Wilson-Whitford, Samuel (2019) Urea and carbamate functionalities as self-associating moieties for application in reversible supramolecular polymeric drag reducers in oil. PhD thesis, University of Warwick.

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Abstract

In this thesis we look at the use of urea and carbamate functionalities for applications in selfassembled systems. The specific focus of the work is the application of these functional groups in self-assembled, reversible drag reducers for oil based solvents, namely n-alkanes, but additional applications have been found or discussed.

Firstly, bis-carbamate and bis-urea compounds were synthesised to be used as organogelators, using a selection of hydrocarbon end groups that cover n-alkyl, cyclic alkanes and aromatic functionalities. These compounds were tested as gelators in a range of polar, neutral and apolar solvents, the nature of their interactions is studied and the relative gelation efficiency in equivalent carbamate and urea molecules were compared. The aim here was to identify end groups choices for use in telechelic drag reducers. Secondly, one of these bis-carbamates, cyclohexylbiscarbamate, was applied as a droplet stabiliser due to the observed needle shape of its crystals induced by the one dimensional ladder of its crystal structure. Hydrogen bonding driven super saturation was used to form capsules with a crystal jammed shell, which allowed for size control and a thermally reversible shape control. Thirdly, self-associating end groups from the bis-urea compounds were incorporated, as functional monoisocyanates, to form telechelic, dynamically self-associative polymers with enhanced shear thinning and yield stresses, which could be enhanced further through adding a low percentage of tri-star branched units. These polymers were investigated as low molecular weight polymer drag reducers in dilute regimes in hydrocarbon solvents.

Following this, a series of functional acrylamide monomers were synthesised, using the same functional groups used in the bis-carbamate molecules. An octadecyl carbamate, phenyl carbamate and cyclohexyl carbamate acrylamide were synthesised and the nature of their interactions was explored by crystallography and NMR titration, revealing that the monomers were self-associative in apolar solvent. The kinetics of the monomer homopolymerisations were also explored. Finally, these functional acrylamides were copolymerised with a commercial oil soluble acrylamide with the aim of creating low molecular weight polymer units with pendent hydrogen bonding units. Monomer reactivity ratios and resulting copolymer composition were identified. These polymers were assessed as self-associative drag reduces in non-aqueous solvent and also tested for their thermal properties, indicating self-association in the bulk due to sizeable Tg increases with increased functional monomer content.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	Q Science > QD Chemistry
Library of Congress Subject Headings (LCSH):	Urea, Carbamates, Self-assembly (Chemistry)
Official Date:	November 2019
Dates:	Date Event November 2019 UNSPECIFIED
Institution:	University of Warwick
Theses Department:	Department of Chemistry
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Bon, Stefan Antonius Franciscus
Format of File:	pdf
Extent:	xiii, 241 leaves : illustrations, charts
Language:	eng

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