Title: carbonaceous mesophase
Long Title: IUPAC Gold Book - carbonaceous mesophase
DOI: 10.1351/goldbook.C00822
Status: current

Definition
A liquid-crystalline state of pitch which shows the optical birefringence of disc-like (discotic) nematic liquid crystals. It can be formed as an intermediate phase during thermolysis (pyrolysis) of an isotropic molten pitch or by precipitation from pitch fractions prepared by selective extraction. Generally, the spherical mesophase precipitated from a pyrolysing pitch has the Brooks and Taylor structure. With continuous heat treatment the carbonaceous mesophase coalesces to a state of bulk mesophase before solidification to green coke with further loss of hydrogen or low-molecular-weight compounds.

Note
In the formation of carbonaceous mesophase by thermolysis (pyrolysis) of isotropic molten pitch, the development of a liquid-crystalline phase is accompanied by simultaneous aromatic polymerization reactions. The reactivity of pitch with increasing heat treatment temperature and its thermosetting nature are responsible for the lack of a true reversible thermotropic phase transition for the bulk mesophase in most pitches. Due to its glass-like nature most of the liquid-crystalline characteristics are retained in the super-cooled solid state.

Related Terms
- Brooks and Taylor structure: https://goldbook.iupac.org//terms/view/B00747
- bulk mesophase: https://goldbook.iupac.org//terms/view/B00754
- extraction: https://goldbook.iupac.org//terms/view/E02301
- green coke: https://goldbook.iupac.org//terms/view/G02697
- isotropic: https://goldbook.iupac.org//terms/view/I03353
- liquid-crystalline phase: https://goldbook.iupac.org//terms/view/LT06855
- mesophase: https://goldbook.iupac.org//terms/view/M03849
- phase transition: https://goldbook.iupac.org//terms/view/P04537
- pitch: https://goldbook.iupac.org//terms/view/P04677
- polymerization: https://goldbook.iupac.org//terms/view/P04740
- precipitation: https://goldbook.iupac.org//terms/view/P04795
- pyrolysis: https://goldbook.iupac.org//terms/view/P04961
- solidification: https://goldbook.iupac.org//terms/view/S05733
- thermolysis: https://goldbook.iupac.org//terms/view/T06326
- weight: https://goldbook.iupac.org//terms/view/W06668

Source
- PAC, 1995, 67, 473. 'Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)' on page 483 (https://doi.org/10.1351/pac199567030473)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/C00822/html
- json: https://goldbook.iupac.org/terms/view/C00822/json
- xml: https://goldbook.iupac.org/terms/view/C00822/xml

Citation: Citation: 'carbonaceous mesophase' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.C00822
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Accessed: 2026-04-19T02:46:07+00:00