaneous ring-opening metathesis polymerization and cross metathesis affords anisotropic macroporous dicyclopentadiene cellulose nanocrystal foam

“…Therefore, changing the tacticity of polymerizing monomer by controlling the C=C bond stereochemistry or by using robust initiators were favorable measures of preventing pDCPD oxidation 36 , 62 . So far, hydrogenation was successful in enhancing the oxidation resistance of, for example, low-crosslinked pDCPD aerogels 63 and ROMP-mediated norbornene polymers 64 . This effect was corroborated by a recent study by Y. Nakama et al 64 from which a strong correlation between oxidation resistance and the changes induced to the chain conformations or packing modes in crystal lattices was confirmed by the wide-angle x-ray diffraction measurement.…”

“…So far, hydrogenation was successful in enhancing the oxidation resistance of, for example, low-crosslinked pDCPD aerogels 63 and ROMP-mediated norbornene polymers 64 . This effect was corroborated by a recent study by Y. Nakama et al 64 from which a strong correlation between oxidation resistance and the changes induced to the chain conformations or packing modes in crystal lattices was confirmed by the wide-angle x-ray diffraction measurement. Based on these findings, our group sought to investigate the nanoscale effect of ACs to the development of the DCPD/AC foam crystal structures.…”

Asymmetric Molecular Dynamics and Anisotropic Phase Separation in the Cocrystal of the Crystalline/Crystalline Polymer Blend

“…In recent years, novel polyolefins, stereoregular hydrogenated polynorbornene (hPNB)­s, in addition to an existing stereoirregular one, , were successfully synthesized via stereoselective ring-opening polymerization. Interestingly, all s -, i -, and atactic ( a )-hPNBs crystallize in monoclinic ( a = 5.97 Å, b = 9.48 Å, c = 12.58 Å, and β = 60°), orthorhombic ( a = 5.95 Å, b = 8.25 Å, c = 12.65 Å), and monoclinic lattices ( a = 5.43 Å, b = 9.45 Å, c = 12.41 Å, and β = 90°), respectively, where all three adopt a nearly trans -conformation ( c = 12.41–12.65 Å) independent of stereoregularity . Moreover, Kafle et al reported that (i) s - and i -hPNBs are fixed crystals, while a -hPNB conducts large amplitude motions associated with a crystal–crystal transition into the rotator phase (mobile crystal) at T cc = 115 °C, and (ii) a -hPNB shows a much higher crystallinity (Φ c = 82%) and a much longer long period ( L = 80 nm) than those for stereoregular ones (Φ c = 50–55% and L = 17–21 nm) .…”

“…13 C CSA spectra for (b, c) C7 and (d, e) C1,4 signals for pure a - (red) and s -hPNBs (blue) and their blend (green) measured by using SUPER at 25 and 123 °C and (b, c) simulated CSA patterns (dashed lines) for pure a - (red) and s -hPNBs (blue) and the blend (green). (b) Chain conformation for pure a - and s -hPNBs determined in ref and their dynamic models with orientations for the CSA principle axes on the C7 carbon …”