Ulfert E. Wiersum

Cyclopent[a]indene (benzopentalene) : generation by flash vacuum pyrolysis and subsequent dimerisation.

Abstract Cyclopent[ a ]indene (benzopentalene, 7 ) is generated by flash vacuum pyrolysis of 3-phenylphthalic anhydride ( 6 ), biphenylene ( 3 ) or diphenic anhydride ( 4 ). It dimerises readily and adds cyclopentadiene above −70 °C, but it does not equilibrate at 900 °C with as -indacene ( 1 ).

Thermolysis of benzo[c]phenanthrene: Conversion of an alternant C18H12 PAH into Non-alternant C18H10 PAHs

Abstract The product composition of the pyrolysates obtained upon thermolysis of the alternant C18H12 PAH benzo[c]phenanthrene (1) is markedly pressure dependent. At 0.1–0.5 Torr (N2 carrier gas, 1050–1150 °C) 1 is converted into the non-alternant C18H10 PAHs cyclopenta[cd]pyrene (4) and benzo[ghi]fluoranthene (5) which have been identified as abundant combustion effluents and are associated with fullerene formation.

Flash vacuum thermolysis of biphenylene and diphenic anhydride. Formation of 6b,7,10,10a-tetrahydro-as-indaceno[1,8-jkl]fluoranthene. Evidence for the intermediacy of as-indacene on the C12H8 potential energy surface.

Flash Vacuum Thermolysis (FVT) of biphenylene (1) and of diphenic anhydride (2) at 900 °C gave acenaphtylene (10), exo- and endo-6b,7,10,10a-tetrahydro-as-indaceno[1,8-jkl]fluoranthene (11) in high yield. The isolation of compound 11 provides evidence for the occurrence of the anti-aromatic as-indacene (8) on the C12H8 potential energy surface

Formation of monomeric halogenoaryl acrylates in the presence of hindered pyridine bases

Abstract Acylation of perhalogenophenols and pyridinols by acryloyl chloride in the presence of hindered pyridines, such as 2,6-lutidine, afforded the corresponding acrylates which were isolated in a pure form by chromatography on a Florisil® column. This was performed without in situ polymerization of the corresponding acrylates.

Low-loss nonlinear optical polymeric waveguide materials and devices

Recently developed photobleachable polymers show a loss of < 0.1 dB/cm at 1300 nm and < 0.15 dB/cm at 1550 nm. Nonchromophore containing polymers show film waveguide losses of < dB/cm at 1300 nm and 1550 nm. Refractive indices in these materials can be tuned within a range of 0.05 by changing the polymer composition. Multilayers of cross-linked (solvent resistant) layers, each 2-10 microns have been deposited by multiple spinning steps. Using these multilayers, fully embedded, fiber-compatible strip waveguide structures have been created by masked bleaching of multilayers with chromophore containing corelayers. The lateral refractive index contrast is thereby tuned by changing the chromophore content of the corepolymer. Poling-induced loss has been investigated by wavelength and polarization dependent measurements of losses in films. The results indicate that this loss is due to increased scattering. Bleached channel waveguides in a poled (at 125 V/micrometers ) nonlinear optical polymer have been made showing losses of < dB/cm at 1300 nm. Rapid photodegradation at 1300 nm has been observed in stilbene containing channel waveguides. In a nitrogen atmosphere no degradation was seen. The same is true for waveguides in air at 1550 nm. This suggests the attack of the stilbene chromophores by singlet oxygen. Therefore a new generation of low-loss, linear, and nonlinear optical polymers based on singlet oxygen resistant molecules has been developed. The linear optical polymers are used for the realization of low-insertion loss (< 2 dB), digital (switch voltage 3-6 V) and efficient (switching power < mW, cross talk - 20 dB) pigtailed and packaged 1 X 2 switches. They utilize the strong thermo-optic effect in polymers. Their switching time is therefore limited to 1 ms whereas their polarization dependence is < 0.3 dB.

Flash vacuum thermolysis of 2-bromoethanol. Formation of α-bromoethylethers via 1-bromoethanol

Abstract Flash Vacuum Thermolysis of 2-bromoethanol ( 2 ) leads to the quantitative formation of 1-bromo-1-(1-bromoethoxy)ethane ( 5 , di-α-bromoethylether). Low temperature IR spectroscopy shows that 5 arises from the dimerization of 1-bromoethanol ( 3 ), which is observed below -100°C as the primary product.

Preparative flash vacuum thermolysis. Conversion of triphenylene to cyclopent[h,i]acephenanthrylene. A significant reaction for environmental science and combustion research

Cyclopent[h,i]acephenanthrylene is selectively formed upon flash vacuum thermolysis at 1000 °C of triphenylene; the reaction represents a novel mechanistic route in combustion, giving rise to a cyclopentapolyaromatic compound.