Norbornene

About: Norbornene is a research topic. Over the lifetime, 5628 publications have been published within this topic receiving 104495 citations. The topic is also known as: norbornylene & norcamphene.

Ethene/Norbornene Copolymerization with Palladium(II) α‐Diimine Catalysts: From Ligand Screening to Discrete Catalyst Species

Abstract: Sixteen palladium(II) alpha-diimine catalysts were investigated in a screening-like procedure for the copolymerization of ethene with norbornene. The resulting copolymers were characterized by (13)C NMR spectroscopy, differential scanning calorimetry, gel permeation chromatography, and viscosimetry. The degree of incorporation of norbornene in the polymer chain is very high for most of the catalysts. To validate the results achieved in the screening, two catalysts, [[ArN=CHCH=NAr]Pd(Me)(CH(3)CN)]BAr(f) (4) (1 b'; Ar=2,6-Me(2)C(6)H(3), BAr(f) (4)=B[3,5-C(6)H(3)(CF(3))(2)](4)) and [[ArN=C(CH(3))C(CH(3))=NAr]Pd(Me)(CH(3)CN)]BAr(f) (4) (2 c'; Ar=2,6-iPr(2)C(6)H(3)), were synthesized as discrete catalytically active species, and their copolymerization behavior was investigated in detail. In agreement with the screening results, 1 b' incorporates norbornene much better in the polymer chain than ethene, a property that has no analogue in metallocene catalysts.

Quantitative Determination of the Chemical Composition of Silica−Poly(norbornene) Nanocomposites

Abstract: Nanoparticle hybrid materials consisting of a silica core surrounded by a poly(norbornene) brush have been prepared by ring opening metathesis polymerization (ROMP). A quantitative determination of each stage of composite formation has been accomplished, including a determination of the density of surface-bound functional groups, catalyst molecules, and polymer chains. This analysis has enabled the determination of the reaction efficiency between the catalyst and the surface-bound functional groups as well as the determination of the fraction of metal-mediating species that initiate a polymer chain. Control of the chain density was demonstrated by two methods: the use of controlled reaction times between the catalyst and the surface, and the variation of the surface functional group density. Polymer chain densities resulting from composites prepared with different tether structures will also be reported. The resulting brush densities were found to span a wide range, including those previously reported for polymer layers formed by adsorption, grafting of preformed polymer chains, and surface-initiated polymerization (SIP).

Well-Defined Redox-Active Polymers and Block Copolymers Prepared by Living Ring-Opening Metathesis Polymerization

Abstract: Mo(CH-t-Bu)(NAr)(O-t-Bu){sub 2} (1a) in Thf/0.1 M [n-Bu{sub 4}N]AsF{sub 6} is not oxidized at potentials up to 1.0 V and undergoes a reversible, one electron reduction at -2.16 V vs SCE at a Pt electrode. An analogous intiator containing a ferrocenylmethylidene ligand (1b) can be synthesized by treating 1a with vinylferrocene. Redox-active derivatives of norbornene, containing ferrocene (2) or phenothiazine (3), were prepared and polymerized by 1a or 1b to give living block copolymers containing the ring-opened norborene derivatives. The living polymer was cleaved from the metal in a Wittig-like reaction with pivaldehyde, trimethylsilylbenzaldehyde, or octamethylferrocenecarboxaldehyde. Polydispersities for the longer block copolymers containing up to {approximately}90 monomer units were found to be as low as 1.05 by GPC. In one case the polydispersity of a homopolymer made from the ferrocene-containing monomer was determined by FD-mass spectroscopy to be 1.06. DSC studies suggest that microphase studies of homo and block copolymers showed that the redox centers were electrochemically independent and that all centers exchanged electrons with the electrode. Neutral polymers became insoluble upon oxidation to a polycation, yielding an adsorbed polymer layer on the electrode that could then be cathodically stripped. This oxidative deposition process depended on the electrolyte and the polymermore » molecular weight but also could be controlled by the size of a nonelectroactive block in the block copolymers. Problems resulting from precipitation of the redox polymers could be circumvented by employing normal pulse voltammetry. Polymers containing redox centers in both end groups as well as in the polymer chain itself have been prepared and their nature confirmed in electrochemical studies.« less