“…These latter two properties and the solubility can be improved by the introduction of side groups R . PNB has been characterized theoretically − on the molecular scale by a set of rotational potentials having low-energy states separated by large energy barriers. 1 Chemical structure of the hydrocarbon segment of the addition polynorbornene ( n ≈ 6000) used.…”
Section: Introductionmentioning
confidence: 99%
“…While the optical properties and chemical inertness render these materials as candidates for optical and electronic uses, polynorbornene (PNB) is not meltprocessable and possesses pronounced brittleness. These latter two properties and the solubility can be improved by the introduction of side groups R. 4 PNB has been characterized theoretically [5][6][7][8][9] on the molecular scale by a set of rotational potentials having low-energy states separated by large energy barriers.…”
The dynamics of rigid random polymer coils in dilute solution has been investigated by neutron
spin-echo (NSE) spectroscopy. The polymers used were polynorbornenes that consist of chains of the bridged
norbornene rings with hexyl (PNBH) or propyl (PNBP) side groups. These polymer molecules have large internal
rotation barriers that hinder conformational changes and give each chain a kind of individual shape memory.
Thereby the chains exhibit a dynamical stiffness that leads to a significantly retarded relaxation as compared to
flexible polyisoprene chains (PI). While the latter perfectly match the prediction of the Zimm model, the
polynorbornene spectra display the signature of a dynamical stiffness due to the “frozen” coil conformation of
the PNBH or PNBP chains.
“…These latter two properties and the solubility can be improved by the introduction of side groups R . PNB has been characterized theoretically − on the molecular scale by a set of rotational potentials having low-energy states separated by large energy barriers. 1 Chemical structure of the hydrocarbon segment of the addition polynorbornene ( n ≈ 6000) used.…”
Section: Introductionmentioning
confidence: 99%
“…While the optical properties and chemical inertness render these materials as candidates for optical and electronic uses, polynorbornene (PNB) is not meltprocessable and possesses pronounced brittleness. These latter two properties and the solubility can be improved by the introduction of side groups R. 4 PNB has been characterized theoretically [5][6][7][8][9] on the molecular scale by a set of rotational potentials having low-energy states separated by large energy barriers.…”
The dynamics of rigid random polymer coils in dilute solution has been investigated by neutron
spin-echo (NSE) spectroscopy. The polymers used were polynorbornenes that consist of chains of the bridged
norbornene rings with hexyl (PNBH) or propyl (PNBP) side groups. These polymer molecules have large internal
rotation barriers that hinder conformational changes and give each chain a kind of individual shape memory.
Thereby the chains exhibit a dynamical stiffness that leads to a significantly retarded relaxation as compared to
flexible polyisoprene chains (PI). While the latter perfectly match the prediction of the Zimm model, the
polynorbornene spectra display the signature of a dynamical stiffness due to the “frozen” coil conformation of
the PNBH or PNBP chains.
“…The second type of poly(norbornene) is a cationic or free-radical polymerization product of norbornene through 2,7-linkage, which is, however, usually formed with low molecular weights (molecular weight <1000) and low yield because of the rearrangements and transfer reactions. 1a,b,e, Driven by industrial application, the vinyl polymerization of norbornene inspired the interest of chemists and chemical engineers . V−PNB (vinylic polynorbornene), a special polymer with constrained rings in each unit, possesses interesting and unique properties such as high chemical resistance, good UV resistance, low dielectric constant, high glass transition temperature, excellent transparency, large refractive index, and low birefringence. , Such a polymerization akin to the classical olefin polymerization is termed vinyl polymerization, 1a,e in which the polymerization opens the double bond and leaves the bicyclic structural unit intact. V−PNB appeared with a TiCl 4 /Al i Bu 3 catalyst back in the early 1960s. 1a,e, Subsequently various complexes of nickel, cobalt, chromium, titanium, zirconium, and palladium have been used as catalysts for norbornene vinyl polymerization and strained cyclic olefins in general. , It was reported that the nickel(II) complexes bearing phosphoraniminato ligands had high catalytic activity for the vinyl polymerization of norbornene to produce high polymer 9l.…”
A series of neutral salicylaldiminato Ni(II) complexes have been synthesized and
characterized, and complexes a and e have been confirmed by X-ray single-crystal analyses.
These compounds show highly catalytic activities for the vinyl polymerization of norbornene
with MAO cocatalyst, which could be up to 2.86 × 108 g PNB/(mol Ni·h), and also lead to
various activities, molecular weights, and distributions of polynorbornenes under different
reaction conditions.
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