Thermolysis Temperatures Research Articles

Low temperature thermal behaviour of lipopolysaccharides from Brucella and other Gram-negative bacteria

In lipopolysaccharides (LPSs) from Brucella and other Gram-negative bacteria, cooling to temperatures between −13 and −36°C gives rise to a phase transition between different ordered supramolecular arrangements. During a subsequent heating program in DSC, the thermal effect temperatures that show the phase transition for each LPS are in inverse relationship with their respective thermolysis temperatures. Both effects, thermolysis and cooling phase transition, have been related to the relative strength of the linkage types in the O-change structure and to the facilities for intermolecular hydrogen bonding.

Thermally Depolymerizable Polycarbonates V. Acid Catalyzed Thermolysis of Allylic and Benzylic Polycarbonates: A New Route to Resist Imaging

Polymers containing allylic and benzylic carbonate repeating units have been prepared by phase-transfer catalyzed polycondensation of activated bis-carbonates or carbamates and diols. The polymers are highly susceptible to thermal depolymerization and revert to small molecules when heated to temperatures which vary from 140 to 230°C depending on structure. The thermolysis temperatures are reduced to well below 100°C if catalytic amounts of acid are added to the polycarbonates. The thermolysis or acidolysis of bis allylic or benzylic carbonates provides a convenient route to aromatic compounds as demonstrated with both models and polymers. The polycarbonates can be used to formulate highly sensitive resist materials with potential for self-development of positive images. Some benzylic polycarbonates which produce polymerizable divinyl monomers upon thermolysis can be used to create negative images in a process which includes both depolymerization and photocrosslinking.

Gas-phase thermolysis of a thioketen-S-oxide

The unimolecular gas-phase thermolytic decomposition of 1,1,3,3-tetramethyl-2-thiocarbonylcyclohexane S-oxide (3) has been studied as a function of temperature by a flash vacuum thermolysis (f.v.t.) technique. The products detected are the carbenes (4) and (5), the ketone (6), the keten (7), the thioketone (8), and the thioketen (9). The product ratio is highly dependent on the thermolysis temperature. The thermolysis of (3) is mechanistically rationalized by assuming the existence of only two concurrent primary processes, which are (a) extrusion of atomic oxygen, leading to the thioketen (9), and (b) electrocyclic ring closure into the corresponding three-membered oxathiiran (10). The latter is dominant at lower temperatures, whereas higher thermolysis temperatures favour atomic oxygen extrusion. At further elevated temperatures additional concurrent primary reactions, i.e. extrusions of SO and CSO leading to the carbenes (5) and (4), respectively, are observed. Owing to an apparently very short half-life of the oxathiiran (10), only the decomposition products of the three-membered ring compound have been detected. These are the thioketone (8), formed by rearrangement of (10) into the α-thiololactone (11) followed by loss of CO, minor amounts of the ketone (6), formed analogously, and the keten (7), as a result of simple sulphur extrusion.