Self-assembling chiral gelators for fluorinated media.
Formulations involving partially and fully fluorinated media represent a technological challenge given the lipophobic and hydrophobic nature of such liquids. The identification of self-associating materials with which to control the viscosity and solubilizing characteristics of fluorinated solvents is a particularly interesting area of research. It is shown here that the presence of the stereogenic centers inherent in a family of bis-(alpha,beta-dihydroxy ester)s is an essential requirement for the thermoreversible gelation of mixtures of partially fluorinated liquids 2H,3H-perfluoropentane (HPFP) and 1H,1H-heptafluorobutanol (HFB). Gelation is driven by hydrogen bonding, which induces a nonpreferred conformation around the bis-(alpha,beta-dihydroxy ester) structural motif. An analysis of the melting temperature yields an enthalpy of melting that is consistent with three to four hydrogen bonds, commensurate with the end-group structure of the gelator. Small-angle neutron scattering demonstrated the existence of the common fibrillar structures whose dimensions showed no obvious correlation with the molecular structure of the gelator.
Côte
Marie
M
School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK.
Nicholls
Tim
T
Knight
David W
DW
Morgan
Ian R
IR
Rogueda
Philippe G A
PG
King
Stephen M
SM
Heenan
Richard K
RK
Griffiths
Peter C
PC
D020816:Amino Acid Motifs; D000440:Butanols / Q000737:chemistry*; D005461:Fluorine / Q000737:chemistry*; D005782:Gels; D006860:Hydrogen Bonding; D008956:Models, Chemical; D015233:Models, Statistical; D009502:Neutrons; D012542:Scattering, Radiation; D012997:Solvents / Q000737:chemistry; D013237:Stereoisomerism; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors
D000440:Butanols; D005782:Gels; D012997:Solvents; D005461:Fluorine