The preparation and characterization of linear and cross-linked poly(fluorenyl)
Conference
·
OSTI ID:459347
- Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.
Retrogressive reactions in coal processing are that class of reactions that lead to the formation of high molecular weight materials that are more intractable than those present in the coal prior to processing. This outcome almost always is regarded as deleterious. The present work focuses on the characterization of the acid-catalyzed polymerization of benzylic fluorides, and in particular the synthesis of poly(fluorenyl), as an example of the type of chemistry that may occur in the cross-linked organic matrix of coals when in contact with strong acids. Solution and solid state {sup 13}C NMR spectroscopy was used to characterize the soluble and insoluble polymers. The change in the value of the fraction of aromatic carbon that is protonated is the criterion used to monitor the extent of cross-linking in these polymer preparations. Benzylic fluorides are sensitive substances, prone to further reaction via acid catalyzed heterolytic scission of the C-F bond. The electron deficient reactive intermediate formed in this reaction undergoes electrophilic aromatic substitution. This reaction can be started with catalytic traces of acid and is self-sustaining as HF is generated in equivalent concentrations as the reaction proceeds. The relevance of this naturally non-occurring functional group in coal processing stems from the similar reaction pathway followed by both benzylic fluorides and benzylic alcohols. In the coal matrix, the operation of two exogenous processes--air oxidation and strong acid treatment of the coal (demineralization) creates a situation in which the polymerization discussed herein may occur in the coal. In addition to the polymerization reactions that produce poly(fluorenyl), the subsequent cross-linking of the linear polymer is also reported. In subsequent work, similar chemistry will be applied to soluble lignin as a model more similar to low rank coals.
- Research Organization:
- Oak Ridge National Lab., TN (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 459347
- Report Number(s):
- CONF-970443--12; ON: DE97004110
- Country of Publication:
- United States
- Language:
- English
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